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06-21-2011, 05:24 PM   #1
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Help!...Aperture setting making no difference.

This is a P/K mount Kiron lens (No 'A' setting).

When I twist the aperture ring I can see the aperture blades opening and closing.

Then when I shoot with the lens in Av mode it is metering fine, however when the aprture is changed it makes no difference what so ever like the aperture blade being stuck wide open. The iso stays the same, the shutte speed stays the same and even the histogram is identical from f2 to f16, but I can see the aperture blades close...what is going on ??????????

I've had a loooong day and I am exhausted, I am pretty sure I am missing something?

Auto EV compensation is OFF in the menu.


Last edited by pcarfan; 06-21-2011 at 05:30 PM.
06-21-2011, 05:30 PM   #2
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This question was asked recently and can be found here:
https://www.pentaxforums.com/forums/pentax-beginners-corner-q/148873-k-x-manual-lens-av.html
06-21-2011, 05:31 PM   #3
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See also this thread: https://www.pentaxforums.com/forums/pentax-lens-articles/110657-how-use-meter...k-x-k-7-a.html

Note that Av mode can only be used with takumars, not M/K lenses. For metering in M mode, see the instructions.

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06-21-2011, 05:32 PM   #4
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I am having trouble understanding the situation. Is the histogram remaining the same despite the image darkening as a consequence of the smaller apertures?


Last edited by mccarvindh; 06-21-2011 at 05:45 PM.
06-21-2011, 05:44 PM   #5
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QuoteOriginally posted by pcarfan Quote
This is a P/K mount Kiron lens (No 'A' setting).

When I twist the aperture ring I can see the aperture blades opening and closing.

Then when I shoot with the lens in Av mode it is metering fine, however when the aprture is changed it makes no difference what so ever like the aperture blade being stuck wide open. The iso stays the same, the shutte speed stays the same and even the histogram is identical from f2 to f16, but I can see the aperture blades close...what is going on ??????????

I've had a loooong day and I am exhausted, I am pretty sure I am missing something?

Auto EV compensation is OFF in the menu.
Manual (M non A type) lenses only work in M mode.

06-21-2011, 06:02 PM   #6
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QuoteOriginally posted by mccarvindh Quote
I am having trouble understanding the situation. Is the histogram remaining the same despite the image darkening as a consequence of the smaller apertures?
No the images looked the same eventhough I was physically changing the size of the aperture, what I couldn't understand is how could the brightness of th image stay the same when the iso and shutter are the same and the aperture is changing (the actual size of the hole changes), but I presume the picture is taken with the aperture fully open irrelevant of where it is set for M lenses.
06-21-2011, 06:02 PM   #7
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QuoteOriginally posted by jellyfish26 Quote
QuoteOriginally posted by Adam Quote
See also this thread: https://www.pentaxforums.com/forums/pentax-lens-articles/110657-how-use-meter...k-x-k-7-a.html

Note that Av mode can only be used with takumars, not M/K lenses. For metering in M mode, see the instructions.
QuoteOriginally posted by JeffJS Quote
Manual (M non A type) lenses only work in M mode.

Thank you
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