On Taking Perspective...

Nikon PC-E Micro NIKKOR 45mm f/2.8D Perspective Control Lens

Along with catadioptric (mirror) lenses, I’ve always been intrigued with the “perspective control” lens, also known as a “tilt and shift” lens. It’s the SLR’s take on the view camera, bringing some of its functionality to the smaller 135 format. One of its many uses is to correct the rather odd perspective when photographing tall buildings or other objects from a low angle. It’s what separates the pros from the amateurs in dedicated architectural photography.


This particular lens runs a little over $2,000, so it’s not a casual purchase. But if you plan on doing a lot of architectural work, it’s definitely a worthwhile one.

In the meantime, you can achieve a similar effect in Photoshop using the perspective transform function (Edit > Transform > Perspective. It does a fairly good job as you can see from the examples below:

Big Ben, as shot

Big Ben, perspective-corrected in Photoshop

Shifting the Lens

I didn’t try to take it all the way, I left a little bit of distortion there to add credibility. But I could have easily corrected it so both sides of the tower were perfectly parallel.

There are several approaches to doing this. You can expand the top outward, which saves you the trouble of re-cropping the image. Since this stretches out the image pixels, it reduces sharpness somewhat, and in pictures with visible grain, might look a little strange. It also tends to make the image look fatter overall.

Tilting the Lens

The other technique would be to pinch the bottom in, which preserves the resolution at the expense of requiring re-cropping. This makes the image look skinnier.

Finally, you could split the difference, expanding the top while pinching the bottom. You’ll still need to re-crop, but this option may give you the best of both worlds.

Photoshop can’t do it all, however. In addition to shifting, the perspective control lens can also tilt and rotate. You can use these additional movements to create areas of selective focus. This can lend a “miniaturized” look to your images, as if reality was recreated in a small scale model. Again, you can simulate this effect in photoshop, but it is just that...a simulation. And tricky...

London in Miniature: Big Ben

London in Miniature: Along the Thames

Not having a perspective control lens (yet?), I can’t show you examples of the real thing. But, these photoshop simulations should give you the idea. It’s not as easy as it seems to to achieve this effect, because:

1. Gaussian Blur, when applied on a layer using a gradient mask, varies the opacity of the layer, not the intensity of the blur effect itself. So, the out-of-focus areas take on a kind of glow near the 50% point.
   
   
2. Vertical surfaces at the plane of sharp focus must remain in focus, so applying a simple gradient mask is not enough. You must add these objects to the gradient mask.
   

So, once again, digital retouching can allow you to achieve the effects of more expensive equipment, if not necessarily the quality.

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Learn more about Nikon and Canon perspective control lenses. You can also view samples of photos taken with perspective control lenses.