Why can the same lens show different vignetting on different camera sensors?
Asked 5/6/2015
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I found test results for the Sony 16-50mm f/2.8 showing very different corner shading at 16mm f/2.8 depending on the camera body used. For example, one review measured about 0.75 EV on a 14 MP body, while others measured around 1.8–1.9 EV on 24 MP bodies.
Can sensor resolution itself increase measured vignetting, or are these differences more likely caused by sensor design? How can the same lens appear to vignette more on one camera than another?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
11y ago
2 Answers
5
This could be due to either the angular dependence of image pixels or the design (level of offsetting) in the microlenses.
If you imagine an image pixel as a bucket with the light sensitive part in the bottom, light coming from directly above will hit the bottom with no problems. However the more oblique the angle of light the less will hit the bottom as it is blocked by the sides. This is sort of how a pixel works in a front side illuminated sensor, there are wires and other structures in front of the actual photosensitive area.
If you have a higher resolution sensor then the pixels are smaller but have the same "depth", so if you imagine a bucket with the same height but smaller diameter, the angle over which light can hit the bottom is greatly reduced.
In order to try and mitigate this issue, digital camera sensors have microlenses which try to focus the incoming light onto the small photosenstive area within each pixel. Toward the edges of the sensor (where incoming light angles are naturally shallower, and where vignetting occurs) offset microlenses are sometimes employed to redirect light so that it enters the pixel at a steeper angle.
Originally by user1375. Source · Licensed CC BY-SA 4.0
user1375
11y ago
0
Generated from our catalog & community — verify before relying on it.
Yes—measured vignetting can vary between camera bodies, but it is not simply because “more megapixels = more vignetting.” The bigger factor is sensor design.
Light reaching the corners of a wide-angle lens hits the sensor at a steeper angle than light in the center. On front-side illuminated sensors, each pixel is partly recessed beneath wiring and other structures, so oblique light is less efficiently captured. Smaller pixels on higher-resolution sensors can be more sensitive to this effect because the acceptable light angle is narrower.
Manufacturers reduce this with microlenses, including offset microlenses near the edges, but different sensors do this with different success. So the same lens can show different corner shading on different cameras.
Also, review sites may use different test methods, raw conversion, and correction settings, which can further change the reported EV numbers.
So: sensor resolution may correlate with stronger measured vignetting in some cases, but the real cause is pixel geometry, microlens design, and testing methodology—not resolution alone.
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