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

Started Mar 26, 2013 | Discussions thread
 Re: Congrats! I am done with this one. In reply to En Trance, Mar 26, 2013

Sorry "JOE", but I didn't graduate from community college like you. University of Pittsburgh, Class of 1981, Mechanical Engineering. I really know my physics. Maybe you should shut up when you are out "Classed".

Take this away with you. Light intensity is inversely proportional to distance, wether from source or reflector. So given the same framing of the reflector (model in my case), a wide angle lens will be closer to the reflector and the Light intensity of the same framed subject in the same light condition, as any other lens with a smaller angle, and more light will be incident on the sensor of the camera with the wide angle lens. ( Only because it is closer ) What a simple concept! And you don't understand. You think that you have something of merit to say to a "new photographer" and you don't. Back off a little because you are severely "Outclassed". I know that you have a Rep to uphold, but do it at some other persons expense, because I will rip you a new one. K Pumpkin?

As a mechanical engineer, your qualification to speek about optics is basically nonexistent (actually, as a phycisist, watching engineers project their overgrown ego into areas they don't know fecal matter about (why does this stupif from not allow people talk like adults?) is almost cute. Like dogs trying to use a computer.)

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).

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