35MM vs 50MM perspective, which is best, were to see side by side examples.

Started Mar 18, 2013 | Questions thread
jrtrent Veteran Member • Posts: 4,279
Re: 35MM vs 50MM perspective, which is best, were to see side by side examples.

Camera to subject distance is what creates the manipulation of the depth portion of perspective in a photograph. A lens focal length does not create the perspective, and many people misunderstand this.

If you're talking about perspective as the size and distance relationships among a finite set of scene elements, such as a picket fence, a house, and a hill in the background, then changing the distance is the only way to change the perspective. You don't even need to change the focal length unless you want to fill each frame with about the same objects as you change your shooting position.

The perspective effect that I think Tamron and the DPReview blog are getting at is the fact that, under normal viewing conditions, wide angle lenses always give an exaggerated perspective while normal lenses render things more like what our eyes saw.

"At the simplest level, a standard lens is defined as one which produces images with a natural-looking perspective (the word 'normal' is often used synonymously in this context). This concept is perhaps best illustrated with regard to what it's not, that is to lenses which clearly don't meet this criterion. A telephoto lens, for example, renders distant objects larger in the frame, and has the effect of compressing the apparent spatial relationship between objects. A wideangle does precisely the opposite; in squeezing more content into the image, objects appear smaller and more distant. It's in the happy medium between these two extremes that the standard lens lies; the apparent sizes and spatial relationships between image elements appear natural, and much as they did in real life."

Another factor that gets brought up in this discussion is that even wide angle shots can look natural if viewed from the correct distance. An excerpt from one study on this effect said:

"Photographers, cinematographers, and computer-graphics engineers use certain techniques to create striking pictorial effects. By using lenses of different focal lengths, they can make a scene look compressed or expanded in depth . . . We asked why pictures taken with a certain focal length look natural, while those taken with other focal lengths look distorted. We found that people’s preferred viewing distance when looking at pictures leads them to view long-focal-length pictures from too near and short-focal-length pictures from too far. Perceptual distortions occur because people do not take their incorrect viewing distances into account. By following the rule of thumb of using a 50-mm lens, photographers greatly increase the odds of a viewer looking at a photograph from the correct distance, where the percept will be undistorted." http://www.emilyacooper.org/Emily_A._Cooper/Photographic_Practice_files/cooperpiazzabanks.pdf

The correct distance to view a print so that it will look normal, not compressed or expanded, they called the center of projection. This distance is calculated by multiplying the focal length of the lens by the magnification needed to attain the print size. What they found was that people tend to view a picture according to the size of the print rather than by the center of projection, and the distance most people viewed various size prints at turned out to be the center of projection distance for a 50mm lens (35mm format), hence their conclusion that using a normal 50mm lens greatly increases the chance that a viewer will look at the picture from a distance that renders an undistorted percept.

Since focal length is part of the formula for determining the distance for the center of projection, focal length has a direct influence on the perspective effect we see in the pictures.

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