The Truth About Filters…Confirmed.

Buying new lenses has meant having to buy new filters, since the lens I will be using most often has a different filter size from any I’ve had in the past. There seems to be a lot of myths and misconceptions regarding filters, so before investing any more money, I decided to do my homework before making any more purchases.

I’ve read dozens of articles stating that the only filters you need for digital cameras are neutral contrast (read “perfectly clear”) to protect your lens, polarizers, and neutral density. On the surface, this makes perfect sense. But I don’t completely buy it.

For starters, I don’t have to; since I’ll also be shooting film, I’ll need the usual complement of filters anyway. But the question remains which filters make the most sense for digital. At the very least, the answer will lead to wiser purchases.

When I say wiser, I mean most effective with least affect on image quality. The ultimate “digital” filter seems to not be a filter at all, but a high-quality coated piece of glass to protect your lens. Certainly the last thing I want to do is to put anything in front of my lens that will degrade the image, so here it’s either the best, or nothing. I could easily put on the lens hood that came with my camera, and save a hundred bucks. But that wouldn’t keep airbourne nasties from landing on my $700.00 lens.

On the other hand, I seem to have a problem spending all that money on something which only filters dust particles and not light particles. So, ye olde “UV” filter returns to the spotlight. Except that the local camera shop guy says you don’t need a UV filter with digital cameras, because the camera’s built-in filter takes care of that. Really. Well, my D90 has a superior infrared-blocking filter as well, and that doesn’t stop me from taking pretty good infrared photos with an R72 infrared pass filter which blocks nearly all visible light. So, I need more to go on.

Then, I come across a great article by Bob Atkins, “Filters - UV or not UV?” which spells it all out for me. He tests several popular filters at the time, and concludes that a handful work quite well, while others do virtually nothing. It occurs to me that if the camera’s UV filtering is as good as the camera shop guy says it is, then the only worthwhile purchase is the one that’s the most effective. So, I seek out Bob’s recommendations.

Sadly, one of them is no longer available, and instead I am shipped a new “Digital” version, carrying the designation UV(c) instead of UV(0), and not made in Japan. I am skeptical.

Ineffective Hoya UV filter. The “UV Protective Case” actually suppresses more UV than the filter does.

So, after reading several articles on UV photography (talk about going from one extreme to the other) it occurs to me that there’s a simple test I can do to confirm my suspicions. With a UV-only light source (the common “Black” light) and any object that fluoresces under that light source, I can test the effectiveness of any UV filter. Placing the filter between the black light and the fluorescent object, I can see without question how much UV light is blocked and how much is passed. And Bob Atkins research is spot-on, not that I doubted him for a minute; it’s just that he hasn’t tested every filter out there. But now I can.

This I can tell you. I have the UV(0) filter that Bob mentions in a 72mm size, and it is very effective in blocking UV. The new “Digital” UV(c) is virtually useless. Ironically, this filter comes in a UV-protected plastic case which is quite effective in suppressing UV. So, I’ll be returning this filter shortly, and never again will I settle for a UV filter that simply does not work.

So how does the black light test work? Well, if you look through the filter at the black light, you will notice no change. That’s because what you’re seeing is the visible part of the spectrum the black light is producing. What causes objects to fluoresce is the invisible part, or UV, which our eyes can’t see but the fluorescing object does. Blocking the UV stops the item from fluorescing, and you can tell the degree of suppression by the darkness of the circular shadow created by the filter.

I can now test other filters to see how they block UV light. Warming filters, such as the 81A and Skylight 1A also do a pretty good job of blocking UV, but unlike a UV filter, they alter the color temperature. The only essential color change with a UV filter is the removal of the blue cast caused by the UV light itself. But the real enhancement is in the sharpness and clarity of the image. I feel this makes a strong UV blocking filter (and not a skylight filter) ideal for a digital camera. And yes, I’ve also confirmed that it does make a difference in actual shooting. So take that, camera-shop guy.

I know, you’re looking for a recommendation, so here it is; two filters stand above the rest: The Hoya Pro1 Digital UV(0) MC, and the Tiffen Haze 2A.

The Hoya is multicoated (supposedly optimized for digital), and the Tiffen is not. The Tiffen is therefore less expensive, but is a superior UV blocker. Tiffen also makes a Haze-1 filter, which is not as strong as the Haze 2A, but possibly more effective than the Hoya. It’s your choice.

If you can find the older Hoya UV(0) filter, it too is just as effective as the new Pro1 Digital version. It’s unlikely you can purchase the multicoated version new (I’ve tried), but the single-coated version may still be available, and this would represent your best value. Beware of filters not made in Japan, because they may be newer, less effective replacements.

So, each one of my lenses will receive a Hoya Pro1 Digital UV(0) MC filter as a temperature-neutral, UV-filtering, Quality-preserving lens protector in its particular size.

All of my other filter purchases will be in the 67mm size, with step-up rings for my smaller lens sizes. I should still be able to use the bayonet hood included with the Nikkor 50mm f/1.4G with a 67mm filter. I can use the Hood on my Nikkor 16-85mm with a 72mm filter and step-up ring. Such is the design of the newer lenses and hoods. For lenses without hoods, I plan to use a 67mm screw-in hood.

Never again will I compromise on the quality of a filter, or settle for one that doesn’t do exactly what I expect it to.

Here are some other facts that may be of interest:

Film is inherently very sensitive to UV light, but not at all sensitive to Infrared. This is why you must use film specially sensitized for infrared to do infrared photography.

Digital cameras are inherently very sensitive to infrared, but less so to UV, hence the “Hot Mirror” filter. Their infrared sensitivity is so great, that it negatively affects visible light photography without this filter.

All lenses pass infrared light, “near” or “far”.

Only special lenses pass the “far” UV light required for UV photography. So, unless you can get your hands on a UV Nikkor 105mm lens, invest in an expensive “black” UV-pass filter, and modify your digital camera for UV, don’t go there.

Because lenses pass “near” UV light just beyond the visible spectrum, you need to use a UV filter when large amounts of it are present, such as high altitudes and near the ocean. At other times, as long as the quality of the glass and coatings are sufficient, the UV filter becomes a “clear” lens protector.

Not all polarizers are created equal, so never skimp on one. Better polarizers are more effective, pass more light, and are multicoated. However, avoid using them for landscapes with wide angle lenses (or with your zoom lens set to its widest angle.)

Polarizers are quite effective at suppressing UV light, so it's not necessary to use them with a UV filter. There are a number of UV/Polarizers available, but I would imagine there isn’t much of an advantage to them.

The two most important filters you can purchase for your digital camera are, in order:

1. An effective, neutral, multi-coated UV blocking filter which also doubles as a lens protector.
2. An effective, neutral, multi-coated Circular Polarizing filter to enhance contrast and saturation.

Some optical filters’ effects, such as but not limited to those of polarizers, UV, neutral density and infrared filters simply cannot be duplicated by either your camera or a post-processing application. Others such as red, orange, yellow and green filters used when capturing monochrome (black and white images) may yield better results than by using the camera’s software filters with the monochrome mode, or by shooting in color and optimizing the balance in post. Only you can tell through experimentation, but certainly these types of filter are truly optional for digital cameras.

It’s better to apply filters during shooting than in post-processing. For example, a top-quality warming filter would be a better choice than setting your camera’s white balance to the warm side. This in turn, would be a better choice than making a color correction in Photoshop. Anything you do in Photoshop is a compromise, but if you shoot JPEG, the degradation in resaving the image as a JPEG alone would make using a filter in the first place worthwhile.