Other than using optical filters, White balance is the primary means of controlling color in a digital camera. Normal, Vivid and Neutral color settings control the saturation level of color, but white balance controls the hue or color cast of the image. Cameras which allow you to set the color temperature by degrees Kelvin and the tint by increments of magenta and green offer the most control. The color model of digital cameras is based on L*a*b* color, which uses two opponent color channels, one corresponding to temperature and the other to tint.
News, Muse and Reviews for Aspiring Lensmen.
Showing posts with label Post-Processing Basics. Show all posts
Showing posts with label Post-Processing Basics. Show all posts
Saturday, June 2, 2012
Wednesday, January 4, 2012
Basic Contrast Adjustments
Exposure does have an effect on contrast, but generally it’s governed by the lens, film and lighting.
Contrast can also be controlled through the chemistry, materials, techniques and algorithms used in processing and printing. Digital images are processed either in the camera or the lightroom, so contrast adjustments can be made at the time of exposure or during post-processing. When you adjust the contrast in a digital camera, you’re altering how the raw image from the sensor is processed just before it’s saved to memory.
Contrast is the relationship between the light and dark tones of an image. The further apart these values, the more contrast or separation the image is said to have.
Vibrancy is an attribute of color that is also related to contrast. Images with more contrast are naturally more vibrant. Generally speaking, a lens with higher contrast will also render more vibrant color. However, digitally, we can control contrast without affecting vibrancy.
Brightness/Contrast
Perhaps the simplest tool for adjusting contrast is the Brightness/Contrast panel. Unfortunately, it’s also the most misunderstood amongst professional color retouchers.
In earlier versions of Photoshop, B/C was strictly a linear adjustment, however, in recent versions it’s been changed to a gamma adjustment, with a check box to revert back to the “legacy” linear algorithm. Combined with the Luminosity mode and the Blend If sliders, this adjustment panel is an effective means of making basic contrast adjustments.
Dragging the contrast slider to the right lightens the quarter tones and darkens the three-quarter tones, increasing the contrast and vibrancy to an image with a normal distribution of tones. Conversely, dragging to the left decreases contrast and vibrancy. For lighter or darker images, the Brightness slider can be used to vary the “center” of the adjustment, similar to a “parametric” equalizer. This then compensates for high-key or low-key images, and the primary reason these two closely-related adjustments appear in the same panel.
Contrast can be controlled independently of vibrance by using the Luminosity blend mode.
Vibrance can be controlled independently of contrast by using the Color blend mode. When used this way, the Brightness and Contrast sliders each have a different effect on color saturation, without affecting lightness.
Contrast can also be controlled through the chemistry, materials, techniques and algorithms used in processing and printing. Digital images are processed either in the camera or the lightroom, so contrast adjustments can be made at the time of exposure or during post-processing. When you adjust the contrast in a digital camera, you’re altering how the raw image from the sensor is processed just before it’s saved to memory.
Contrast is the relationship between the light and dark tones of an image. The further apart these values, the more contrast or separation the image is said to have.
Vibrancy is an attribute of color that is also related to contrast. Images with more contrast are naturally more vibrant. Generally speaking, a lens with higher contrast will also render more vibrant color. However, digitally, we can control contrast without affecting vibrancy.
Brightness/Contrast
Perhaps the simplest tool for adjusting contrast is the Brightness/Contrast panel. Unfortunately, it’s also the most misunderstood amongst professional color retouchers.
In earlier versions of Photoshop, B/C was strictly a linear adjustment, however, in recent versions it’s been changed to a gamma adjustment, with a check box to revert back to the “legacy” linear algorithm. Combined with the Luminosity mode and the Blend If sliders, this adjustment panel is an effective means of making basic contrast adjustments.
Dragging the contrast slider to the right lightens the quarter tones and darkens the three-quarter tones, increasing the contrast and vibrancy to an image with a normal distribution of tones. Conversely, dragging to the left decreases contrast and vibrancy. For lighter or darker images, the Brightness slider can be used to vary the “center” of the adjustment, similar to a “parametric” equalizer. This then compensates for high-key or low-key images, and the primary reason these two closely-related adjustments appear in the same panel.
Contrast can be controlled independently of vibrance by using the Luminosity blend mode.
Vibrance can be controlled independently of contrast by using the Color blend mode. When used this way, the Brightness and Contrast sliders each have a different effect on color saturation, without affecting lightness.
Basic Exposure Adjustments
Exposure, brightness, lightness, and luminosity all describe the same basic concept, how light or dark an image appears. However, in real-world application, they’re not the same.
Exposure takes place in the camera, and once it happens, it can never really be adjusted. That said, most post processing applications have an exposure adjustment to simulate the effects of exposure. Exposure is more or less “linear”; the more light you let into the camera, the whiter the whites will become until they “wash out” and all detail is lost. However, film also has response curve. Therefore, adjusting exposure is tricky in post processing.
Brightness refers not only to luminosity, but to color as well. An image is considered to “bright” when it’s both light and has clean, vibrant colors, in other words good color saturation. The luminosity level may be perfect, but if the colors do not have adequate saturation, the image will appear dull.
Lightness refers only to luminosity, hence the “Lightness” channel in the L*a*b* color space. When the color is right, we want to be able to control only the lightness, and this is not something that can be done by adjusting exposure.
Luminosity generally refers only to lightness, and not to color. The Luminosity blend mode in Photoshop restricts an adjustment to the information that would appear in the Lightness channel of a L*a*b* image. However, used descriptively it can also refer to brightness. A “luminous” image is one that is both light and colorful.
So while this tutorial is named “Basic Exposure Adjustments” we will also talk about adjusting the brightness, lightness and gamma of an image.
Brightness/Contrast
Perhaps the simplest and most powerful tool for adjusting exposure is the Brightness/Contrast panel. Unfortunately, it’s also the most misunderstood amongst professional color retouchers.
In earlier versions of Photoshop, B/C was strictly a linear adjustment, much like adjusting exposure in a camera. However, in recent versions, this has been changed to a gamma adjustment, with a check box to revert back to the “legacy” linear algorithm. This combined with the fact that we can use it with the Luminosity mode and the Blend If sliders makes it much more powerful that it initially appears.
Drag the Brightness slider to the right to brighten or lighten the image or to the left to subdue or darken the image. The Contrast slider makes the adjustment behave similar to Curves, and is discussed in Intermediate Contrast Adjustments.
Keep in mind that color saturation is naturally dependent on luminosity, so beyond a certain point, colors may appear washed out. If this occurs, use the Luminosity mode to regain vibrance.
Exposure or “brightness” of the image, can be adjusted with Brightness/Contrast by checking the “Legacy” box. This will create a linear adjustment that shifts all the values in the image toward the highlights. When doing this, we have to be sure not to shift them so far that the highlights wash out. Once we reach that point, we can go no further.
Midtone Gamma is adjusted when the exposure is correct (the highlights of the image are matched to the “white point” of the color space) but the image needs to be lightened or brightened. To adjust the gamma, be sure to uncheck the “Legacy” box. If you want only to lighten the image, and not brighten it (affect color), then use it with the Luminosity blend mode. If you are adjusting a CMYK image, the Luminosity mode must usually always be used in order to maintain color balance.
Lightness can be adjusted by using the Luminosity blend mode with the Legacy box unchecked (gamma adjustment) or checked (linear adjustment).
Brightness can be adjusted (gamma or linear) by using the Normal blend mode. For stronger brightness adjustment with more control over hue, saturation and contrast see Advanced Exposure Adjustments.
Levels
If you need to set the white and black points (“endpoints”) of an image, Levels can be used to adjust brightness or lightness at the same time. Drag the midtone gamma slider (gray) to the left to increase the gamma (lighten the image) or to the right to decrease the gamma (darken the image). Levels can be used with the Normal or Luminosity modes, but CMYK image almost always require Luminosity to maintain correct color balance.
Exposure
The exposure sliders found in Adobe Camera Raw, Adobe Lightroom and Apple Aperture all use algorithms specifically designed to simulate the effects of exposure adjustment within the camera. They are calibrated in stops rather than arbitrary numbers, and are fairly accurate, although their effects will vary widely between applications. They are arguably the best means of adjusting exposure.
Exposure takes place in the camera, and once it happens, it can never really be adjusted. That said, most post processing applications have an exposure adjustment to simulate the effects of exposure. Exposure is more or less “linear”; the more light you let into the camera, the whiter the whites will become until they “wash out” and all detail is lost. However, film also has response curve. Therefore, adjusting exposure is tricky in post processing.
Brightness refers not only to luminosity, but to color as well. An image is considered to “bright” when it’s both light and has clean, vibrant colors, in other words good color saturation. The luminosity level may be perfect, but if the colors do not have adequate saturation, the image will appear dull.
Lightness refers only to luminosity, hence the “Lightness” channel in the L*a*b* color space. When the color is right, we want to be able to control only the lightness, and this is not something that can be done by adjusting exposure.
Luminosity generally refers only to lightness, and not to color. The Luminosity blend mode in Photoshop restricts an adjustment to the information that would appear in the Lightness channel of a L*a*b* image. However, used descriptively it can also refer to brightness. A “luminous” image is one that is both light and colorful.
So while this tutorial is named “Basic Exposure Adjustments” we will also talk about adjusting the brightness, lightness and gamma of an image.
Brightness/Contrast
Perhaps the simplest and most powerful tool for adjusting exposure is the Brightness/Contrast panel. Unfortunately, it’s also the most misunderstood amongst professional color retouchers.
In earlier versions of Photoshop, B/C was strictly a linear adjustment, much like adjusting exposure in a camera. However, in recent versions, this has been changed to a gamma adjustment, with a check box to revert back to the “legacy” linear algorithm. This combined with the fact that we can use it with the Luminosity mode and the Blend If sliders makes it much more powerful that it initially appears.
Drag the Brightness slider to the right to brighten or lighten the image or to the left to subdue or darken the image. The Contrast slider makes the adjustment behave similar to Curves, and is discussed in Intermediate Contrast Adjustments.
Keep in mind that color saturation is naturally dependent on luminosity, so beyond a certain point, colors may appear washed out. If this occurs, use the Luminosity mode to regain vibrance.
Exposure or “brightness” of the image, can be adjusted with Brightness/Contrast by checking the “Legacy” box. This will create a linear adjustment that shifts all the values in the image toward the highlights. When doing this, we have to be sure not to shift them so far that the highlights wash out. Once we reach that point, we can go no further.
Midtone Gamma is adjusted when the exposure is correct (the highlights of the image are matched to the “white point” of the color space) but the image needs to be lightened or brightened. To adjust the gamma, be sure to uncheck the “Legacy” box. If you want only to lighten the image, and not brighten it (affect color), then use it with the Luminosity blend mode. If you are adjusting a CMYK image, the Luminosity mode must usually always be used in order to maintain color balance.
Lightness can be adjusted by using the Luminosity blend mode with the Legacy box unchecked (gamma adjustment) or checked (linear adjustment).
Brightness can be adjusted (gamma or linear) by using the Normal blend mode. For stronger brightness adjustment with more control over hue, saturation and contrast see Advanced Exposure Adjustments.
Levels
If you need to set the white and black points (“endpoints”) of an image, Levels can be used to adjust brightness or lightness at the same time. Drag the midtone gamma slider (gray) to the left to increase the gamma (lighten the image) or to the right to decrease the gamma (darken the image). Levels can be used with the Normal or Luminosity modes, but CMYK image almost always require Luminosity to maintain correct color balance.
Exposure
The exposure sliders found in Adobe Camera Raw, Adobe Lightroom and Apple Aperture all use algorithms specifically designed to simulate the effects of exposure adjustment within the camera. They are calibrated in stops rather than arbitrary numbers, and are fairly accurate, although their effects will vary widely between applications. They are arguably the best means of adjusting exposure.
Sunday, December 18, 2011
Selecting, Rating and Tagging Images
The first step of the post-processing workflow is to select the images you wish to keep, and to tag those that require further processing. This allows you to discard any outtakes or mishaps that take up valuable space on your workstation’s hard disk. You perform this task using Adobe Bridge, or the library viewer of other applications such as Aperture or Lightroom.
First, create a folder on your workstation or in your applications’s library to contain all the images offloaded from cameras and/or flash memory cards. Mine is named “Contact Sheet”, and contains subfolders for each of my cameras, even my film bodies which hold 35mm film scans.
As you add images to these folders, you review them from time to time and eliminate any completely wrong exposures, such as those first few images shot on the settings used from the previous session. Don’t actually delete them but “reject” them (tag them as “rejected”) if your application allows. This hides them from view, but allows them to remain in the folder. This way, if you to select and import all the images from the SD card (or other flash memory), to this folder, the application will “see” any duplicates and give you the opportunity to skip them. This ensures that you don’t leave any images behind. Once the card is reformatted, you can then delete the rejects.
Now comes the time to review the images. Rate any obvious keepers with five stars, workable images with three, and dogs with one, basing these decisions mostly on composition. Is the scale adequate? Are background elements interfering with the readability of the subject? Is it reasonably in focus?
Then, revisit these images and look at fine details such as focus and shadow/highlight detail. If two images are rated three, but on closer inspection one of them is sharper, upgrade it to a four. Of those fives, there may be some softer ones, so downgrade those to a four. The ones may be technically inferior, but they may have artistic potential, so uprate them accordingly. The background may be completely blown out, and the foreground way too dark, but this might make for an expressive silhouette.
Once you arrive at a final set of images, you can then tag them further with “keywords”, which will allow you to find them more easily in the future. You can now also tag them for further post-processing.
When the time comes to archive the images, this tagging process will enable you to quickly select and move them to their respective archive folders for burning onto optical media. The images tagged for further processing can then be moved to a separate folder until they are complete. Mine is named, “Lightbox”.
Dust and scratch removal often take a long time, distributed over several “sessions”. The working images (in “lossless” TIFF format so that subsequent savings don’t degrade image quality) remain in the Lightbox folder until they are complete, when they are saved as final JPEG copies. Aperture, Camera Raw, and Lightroom allow you to clone out spots in JPEG files using non-destructive algorithms, so you can leave them in this format to save space if you wish. Once complete you make a single duplicate JPEG copy with the changes in place, minimizing any image degradation.
Thursday, September 29, 2011
The Photo Library
Your “Photo Library” is your permanent collection of photographic works from various sources. You’ll want to differentiate these images from your “Working” images, those images that are in a kind of “limbo”, awaiting rating, sorting and/or further processing. They may be stored in a special folder, or on a special volume, or even on a series of optical disks or other media.
As you begin building your photo library, you’ll want to incorporate some structure and guidelines to assure that things will be easy to find.
Separate your work from the work of others.
As you collect images, you’ll undoubtedly acquire photos from friends and family, images that you have downloaded from the internet, images you may have manipulated, etc. Building an image reference library is one of the greatest advantages of the internet. You can easily download images (with the permission of their owners, of course) but you wouldn’t want them to get mixed up with your images. For example, you may have the right to download the image for reference (Actually, all the images you browse are downloaded temporarily into you image cache folder, whether you have the owner’s permission or not) but you may not have permission to post it to your blog. So the first level of organization should be by usage rights. Possible categories might include:
Organize images into broad, logical categories.
Avoid having too many subfolders. It can make it difficult to spot duplicates and to find images in general. Instead of using a subfolder, use keywords to differentiate images within broad categories. These categories will vary widely depending on the type of work you do. As a consumer, you might organize images by date or by event. As an amateur, you might develop categories for the genres of images you take, such as portraits, landscapes, and still lifes. As a professional, you might use folders name by client and job number. And it’s very possible you might use all three systems.
For example:
Back up your images regularly.
Employ a separate drive and use back software, not the file copy function in your operating system. Backup software copies only modified versions, saving time and wear and tear on your backup hard drive. It can also preserve previous versions, so if you made a change last week, you can still recover the previous version from last month. And if you’ve accidentally deleted image files from the folders that are being backed up, they’ll still be there in you backup.
Archive your images to optical disk and catalog them.
No matter how large your hard disk, it will eventually fill up. And the greater your “online” storage space, the larger your backup volume will need to be. The solution is to archive your images to removable media and catalog them for easy retrieval. At the present time, the optical disk (Recordable or re-writable CD or DVD) is the most cost-effective, compatible and durable media.
Previously, re-writable MO disks and tape were used, but these were slow to record, and in the case of tape, even slower to retrieve. They also required special hardware. Recordable DVD and CD media are recognized by practically ever computer, and to a somewhat lesser extent, rewritable media as well. Flash memory is by far the most convenient, but it’s also prone to degradation, so it’s not a wise choice for long-term storage. Rewritable optical disk is also more prone to failure. But write-once disks are quite stable, and quite inexpensive.
A good rule to follow is once a category folder reaches the capacity of the volume you plan to archive to (4.6 GB for a single-layer DVD for example), archive its contents to optical disk and catalog it with a disk cataloging application. Store these catalogs on your hard drive for easy retrieval.
Develop logical, unique names for image files and volumes.
Naming volumes sequentially does not guarantee that duplicates won’t happen, but naming them chronologically does. For example, naming archive volumes “DVD20100531” and “DVD20110823” ensures that they’ll each have a unique name, they’ll be sorted chronologically, you’ll know what media you used, and you’ll know when they were archived. Plus, there’s no need to look to see what the last volume name was.
Different cameras use different naming conventions. You can use them as is, or you can develop your own. But whichever method you choose, make sure that each image’s name is unique. If you create a variation of an image, keep the same image number but append it with a version number. One of the reasons for this is that you can save the Camera Raw settings for a specific image as an .xmp file with the same name as the image, rather than save a second copy of the file itself. If the .xmp settings and the image file become separated, you can then re-import them.
Prepare images beforehand for archiving.
Because you’ll likely be archiving to JPEG, which is a lossy format, you’ll want to make sure your images are in a good state prior to the compression process employed in saving to the JPEG format. This means removing dust and scratches and cleaning up the image in general. However, it’s wise to avoid over-processing the image. If the image requires a white balance adjustment, that’s fine. But sharpening the image is a no-no. The additional contrast between adjacent pixels will actually increase the file size, and there may be better sharpening algorithms in the future.
Don’t be afraid to leave yourself notes.
Life is busy. It’s easy to forget the “standard operating procedures” you have established. Creating “readme” files directly in your folders, like those that often come with your operating system, will help to ensure consistency.
As you begin building your photo library, you’ll want to incorporate some structure and guidelines to assure that things will be easy to find.
Separate your work from the work of others.
As you collect images, you’ll undoubtedly acquire photos from friends and family, images that you have downloaded from the internet, images you may have manipulated, etc. Building an image reference library is one of the greatest advantages of the internet. You can easily download images (with the permission of their owners, of course) but you wouldn’t want them to get mixed up with your images. For example, you may have the right to download the image for reference (Actually, all the images you browse are downloaded temporarily into you image cache folder, whether you have the owner’s permission or not) but you may not have permission to post it to your blog. So the first level of organization should be by usage rights. Possible categories might include:
- Client Work
- Downloads
- My Work
- Stock Photography
Organize images into broad, logical categories.
Avoid having too many subfolders. It can make it difficult to spot duplicates and to find images in general. Instead of using a subfolder, use keywords to differentiate images within broad categories. These categories will vary widely depending on the type of work you do. As a consumer, you might organize images by date or by event. As an amateur, you might develop categories for the genres of images you take, such as portraits, landscapes, and still lifes. As a professional, you might use folders name by client and job number. And it’s very possible you might use all three systems.
For example:
- Client Work
- Braunschweiger
- New York Times
- Pirelli Tires
- Starbucks Coffee
- Time Inc.
- Vogue Magazine
- Downloads
- Cameras
- Celebrities
- Works
- My Work
- Abstract
- Landscapes
- Portraits
- Still Life
- Street
- Stock Photography
- Corbis
- Getty Images
- iStock Photo
Back up your images regularly.
Employ a separate drive and use back software, not the file copy function in your operating system. Backup software copies only modified versions, saving time and wear and tear on your backup hard drive. It can also preserve previous versions, so if you made a change last week, you can still recover the previous version from last month. And if you’ve accidentally deleted image files from the folders that are being backed up, they’ll still be there in you backup.
Archive your images to optical disk and catalog them.
No matter how large your hard disk, it will eventually fill up. And the greater your “online” storage space, the larger your backup volume will need to be. The solution is to archive your images to removable media and catalog them for easy retrieval. At the present time, the optical disk (Recordable or re-writable CD or DVD) is the most cost-effective, compatible and durable media.
Previously, re-writable MO disks and tape were used, but these were slow to record, and in the case of tape, even slower to retrieve. They also required special hardware. Recordable DVD and CD media are recognized by practically ever computer, and to a somewhat lesser extent, rewritable media as well. Flash memory is by far the most convenient, but it’s also prone to degradation, so it’s not a wise choice for long-term storage. Rewritable optical disk is also more prone to failure. But write-once disks are quite stable, and quite inexpensive.
A good rule to follow is once a category folder reaches the capacity of the volume you plan to archive to (4.6 GB for a single-layer DVD for example), archive its contents to optical disk and catalog it with a disk cataloging application. Store these catalogs on your hard drive for easy retrieval.
Develop logical, unique names for image files and volumes.
Naming volumes sequentially does not guarantee that duplicates won’t happen, but naming them chronologically does. For example, naming archive volumes “DVD20100531” and “DVD20110823” ensures that they’ll each have a unique name, they’ll be sorted chronologically, you’ll know what media you used, and you’ll know when they were archived. Plus, there’s no need to look to see what the last volume name was.
Different cameras use different naming conventions. You can use them as is, or you can develop your own. But whichever method you choose, make sure that each image’s name is unique. If you create a variation of an image, keep the same image number but append it with a version number. One of the reasons for this is that you can save the Camera Raw settings for a specific image as an .xmp file with the same name as the image, rather than save a second copy of the file itself. If the .xmp settings and the image file become separated, you can then re-import them.
Prepare images beforehand for archiving.
Because you’ll likely be archiving to JPEG, which is a lossy format, you’ll want to make sure your images are in a good state prior to the compression process employed in saving to the JPEG format. This means removing dust and scratches and cleaning up the image in general. However, it’s wise to avoid over-processing the image. If the image requires a white balance adjustment, that’s fine. But sharpening the image is a no-no. The additional contrast between adjacent pixels will actually increase the file size, and there may be better sharpening algorithms in the future.
Don’t be afraid to leave yourself notes.
Life is busy. It’s easy to forget the “standard operating procedures” you have established. Creating “readme” files directly in your folders, like those that often come with your operating system, will help to ensure consistency.
Sunday, September 18, 2011
The JPEG Workflow
With the ability to store adjustments as metadata without un-compressing, modifying and re-compressing lossy JPEG data, The JPEG workflow has become one of the most popular.
Using Adobe Camera Raw, Adobe Lightroom, Apple Aperture and others, you can perform sophisticated adjustments to your JPEG images and store them within a database, or as sidecar XMP files attached to the images. The capabilities of these applications are so robust that unless you need to work in alternative color spaces such as L*a*b*, or need to modify the pixels themselves for combining images or extensive retouching, they will more than likely meet your post-processing needs.
Unlike Photoshop, which requires you to know the effects of each of its sophisticated tools, the ACR interface features sliders which address each issue; white balance, exposure, recovery, fill light, black level, brightness, contrast, clarity, vibrance, and saturation. And that’s only in the first of eight panels!
For example, to adjust exposure image in Photoshop, you could use Brightness/Contrast, Levels, Curves, Exposure, Multiply, or Screen. And some functions, like White Balance, are simply not available in Photoshop. With ACR and Apertture, it’s simply a matter of adjusting the sliders until the image’s exposure, color and contrast characteristics fall into place.
Through the use of Smart Objects, you can open an image adjusted in ACR as an editable layer within the Photoshop document. Double-clicking on this layer will open the ACR interface and allow you to fine-tune adjustments, which will then update any subsequently applied Photoshop adjustments.
Aperture by Apple allows you to treat a series of images as a single project, and store them in a self-contained file for easy archiving. It combines the functions of Adobe Camera Raw and Bridge into a single application for complete image project management.
Using Adobe Camera Raw, Adobe Lightroom, Apple Aperture and others, you can perform sophisticated adjustments to your JPEG images and store them within a database, or as sidecar XMP files attached to the images. The capabilities of these applications are so robust that unless you need to work in alternative color spaces such as L*a*b*, or need to modify the pixels themselves for combining images or extensive retouching, they will more than likely meet your post-processing needs.
Unlike Photoshop, which requires you to know the effects of each of its sophisticated tools, the ACR interface features sliders which address each issue; white balance, exposure, recovery, fill light, black level, brightness, contrast, clarity, vibrance, and saturation. And that’s only in the first of eight panels!
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Adobe Camera Raw Interface
Multiple image files can be opened at once, and appear in the pane to the left. File browsing is accomplished using the standalone application Adobe Bridge. ACR behaves as a preliminary step to opening the image files in Photoshop. Adjustment parameters are fixed and arranged in a non-scrolling pane to the right under eight separate tabbed panels
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For example, to adjust exposure image in Photoshop, you could use Brightness/Contrast, Levels, Curves, Exposure, Multiply, or Screen. And some functions, like White Balance, are simply not available in Photoshop. With ACR and Apertture, it’s simply a matter of adjusting the sliders until the image’s exposure, color and contrast characteristics fall into place.
Through the use of Smart Objects, you can open an image adjusted in ACR as an editable layer within the Photoshop document. Double-clicking on this layer will open the ACR interface and allow you to fine-tune adjustments, which will then update any subsequently applied Photoshop adjustments.
Aperture by Apple allows you to treat a series of images as a single project, and store them in a self-contained file for easy archiving. It combines the functions of Adobe Camera Raw and Bridge into a single application for complete image project management.
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| Apple Aperture 3 Interface
Files are imported into the Aperture library, which does include its own file brower. Files can be stored within the library, or remain in their original location. Adjustment parameters can be added, removed, enabled and disabled at will and reside in a single scrolling pane to the left. These include, Retouch, Red Eye Correction, Spot & Patch, Straighten, Crop, Flip, Chromatic Aberration, Devignette, Noise Reduction, White Balance, Exposure, Enhance, Curve, Highlights & Shadows, Levels, Color, Black and White, Color Monochrome, Sepia Tone, Sharpen, Edge Sharpen, and Vignette.
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| Capture One Interface
The folder structure can be browsed in real time as in Adobe Bridge. The Adjustment parameters are fixed and reside in a pane to the left under six tabbed panels.
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Wednesday, September 14, 2011
The Workflow
Whether you’re a casual snapshooter, an aspiring amateur or a busy professional, you’ll need to develop a workflow to process and store your images.
Tuesday, September 13, 2011
Retouching vs. Post-Processing
Retouching is a broad term used to describe the practice of preparing images for printing, traditionally known as prepress. It encompasses color correction, blemish removal, the combining of images and just about anything else that can be done to manipulate photographs to the client’s satisfaction in a way that will meet press requirements.
However, the term “prepress” is quickly becoming obsolete, replaced by the term “premedia”, and likewise the term “retouching” is being replaced by the term “Post-Processing”.
Just like film images, all digital images require processing. Most of the time, this is performed by the camera as the image is saved to flash memory. However, processing can also be performed outside of the camera in a “lightroom”, the digital equivalent to the traditional darkroom. And even if the image has been processed by the camera, additional processing can be applied to further enhance it.
In the past, chromes, negatives and even prints would be manipulated with dyes and bleach and adjusted using filters to arrive at a final photographic print. This print would then be photographed with a process camera in order to create four-color separations for printing. Subsequent retouching could then be performed through dot etching. With the advent of the drum scanner, 32-bit digital scanning replaced the process camera, producing CMYK separations directly from film or prints that could be adjusted through computer software.
Until recently, all of these operations have existed in the “prepress” domain. With the advent of the digital camera, digital image manipulation has begun to break free from this paradigm.
With the post-processing capabilities afforded by the digital medium, one seems almost compelled to manipulate images digitally. As a result, many of the creative and lighting decisions that were traditionally made behind the camera are now deferred to the digital lightroom. This revellation has made post-processing a very real part of Photography in the digital age.
Post-processing can also be seen as the natural progression of printing. Much of the art behind traditional photography was performed in the darkroom during the printing process. Dodging and burning were used to extend the dynamic range of the image, and alternate papers, chemistry and filters used to control contrast and color. Today, these processes are all all handled in the lightroom.
However, the term “prepress” is quickly becoming obsolete, replaced by the term “premedia”, and likewise the term “retouching” is being replaced by the term “Post-Processing”.
Just like film images, all digital images require processing. Most of the time, this is performed by the camera as the image is saved to flash memory. However, processing can also be performed outside of the camera in a “lightroom”, the digital equivalent to the traditional darkroom. And even if the image has been processed by the camera, additional processing can be applied to further enhance it.
In the past, chromes, negatives and even prints would be manipulated with dyes and bleach and adjusted using filters to arrive at a final photographic print. This print would then be photographed with a process camera in order to create four-color separations for printing. Subsequent retouching could then be performed through dot etching. With the advent of the drum scanner, 32-bit digital scanning replaced the process camera, producing CMYK separations directly from film or prints that could be adjusted through computer software.
Until recently, all of these operations have existed in the “prepress” domain. With the advent of the digital camera, digital image manipulation has begun to break free from this paradigm.
With the post-processing capabilities afforded by the digital medium, one seems almost compelled to manipulate images digitally. As a result, many of the creative and lighting decisions that were traditionally made behind the camera are now deferred to the digital lightroom. This revellation has made post-processing a very real part of Photography in the digital age.
Post-processing can also be seen as the natural progression of printing. Much of the art behind traditional photography was performed in the darkroom during the printing process. Dodging and burning were used to extend the dynamic range of the image, and alternate papers, chemistry and filters used to control contrast and color. Today, these processes are all all handled in the lightroom.
Tuesday, September 14, 2010
Color Management
In the world of professional imaging, known in these hi-tech times as premedia, color management is king. And, as a consumer, amateur or professional photographer, it’s equally important for you to know your way around this subject in order to achieve the level of quality you are expecting.
Color management, simply put, is the ability to adapt different capture devices with different color characteristics to different output devices, also with different color characteristics. This is achieved through ICC color profiles, data which tells the device how the color actually looks, and how to make it look the way it should.
It works this way; your camera captures and stores images, which exist in the natural color space of the camera, determined by its sensor and imaging engine. But your computer, and the application you plan on using to view or post-process your images, know nothing of these characteristics. So, when you import the images from your camera the computer doesn’t now how to make them look. So, they all have a color cast (let’s say blue), and they’re all a bit flat (have low contrast). Enter color management.
Most cameras export images to a standard color space, which can be interpreted by the computer. So, the job of the profile is to apply a curve that counteracts the blue cast, and restores the correct level of contrast. Use the correct profile, and the image looks as it should. Use the incorrect profile, and things begin to go horribly wrong. Use no profile, and you take your chances either way.
The Input Color Space
So, which profile should you be using? Naturally, there isn’t a straightforward answer to this question. But for now, let’s just say that practically all modern consumer capture devices (which includes not only cameras but scanners as well) export the images to the sRGB color space. sRGB IEC61966-2.1 to be exact. So, it’s likely that you’re already using this color space. No problem there.
The problem comes comes when you import the images to your computer, but it does’t know that they’re the the sRGB color space because the images were not tagged as such. And I’ll pass along a little story to explain this.
A few years ago, I had a color management epidemic, whereby most of the color was being kicked back by our clients for the same reason; the skintones were far too red, and the shadow detail far too dark. As it turned out, clients were supplying us with digital images which were untagged, meaning information regarding in which color space the image was exported was not included in the image file. So, when the images were first opened, Photoshop asked that an appropriate color profile be chosen. Naturally, having learned a little about digital color along the way, most of my colleagues chose Adobe RGB (1998), the superior color space.
A little knowledge can be a dangerous thing.
The fact is, Adobe RGB (1998) is a superior color space. It’s color gamut (the range of colors it can store) represents both what the eye can see, and what can be printed using the CMYK four-color process. Sadly, sRGB falls a little short. But, speaking English does’t help you when others understand only French. If you don’t speak the native tongue, you can’t interpret the information correctly.
The other, less common half of the epidemic was that the color was kicked back for being “flat and dirty”. Flat, meaning too little contrast, and dirty meaning that the fleshtones leaned toward cyan, the compliment of red. As it turned out, this is exactly what happens when you assign the wrong ICC color profile to an image.
So all this translated to two scenarios:
sRGB images which were not tagged sRGB were being interpreted in Adobe RGB (1998) color space, forcing them to gain contrast and shift to red.
Adobe RGB (1998) images (far less common) which were not tagged Adobe RGB (1998) were being interpreted in the sRGB color space, forcing them to lose contrast and shift toward cyan.
No one likes little green people, so even without the knowledge that Adobe RGB (1998) is a superior color space, folks tend to prefer the warmer look of Adobe ’98. That is, until it finds it’s way onto a contract proof.
The biggest problem in color management is the fact that you can easily assign a different profile to an image than the actual color space in which it exists, or, not assign one at all, leaving everyone guessing. And if the latter is the case, it takes a very experienced professional to know which is the correct profile to assign. Therefore, unless the image comes from a reliable source, never trust an embedded profile.
The Output Color Space
Incorrectly assigned profiles are easily corrected by simply assigning and embedding the correct profile, because assigning a profile (tagging an image file) is non-destructive (does not permanently affect image pixel values).
However, the real problem happens once the image is converted to another color space, such as the working space or the output space, which makes the interpreted color more or less permanent, or at the very least not easily undoable. So, you don’t want to archive your images in the output space, because it may change depending on the service provider or destination media. If the initial color space is interpreted correctly, you can freely convert from one color space to another, including L*a*b*, RGB’s close cousin.
Therefore, sRGB is the most common RGB output space, since it’s the native color space of computer displays, consumer photo printers, commercial photo printers, and the web, all of which are output destinations.
The other type of output profile would be for commercial printing, which most likely will be a CMYK output profile such U.S. Web Coated (SWOP) v2.
When an RGB image is converted to CMYK, it becomes a 48-bit image, each of the four channels containing 8 bits of grayscale information. The gray component of the three RGB additive primaries (colors which are neutral and dark) are removed from each of the RGB channels, and combined into the black channel. Each of these channels is then inverted to reflect the change from an additive (transmissive) color space to a subtractive (reflective) color space. The specifics of these conversions are very different depending on the press profile. Therefore, converting to a CMYK space is not reversible.
The Working Space
This is an intermediate color space that you use to work in, and the intended purpose for Adobe RGB 1998. The reason to convert to (NOT assign) a working space is to expand the color gamut to allow enough room for the enhancements you are likely to make during post-processing. For example, in the process of adding saturation, you’ll be changing the values of the existing pixels to brighter colors than can be stored in the sRGB space. Since the working space is the space you are going to archive your images in, you will always have all the information you’ll need for the best possible conversion to the output space, be it now or in the future.
Many new cameras include the ability to store images in the Adobe space, which works equally well as both a capture and working space. This has the advantage of simplifying workflow, since only one conversion to the output space is required.
One the other hand, if you do not intend on doing any post-processing or are planning on printing directly from your camera or memory card, sRGB is probably the best choice. Most commercial photo printers work with this color space exclusively, so if you hand them a card with Adobe 98 images, they'll come back red and contrasty.
ProPhoto is a color space designed with the professional photographer in mind. It’s large gamut is designed to store every concievable color from the widest variety of capture sources. It’s an excellent space in which to process and archive images, but conversion to an output space is an absolute must.
Color Gamut vs. Bit Depth
The other caveat to working space is bit depth, or the amount of tonal information stored in the original file. A standard “24-bit” RGB image file has 8 bits per channel for a total of 256 levels of tonality. A 48-bit CMYK image has the same number of levels, it just has an extra channel for black.
But a 16-bit file has 65,536 levels of gray. It is said that a print can only store about 100 levels. The question is, which 100 of the 65,536 will you choose? In other words. If you have a grossly underexposed digital image with 65,536 levels of information, lightening the image to fit those 100 on a paper print with no degradation of image quality is a snap.
The downside to a 16-bit working space is that it takes up a lot of space when archiving, so use it for only the most worthwhile images. Also, many Photoshop filters will not work with 16-bit images.
Summary
That’s a lot to digest, so here’s a quick summary for reference:
Use the sRGB color space when:
Capturing images that are to be printed directly from the camera or memory card.
Converting images for use on the web, or being handed off to a commercial photo printer.
Use the Adobe RGB (1998) color space when:
Capturing images that will be post-processed and archived with layers intact.
Converting images from sRGB that will be post-processed and archived with layers intact.
Use the ProPhoto RGB color space when:
Converting images from any capture color space that will be post-processed and archived with layers intact.
Use 16-bit color when:
Converting 12 or 14-bit Camera Raw images that will be heavily post-processed such as extreme exposure adjustments.
Working with high-quality grayscale images.
Converting images from any color space that will have gradients added to them in Photoshop.
Color management, simply put, is the ability to adapt different capture devices with different color characteristics to different output devices, also with different color characteristics. This is achieved through ICC color profiles, data which tells the device how the color actually looks, and how to make it look the way it should.
It works this way; your camera captures and stores images, which exist in the natural color space of the camera, determined by its sensor and imaging engine. But your computer, and the application you plan on using to view or post-process your images, know nothing of these characteristics. So, when you import the images from your camera the computer doesn’t now how to make them look. So, they all have a color cast (let’s say blue), and they’re all a bit flat (have low contrast). Enter color management.
Most cameras export images to a standard color space, which can be interpreted by the computer. So, the job of the profile is to apply a curve that counteracts the blue cast, and restores the correct level of contrast. Use the correct profile, and the image looks as it should. Use the incorrect profile, and things begin to go horribly wrong. Use no profile, and you take your chances either way.
The Input Color Space
So, which profile should you be using? Naturally, there isn’t a straightforward answer to this question. But for now, let’s just say that practically all modern consumer capture devices (which includes not only cameras but scanners as well) export the images to the sRGB color space. sRGB IEC61966-2.1 to be exact. So, it’s likely that you’re already using this color space. No problem there.
The problem comes comes when you import the images to your computer, but it does’t know that they’re the the sRGB color space because the images were not tagged as such. And I’ll pass along a little story to explain this.
A few years ago, I had a color management epidemic, whereby most of the color was being kicked back by our clients for the same reason; the skintones were far too red, and the shadow detail far too dark. As it turned out, clients were supplying us with digital images which were untagged, meaning information regarding in which color space the image was exported was not included in the image file. So, when the images were first opened, Photoshop asked that an appropriate color profile be chosen. Naturally, having learned a little about digital color along the way, most of my colleagues chose Adobe RGB (1998), the superior color space.
A little knowledge can be a dangerous thing.
The fact is, Adobe RGB (1998) is a superior color space. It’s color gamut (the range of colors it can store) represents both what the eye can see, and what can be printed using the CMYK four-color process. Sadly, sRGB falls a little short. But, speaking English does’t help you when others understand only French. If you don’t speak the native tongue, you can’t interpret the information correctly.
The other, less common half of the epidemic was that the color was kicked back for being “flat and dirty”. Flat, meaning too little contrast, and dirty meaning that the fleshtones leaned toward cyan, the compliment of red. As it turned out, this is exactly what happens when you assign the wrong ICC color profile to an image.
So all this translated to two scenarios:
sRGB images which were not tagged sRGB were being interpreted in Adobe RGB (1998) color space, forcing them to gain contrast and shift to red.
Adobe RGB (1998) images (far less common) which were not tagged Adobe RGB (1998) were being interpreted in the sRGB color space, forcing them to lose contrast and shift toward cyan.
No one likes little green people, so even without the knowledge that Adobe RGB (1998) is a superior color space, folks tend to prefer the warmer look of Adobe ’98. That is, until it finds it’s way onto a contract proof.
The biggest problem in color management is the fact that you can easily assign a different profile to an image than the actual color space in which it exists, or, not assign one at all, leaving everyone guessing. And if the latter is the case, it takes a very experienced professional to know which is the correct profile to assign. Therefore, unless the image comes from a reliable source, never trust an embedded profile.
The Output Color Space
Incorrectly assigned profiles are easily corrected by simply assigning and embedding the correct profile, because assigning a profile (tagging an image file) is non-destructive (does not permanently affect image pixel values).
However, the real problem happens once the image is converted to another color space, such as the working space or the output space, which makes the interpreted color more or less permanent, or at the very least not easily undoable. So, you don’t want to archive your images in the output space, because it may change depending on the service provider or destination media. If the initial color space is interpreted correctly, you can freely convert from one color space to another, including L*a*b*, RGB’s close cousin.
Therefore, sRGB is the most common RGB output space, since it’s the native color space of computer displays, consumer photo printers, commercial photo printers, and the web, all of which are output destinations.
The other type of output profile would be for commercial printing, which most likely will be a CMYK output profile such U.S. Web Coated (SWOP) v2.
When an RGB image is converted to CMYK, it becomes a 48-bit image, each of the four channels containing 8 bits of grayscale information. The gray component of the three RGB additive primaries (colors which are neutral and dark) are removed from each of the RGB channels, and combined into the black channel. Each of these channels is then inverted to reflect the change from an additive (transmissive) color space to a subtractive (reflective) color space. The specifics of these conversions are very different depending on the press profile. Therefore, converting to a CMYK space is not reversible.
The Working Space
This is an intermediate color space that you use to work in, and the intended purpose for Adobe RGB 1998. The reason to convert to (NOT assign) a working space is to expand the color gamut to allow enough room for the enhancements you are likely to make during post-processing. For example, in the process of adding saturation, you’ll be changing the values of the existing pixels to brighter colors than can be stored in the sRGB space. Since the working space is the space you are going to archive your images in, you will always have all the information you’ll need for the best possible conversion to the output space, be it now or in the future.
Many new cameras include the ability to store images in the Adobe space, which works equally well as both a capture and working space. This has the advantage of simplifying workflow, since only one conversion to the output space is required.
One the other hand, if you do not intend on doing any post-processing or are planning on printing directly from your camera or memory card, sRGB is probably the best choice. Most commercial photo printers work with this color space exclusively, so if you hand them a card with Adobe 98 images, they'll come back red and contrasty.
ProPhoto is a color space designed with the professional photographer in mind. It’s large gamut is designed to store every concievable color from the widest variety of capture sources. It’s an excellent space in which to process and archive images, but conversion to an output space is an absolute must.
Color Gamut vs. Bit Depth
The other caveat to working space is bit depth, or the amount of tonal information stored in the original file. A standard “24-bit” RGB image file has 8 bits per channel for a total of 256 levels of tonality. A 48-bit CMYK image has the same number of levels, it just has an extra channel for black.
But a 16-bit file has 65,536 levels of gray. It is said that a print can only store about 100 levels. The question is, which 100 of the 65,536 will you choose? In other words. If you have a grossly underexposed digital image with 65,536 levels of information, lightening the image to fit those 100 on a paper print with no degradation of image quality is a snap.
The downside to a 16-bit working space is that it takes up a lot of space when archiving, so use it for only the most worthwhile images. Also, many Photoshop filters will not work with 16-bit images.
Summary
That’s a lot to digest, so here’s a quick summary for reference:
Use the sRGB color space when:
Capturing images that are to be printed directly from the camera or memory card.
Converting images for use on the web, or being handed off to a commercial photo printer.
Use the Adobe RGB (1998) color space when:
Capturing images that will be post-processed and archived with layers intact.
Converting images from sRGB that will be post-processed and archived with layers intact.
Use the ProPhoto RGB color space when:
Converting images from any capture color space that will be post-processed and archived with layers intact.
Converting 12 or 14-bit Camera Raw images that will be heavily post-processed such as extreme exposure adjustments.
Working with high-quality grayscale images.
Converting images from any color space that will have gradients added to them in Photoshop.
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