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02-06-2011, 11:33 AM - 1 Like   #1
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Aperture on Pentax-A lens

I'm using a Pentax-A 1:2 50 mm on a K200 on the AV setting.

On the lens itself, the f-stops go
2 - 2.8 - 4 - 5.6, etc.
When I control the aperture setting with the camera, the f-stops go
2 - 2.2 - 2.5 - 2.8 - 3.2 - 3.5 - 4.0 - 4.5 - 5.0 - 5.6, etc.

Can I use those intermediate apertures (like 2.2 & 2.5 for example) that aren't labeled on the lens?

When I manually change it, the lens goes from 2 to 2.8 with nothing in between. There is a stop between 2.8 and 4, however, even though it's not labeled on the lens.

Thanks in advance for your help

02-06-2011, 11:38 AM   #2
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Yes, you can. You've got your camera set to show 1/3rd stops and that is exactly what it is doing. The actual stops on your lens are just where the "click" stops are. The actual; aperture changes incrementally inbetween the clicks.
02-06-2011, 12:33 PM   #3
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The clicks are as far as you can go with in-between apertures.
Some lenses have clicks that others don't. So yours cannot be set between f/2 and f/2.8, but can be set to f/3.5, which is half a stop above f/2.8 and below f/4.
The camera electronically sets the aperture for you when in A mode on the lens, so it's able to accurately set those intermediate apertures and bypass the manual stops.
02-06-2011, 02:18 PM   #4
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QuoteOriginally posted by Ash Quote
The clicks are as far as you can go with in-between apertures.
Huh? My "A" lenses can be set in-between clicks if you really need to. The iris mechanism has continuous operation and will stop down based on ring position regardless of whether you are on a full/half stop notch or somewhere in-between.



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