by Dave Montizambert Published 01/02/2010
Lens Trick - Dave Montizambert
"...distance, not lens length, affects perspective..."
Here's a lens trick, based on a simple but often overlooked principle, that you can add to your bag of tricks: create a long lens compressed look with a short lens.
In photo one of model, Michelle Snow, I used a 105mm lens at a distance of 15 feet. With this lens at this distance Michelle fills the frame nicely, however, the background power-line poles look small and far away, adding little impact to the image. On photo two I swapped out the 105mm lens for a 300mm lens, then backed 42 feet away from Michelle to make her fill the frame appropriately. I think you will agree, this second image is much more interesting, notice the compression; the size relationship between Michelle and the background has evened out somewhat making the poles appear closer and more dramatic. Let me pose a question: is this cool compression because I used a 300 mm lens or is it because I walked 42 feet away from Michelle? Let's see if my third version of the image answers the question. In photo three I took the same picture again still at 42 feet but this time using the 105 mm lens. With this third image and the 300 mm image (for reference) open and tiled side by side in Photoshop, the crop tool was selected to crop in on the 105 mm lens at 42 feet image. The crop tool was set to match the framing and resolution of the 300 mm image. Notice that the perspective compression is identical in both shots. The underlying principle of this compressed look is - distance, not lens length, affects perspective. As you move away from a subject, nearer objects grow smaller at a faster rate than do further objects. As you move toward a subject, the nearer objects grow larger at a faster rate than further objects. But don't take my word for it, to see for yourself try this: with one eye closed view your hands held three inches away from your open eye. Back your left hand away so the distance between your two hands is about 8 inches. Observe the size difference between the two hands. Now, keeping the distance between the two hands constant, move them as far away as you can. Again observe the size relationship. At the close distance your right hand appears huge compared to the further left hand, and at far distance the right hand only appears slightly larger, that's perspective at work. So choose camera distance for the 'perspective look' you desire, then choose the correct lens to fill the frame appropriately or if you don't have that lens, then rely on the cropping features in Lightroom (LR), Adobe Camera Raw (ACR), or Photoshop to crop in on your image. I like to change my mind a lot, for this reason I prefer to use the cropping features in Lightroom and ACR rather than cropping in Photoshop. Cropping in LR or ACR only records the cropping coordinates and only applies them to the file rendered from the RAW file, at any time I can go back and re-edit my cropping. With Photoshop once you save and close the cropped file that is it, those cropped pixels have all gone to pixel heaven.
This 'lens trick' is a great solution in a pinch and technically the only difference between the two images is depth of field and image quality. Both images were shot at f2.8 but the size of Michelle in the 105 mm version of the image is smaller in camera than was Michelle in the 300 mm version, or at least until I cropped it. The underlying principle at work here is, depth of field increases when in camera subject size decreases; the more you reduce a subject's size from their actual size, the more depth of field you will get. As for image quality, the cropped image is made from fewer pixels, making it less resolved.
Dave Montizambert lectures internationally on lighting, digital photography and Adobe Photoshop. He is also a published author having written two books on lighting and digital photography (publisher Amherst Media) plus numerous magazine articles on these topics in North America and in Europe. Dave also creates Photoshop tutorial CDs & DVDs for www.software-cinema.com.
Dave is available for lectures and workshops in your area and can be reached at montizambert@telus.
net or www.montizambert.com.
If you would like to learn more about digital lighting, check out Dave's book, Creative Lighting Techniques, available through Amherst Media and the SWPP bookstore.
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