Nikon Macro Lens, effective aperture

Started 2 months ago | Discussions thread
bclaff Forum Pro • Posts: 10,108
Re: Nikon Macro Lens, effective aperture

JHern wrote:

Deriving the simple formulas is easy when we can assume that the light rays are parallel to the lens axis...while this is only strictly true for objects at infinity, it is a very good approximation until one gets close. As the objects get closer, the light rays are not parallel to the lens axis, but rather are spreading outward (diverging) on their way from the subject to the entrance pupil, and this is the geometric context that can be used to derive the correction factor for aperture. I've never done the full derivation, but I should sit down and work it out for my own curiosity. Will follow this thread...

Keep in mind that effective aperture is all about the exit pupil, not the entrance pupil.

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

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