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02-28-2015, 08:10 AM   #1
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Exposure issue with K-50

I was testing out a few vintage lenses that I recently acquired this morning and noticed something regarding the aperture control on my K-50 that concerned me. I took test shots with the following two sets of settings with multiple lenses and the problem seemed to persist throughout.

1) Lens aperture ring set to "A", aperture set to f/8 on the camera, shot taken in Av mode.

2) Lens aperture ring turned to f/8, metering done with the green button in M mode, shot taken in M mode

The shots from scenario 1 are consistently more exposed than those from scenario 2 even though the two metering methods yielded the same exposure time according to the camera display. When pixel peeping the shots from scenario 2 are all consistently sharper than those from scenario 1. It makes me wonder if the first method is somehow allowing the exposure to start before the lens aperture is physically stopped down by the aperture lever of the camera. If the exposure starts slightly early then part of the light hitting the sensor would be from a wider aperture which would result in less sharpness and increased exposure.

Is this some kind of known issue? Any ideas or information would be appreciated.

02-28-2015, 10:38 AM   #2
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Im sure someone else will come along in a bit and give you a detailed answer but off the top of my head I think old glass has to be in M mode otherwise it will shoot everything fully wide open no matter what you try to set the aperture to.
02-28-2015, 10:44 AM   #3
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QuoteOriginally posted by MADDSNIPER Quote
Im sure someone else will come along in a bit and give you a detailed answer but off the top of my head I think old glass has to be in M mode otherwise it will shoot everything fully wide open no matter what you try to set the aperture to.
"A series" lenses meter wide open on the digital bodies and do not need a stop down (green button) step.
However A lenses do see to over/underexpose at times. The M (stop down) method seems a little more accurate but more troublesome to me.

OP: Was this with the same lens or different lenses when you saw the same exposure listed but diffeent results?
Remember that the A setting has the camera press the aperture level to an approximation of the f/stop using a formula, the M method uses preset f/stops and the camera just has to swtich (on/off0 vs. the precision needed for A lenses..
02-28-2015, 11:57 AM   #4
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Forgive me if these suggestions are trivial and/or you have already checked them:

Did you reset your exposure compensation in Av mode back to 0?
Did you change the settings for the green button to be Tv shift for using manual aperture?
Did you enable the use of aperture rings in the custom settings menu?
Is the ISO making the difference? In manual mode, are you setting the ISO to exactly what it was in the Av mode?

That's my 2 cents. Hope it helps narrow it down.

02-28-2015, 05:47 PM   #5
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Stop down metering with manual lenses (smc M so far for me) tends to be conservative and underexposes on k-50 (might be slightly sluggish aperture though). I've never been happy with the stop down metered images I've taken, so I use one stop down shot as a test and then adjust to compensate in manual mode settings for a better overall exposure.

I have a 50mm f/1.4 m42 on the way + an adapter. Once I get these I can test to see if similar exposure results come up. I'm guessing they will. I do not use other modes other than manual or auto, so can't comment on TAV or AV.
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