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02-28-2013, 08:39 PM   #1
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What Am I Missing...

if I don't use the Green Button w/MF lenses?

02-28-2013, 09:10 PM   #2
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If it's an A series lens, absolutely nothing. If it's anything else, exposure metering.
02-28-2013, 09:11 PM   #3
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Manual focus or manual exposure? Green button has nothing to do with focus.

In the default mode the green button stops down the aperture, the camera takes a meter reading and then sets the shutter speed to give you a proper exposure at the aperture you selected on the aperture ring. On k-mount manual exposure lenses this is the only way to get a proper exposure as they can only be used in M mode. Well, than can used in Av mode but only wide open, the camera meters wide open and the exposure is always taken wide open.

With m42 lenses you can use Av mode as the aperture is not held open by the camera and you set it real-time with the aperture ring. But M mode and green button is still generally more accurate.
02-28-2013, 09:13 PM   #4
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QuoteOriginally posted by tabl10s Quote
if I don't use the Green Button w/MF lenses?
It isn't manual focus lenses per se, but non-'A' bayonet lenses (those without contacts and no 'A' setting). So if you have a Pentax-M 50mm, for instance, you need to use M mode and you choose aperture (by turning the ring on the lens) and the ISO, and then the green button sets the shutter speed appropriately. Of course you don't *have* to do that -- you can look at the meter +/- and set it yourself.

With 'A' lenses and AF lenses, you don't need it. With m42 screw-mount lenses, you don't need it. Only totally manual K-mounts...

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