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06-14-2019, 06:11 PM   #1
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Aperture block but green button availability

this has been more than likely covered and I have missed it...

I have the K-50 that has the aperture block failure....so I do not use any of my 'A' lenses in that position and typically use M42 lenses.....anyways the other day got a new to me 'M' type lens and placed it on the K-50 to try it out....since I have been using M42s for so long now and more often than not using Av mode with them I had forgotten all about 'M' type lenses only metering wide open......well I switched over to M mode and used the green button for stop down metering....yay nice exposure....ok great then it occurred to me how is it that my aperture blocked K-50 can do stop down metering but cannot close the aperture in 'A' mode?? is it not the same mechanism that stops down on the green button the same mechanism that stops down the lens for a shot?....does it not have to close the aperture if I set the lens to f8? etc......so I guess I missed where the aperture lever works in one manner but will not work in another.....not trouble shooting just a general question

06-14-2019, 07:12 PM - 4 Likes   #2
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In failure mode the aperture mechanism on the body always moves to the full stop-down position, rather than the proportional movement to the set f-stop. The reason lens with aperture rings work is that the aperture ring mechanism stops the iris from closing down past the set f-stop.
06-14-2019, 07:27 PM   #3
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thank you! that sums it up very well appreciate it
06-14-2019, 08:23 PM   #4
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QuoteOriginally posted by Not a Number Quote
In failure mode the aperture mechanism on the body always moves to the full stop-down position, rather than the proportional movement to the set f-stop. The reason lens with aperture rings work is that the aperture ring mechanism stops the iris from closing down past the set f-stop.
Wow! I knew that M42 lenses worked just fine in Av mode on affected cameras, but it had not occurred to me that similar might be true when using the aperture ring in M mode with K-mount lenses.


Steve

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