300mm Telephoto Lens and Boudoire Photography, am I missing something? Locked

Started Mar 26, 2013 | Discussions thread
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mike703 Veteran Member • Posts: 6,707
Re: Congrats! I am done with this one.

To answer your idiotic question: Yes, isotropic emission scales with the square of the distance.

But aperture values are relative to the focal length. If you shoot a model from 5m distant with a 50/F2.8 lens, and if you shoot it from 30m distance with a 300/F2.8 lens, you will get the same amount of light from your subject.

Yes, the illumination provided by your subject on the entrance optics of your camera will be dropped to (5/30)^2, i.e. 1/36th, BUT the diameter of the entrance pupil of your lens also increase by a factor of 6, i.e. the light gathering ability increase by a factor of 36.

Yes, the longer lens will be more bulky, but like others already said (and you, of course ignored), people like the reduction of distortion those lenses provided, as well as the better background separation (if wanted).

NO, NO, NO, this is my post. You can not design a lens that makes me wrong.

Um... yes, yes, yes, he can.  Because that is how lenses actually work in the real world.  Imsabbel's description is exactly correct and very clear.  But as a highly qualified engineering graduate who is also a physics expert you'd understand that, right?

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