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

Started Mar 26, 2013 | Discussions thread
This thread is locked.
Joseph S Wisniewski
Forum ProPosts: 33,874Gear list
You can not design a lens that makes me wrong.
In reply to mike703, Mar 26, 2013

mike703 wrote:

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.

Well, I sure can. I've only designed six objectives, and maybe ten relay optical systems or Galilean systems, but I'm not bad.

But no one has to design a new lens to prove the OP wrong. Existing ones do that, quite well.

Hard to imagine a photographer who doesn't know "Suny 16", though.

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?

He's also a PE. Amazing what went right by him. I feel embarrassed for my profession.

-- hide signature --

Rahon Klavanian 1912-2008.
Armenian genocide survivor, amazing cook, scrabble master, and loving grandmother. You will be missed.
Ciao! Joseph
www.swissarmyfork.com

 Joseph S Wisniewski's gear list:Joseph S Wisniewski's gear list
Canon PowerShot S100 (2000) Canon PowerShot S400 Canon EOS 5D Mark II Nikon D90 Nikon D2X +38 more
Post (hide subjects)Posted by
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark post MMy threads
Color scheme? Blue / Yellow