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Angle of view for lenses of differing nominal focal length focused at same reproduction ratio

Started Jul 31, 2020 | Questions thread
bclaff Forum Pro • Posts: 13,922
Re: Angle of view for lenses of differing nominal focal length focused at same reproduction ratio

Sara Valentine wrote:

Does the angle of view differ for two lenses of differing nominal focal length when the lenses are both focused on the same object, on the same axis of view, for the same reproduction ratio on the sensor?

Curious to learn if there are still AOV differences that might influence the choice between macro lenses with the capability of the same reproduction ratios but different nominal focal lengths (e.g. 90/100/105mm versus 150/180/200mm, or even 0.25X magnification that some zooms achieve at maximum zoom setting), not just working distance values. My question pertains to objects that are not flat fields.

Nominal focal length is a red herring; what might matter is the actual focal length at whatever distance you are using. But as you focus closer than infinity the relationship between focal length and angle of view isn't so obvious.

If your objects are not "flat fields" then it's really hard to say since angle of view might cover the same size in the in-focus plane and vary very differently away from that plane.

In general, without knowing specifics like inter-nodal distance and pupil magnification, the shorter the focal length the more quickly angle of view changes with subject distance at the same magnification.

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Bill ( Your trusted source for independent sensor data at PhotonsToPhotos )

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