I have been wanting something like this for ages (wide angle converter that's behind the lens)

Started Jan 14, 2013 | Discussions thread
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Joseph S Wisniewski
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Aperture is a physical measurement or definition
In reply to Russell Evans, Jan 17, 2013

Russell Evans wrote:

MightyMike wrote:

Russell, if you can believe that a 1.4x rear tele converter will lose you a stop of light and there is no one arguing that point. you then also have to believe a 0.71x rear wide angle converter will gain you a stop of light. a 35mm F2.0 on FF will give you x amount of light over a given area, that same 35mm F2.0 on APS-C will also give you that same x amount of light over a smaller area. the density of light hasn't changed. however when you take x amount of light on a FF sensor and compress it into a smaller area such as an APS-C sensor you're now all of a sudden increasing the density of that light by a factor of 1.5x (lets say 1.4x as thats what the adapter claims) essentially you're adding a whole stop of light over a given area. and that 35mm F2.0 becomes a 24mm F1.4 on an APS-C with a speed booster.

Sure. I think I was reading "brightness" in a different way, more as it has been used in the past as aperture. I probably am also looking at it a little differently as well as a change in the scale in the gain applied to the output. Aperture is a physical measurement or definition,

Yes, it is. The f ratio is diameter/focal length. The wide converter reduces focal length, and it doesn't reduce diameter, so the f ratio decreases, exactly according to the definition.

so to me is seems wrong to use nomenclature that perverts the meaning.

This is not being done.

That's my point I guess, although I can't really come up with a better way to talk about it.


It just seems from reading a lot of different posts, that people are switching back and forth, even in the same post, when talking about aperture or DOF and making the adapter sound like it is doing a lot more than it is.

It's doing exactly what it is doing, in compliance with the laws of physics and the definition of the f ratio.

Thank you

You're quite welcome.

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

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