Is there something that is the opposite of a teleconverter?

Question

I shoot a Nikon D80 that has a 1.5 crop factor. I'd like to find something like a .67x teleconverter so any full format lens I attach would then have their original focal length and would in theory be faster. Does such a thing exist? If not, is it a matter of physics or patents/marketing/business/etc?

Edit: Thank all of you for the information so far! If I'm understanding things correctly it isn't possible to make a simple focal reducer for DSLRs, but is it possible to make one with some complicated optics? Do focal reducers exist for Nikon F mount cameras, even if they don't aid or slightly reduce image quality?

Would it be possible to have a DSLR camera body specifically designed to have the properties of having a built in focal reducer? Eg a camera body with a reduced size sensor, but having it moved, and the body would require full frame lenses.

see this earlier question: http://photo.stackexchange.com/q/33988/6789 — DHall, Apr 26 '13 at 18:26
The link above probably does answer your question, though this isn't really a duplicate. — Joanne C, Apr 26 '13 at 18:32
Particularly, Matt Grum's answer covers why this only exists for new mirrorless cameras and not DSLRs like your D80. — mattdm, Apr 26 '13 at 18:45
focal reducers are used all the time in astrophotography. Of course, the large packaging in telescopes makes this simpler. — Paul Cezanne, Apr 26 '13 at 20:41

score 1 · Answer 1 · answered Apr 27 '13 at 02:59

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Yes, there is. Metabones offers the SpeedBooster.

answered Apr 27 '13 at 02:59

camflan

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score 0 · Answer 2 · answered Apr 26 '13 at 20:11

Short answer, you would need another lens to focus down the light where as teleconverters just let it expand further before reaching the sensor. The additional lens would have to be back far enough that it would likely interfere with the shutter unless you do some serious additional optics to both move the lens forward and also shrink the focal area of the lens. Adding a bunch more glass is likely going to negate any quality gain.

Is there something that is the opposite of a teleconverter?

2 Answers2

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