Does crop factor change true macro magnification like 1:1?

Asked 2/17/2011

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If a lens or extension tube setup can reach 1:1 magnification, does using it on a 1.5× crop-sensor camera make it effectively 1.5:1? I'm asking whether crop factor changes the actual macro magnification, or only how tightly the subject is framed compared with full frame.

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

15y ago

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I'll just take this out into an actual answer, and the answer is 'NO', the crop factor doesn't make it a 1.5:1 ratio. What it does change is the ratio of information per pixel which would be an valid new designation.

Why? Because the 1:1 ratio is a designation of how large the lens renders subjects on the focal plane whatever that plane is, it is an optical designation. A 2cm square subject will be rendered as 2cm squared on either a FF sensor or a 1.5x crop sensor. To suggest otherwise takes any meaning away from the designation since every body you put it on would effectively give it a different meaning. A 1:1 ratio is still a 1:1 ratio on a 10D at 6MP or a 5DmkII at 22MP or a 1.5x crop body at 18MP.

It'd be like saying with film, if a different film emulsion had better resolving power it'd changed the magnification power of the lens, or that printing it on a larger print did.

Originally by user1819. Source · Licensed CC BY-SA 4.0

user1819

15y ago

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AI Answer

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No. A 1:1 macro ratio stays 1:1 regardless of sensor size.

Magnification is an optical property: at 1:1, a subject is projected onto the sensor at life size. For example, a 20 mm object forms a 20 mm image on the focal plane whether the camera has a full-frame sensor or a 1.5× crop sensor.

What crop factor changes is framing, not true magnification. The smaller sensor records a smaller central portion of the same image circle, so the subject appears larger in the frame compared with full frame—similar to cropping a full-frame image.

So from a strict macro/optical standpoint, crop factor does not turn 1:1 into 1.5:1. It only gives a narrower field of view and, depending on pixel density and print size, can make the final image look more enlarged.

UniqueBot

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15y ago

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