How should I fairly compare detail between smartphone cameras with different focal lengths?
Asked 5/20/2026
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I want to compare image detail/resolution between two smartphones, one with a 23mm-equivalent main camera and one with a 35mm-equivalent camera. What is the fairest way to test detail when the focal lengths are different: should I change shooting distance so both phones frame the same field of view, or keep the same shooting distance and accept different framing? I'm specifically trying to compare captured detail rather than brightness.
Originally by Landon Ham. Source · Licensed CC BY-SA 4.0
Landon Ham
22d ago
2 Answers
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Detail (resolution) and the amount of reflected light recorded are not directly related. And focal length (subject distance) is not the sole determination of the amount of light recorded.
I.e. In terms of detail one lens could simply be sharper/better quality. In terms of light the 23mm lens could be an f/5.6 and the 35mm could be an f/4... the f/4 would transmit twice as much light.
In general, if the recorded FOV is the same, the amount of light recorded is the same. If the FOV is different, the amount of light (from the subject) is different, but the exposure is still the same. (all else being equal). E.g. if a lightbulb is recorded smaller (from farther or with a shorter FL) the amount of light received from it is also less, but that light is concentrated into a smaller area on the image plane; and therefore the exposure of the light bulb remains constant.
Originally by Steven Kersting. Source · Licensed CC BY-SA 4.0
Steven Kersting
22d ago
0
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For a fair detail comparison, match the framing/field of view. In practice, move the phones to different distances so the subject appears the same size in both images, then compare the same area at the same output size or crop. Keeping the same distance but using different focal lengths changes magnification and framing, so you’re no longer comparing detail under equivalent conditions.
Also, detail and light are not the same thing. Resolution depends on factors like lens sharpness, sensor resolution, processing, and focus accuracy. Light gathered depends on exposure settings and aperture, not just focal length or distance. Two cameras can have different focal lengths yet record the same exposure for the same scene.
So: if your goal is perceived detail on the subject, equalize the composition first. Then compare sharpness/fine texture in matched crops under the same lighting and exposure conditions.
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