Does a crop sensor change lens distortion or portrait perspective?
Asked 8/22/2012
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I’ve seen videos saying shorter focal lengths can make portraits look less flattering because of “distortion.” If I use the same lens on a Canon APS-C body with a 1.6x crop factor, does that distortion change?
My understanding is that a crop sensor is like taking the same image and cropping the center, so the image itself doesn’t change—just the field of view. But since many optical distortions are stronger near the edges of the frame, does using a smaller sensor reduce the visible distortion? And for portraits, does a crop sensor change the perspective effect people often attribute to wide-angle lenses?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
14y ago
2 Answers
8
Does sensor size affect lens distortion?
Short answer: Yes.
The reason is only because most if not all distortion happens on the edges of the lens glass. Using a cropped sensor is indeed
like printing off a 8x10 picture and then cutting out the 4x6.
and therefore by trimming the edges you will most likely get rid of some of the distortion.
Just to rectify/precise Stan's statement:
What changes is perspective.
The size of the sensor does not change the perspective. The perspective is only affected by the distance between the lens and the subject no matter its focal length.
As a matter of a fact should one take an exposure with a 200mm lens and then from the same location take the same exposure with a 20mm lens the perspective will be the same. What changes is the amount of information you will see in the 2 exposures. Crop the 20mm lens exposure to match the same field of view of the 200mm lens and you will see the perspectives are identical. The same logic goes for cropped sensor. a 50mm lens on a cropped sensor might have a FOV of a 75mm lens on a full frame body but the perspective remains unchanged nonetheless.
Originally by user14048. Source · Licensed CC BY-SA 4.0
user14048
13y ago
0
Generated from our catalog & community — verify before relying on it.
A crop sensor does not change the lens’s actual optical behavior or perspective by itself. It just records a smaller central portion of the image circle, like cropping the full-frame image.
That means two different things:
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Optical distortion: if a lens has barrel/pincushion distortion that is stronger toward the edges, a crop sensor may show less of it simply because it uses less of the outer image area.
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Portrait “distortion”: the unflattering look from wide-angle portraits is mostly perspective distortion, not lens distortion. Perspective depends on camera-to-subject distance, not sensor size. If you keep the camera in the same place and use the same lens, perspective stays the same on full frame and crop; the crop body just gives a narrower field of view.
In practice, people often stand farther back with a crop sensor to frame the same portrait, and that greater distance changes perspective in a more flattering way. So: crop sensors can reduce visible edge distortion, but they do not inherently change perspective—your shooting distance does.
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