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10-27-2020, 05:49 PM   #46
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QuoteOriginally posted by photogem Quote
The test is crucial, because it gives right away an answer: Either the solenoid is stuck or it works.
The test does exactly that and then one knows.
And in 99% of all dark image problems with a Pentax DSLR since the K30 and using a solenoid this is the very culprit.
I agree- at last we have an understanding. So I hereby reinstate my advice for the test. I had it in mind to do so anyway, and also to look into any answers to my question about how using Av mode with an aperture ring would work, but I have been busy with other important matters.

---------- Post added 10-27-20 at 05:55 PM ----------

QuoteOriginally posted by m42man Quote
A strange quirk seems to be that, with an afflicted K-50, you can set Av mode, with Aperture Ring Enabled, and the camera will stop the lens down to the aperture set by the aperture-ring when the shutter is fired. This is not the behaviour you get with a healthy camera.

This is very handy, but as far as metering is concerned, the camera has no knowledge of the set aperture, so assumes the same aperture as when metering was done - i.e., wide-open. So, in order to get the correct exposure, you need to use exposure compensation. For example, if you're using an f2 lens set to f4, you need to set +2EV compensation. Works a treat, and exposure is accurate, as this apes normal operation (unlike stopped-down metering with the green button).
If one must still use exposure comp, the range of aperture choice would surely be limited, as based on departure from wide open. It is too bad Pentax did not continue their design as with some of their later AF 35mm film models, which could use either the camera's aperture control or the aperture ring. I have two such models, and there is no need to do anything but simply engage the aperture ring, and it works perfectly. And one of these was not an expensive model!


Last edited by mikesbike; 10-27-2020 at 06:29 PM.
10-28-2020, 03:37 AM   #47
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QuoteOriginally posted by mikesbike Quote

If one must still use exposure comp, the range of aperture choice would surely be limited, as based on departure from wide open. It is too bad Pentax did not continue their design as with some of their later AF 35mm film models, which could use either the camera's aperture control or the aperture ring. I have two such models, and there is no need to do anything but simply engage the aperture ring, and it works perfectly. And one of these was not an expensive model!
Well, you have 5 stops to play with, so up to f11 for an f2 lens, f16 for an f2.8 lens, f22 for an f4 lens, etc. I think the biggest drawback is when you are using a variable-aperture zoom...
10-28-2020, 01:34 PM   #48
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QuoteOriginally posted by m42man Quote
Well, you have 5 stops to play with, so up to f11 for an f2 lens, f16 for an f2.8 lens, f22 for an f4 lens, etc. I think the biggest drawback is when you are using a variable-aperture zoom...
Yes, that's right. Off the top of my head I was thinking along the lines of some old cameras where 3 stops was the limit. I checked, and it is indeed 5 stops now. I do use exposure comp, but no where near those limits. Not too bad for range, but again you're right- most zoom lenses being variable-aperture. But then when in Av mode, would the camera not respond by changing the shutter speed? I know the aperture ring with a variable-aperture lens is problematic even with a healthy camera, when using the Manual mode. In times past, camera models were typically designed only for aperture ring use, so I found it best to buy a constant-apeture zoom lens if possible.
10-29-2020, 12:34 AM   #49
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QuoteOriginally posted by mikesbike Quote
Yes, that's right. Off the top of my head I was thinking along the lines of some old cameras where 3 stops was the limit. I checked, and it is indeed 5 stops now. I do use exposure comp, but no where near those limits. Not too bad for range, but again you're right- most zoom lenses being variable-aperture. But then when in Av mode, would the camera not respond by changing the shutter speed? I know the aperture ring with a variable-aperture lens is problematic even with a healthy camera, when using the Manual mode. In times past, camera models were typically designed only for aperture ring use, so I found it best to buy a constant-apeture zoom lens if possible.
What is happening is that the camera meters with lens wide-open, just like Av mode with a normal camera. The difference is that, in normal operation, the camera will know the aperture that will be used for taking the shot, so can calculate the correct shutter speed for taking the shot. When you take a shot with an afflicted camera, you're using the aperture ring - only you know what the target aperture is. So, you calculate the difference between wide-open and stopped down target aperture - and, in general, you can't do that accurately with a variable-aperture zoom (and in any case, you'd be having to change Compensation as you change zoom setting - inconvenient at best).

10-29-2020, 11:38 AM   #50
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Ugh- bummer!
10-29-2020, 11:59 AM   #51
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QuoteOriginally posted by m42man Quote
A strange quirk seems to be that, with an afflicted K-50, you can set Av mode, with Aperture Ring Enabled, and the camera will stop the lens down to the aperture set by the aperture-ring when the shutter is fired. This is not the behaviour you get with a healthy camera.
I think this is explainable. When the solenoid is broken, the lens tries to 'shut down' to its smallest opening. With a "DA" lens, that means the smallest opening the lens is capable of, and the image looks "dark", but if the lens has an aperture ring, the smallest opening will be the value that the lens's aperture ring is set for.
10-29-2020, 02:44 PM   #52
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QuoteOriginally posted by reh321 Quote
I think this is explainable. When the solenoid is broken, the lens tries to 'shut down' to its smallest opening. With a "DA" lens, that means the smallest opening the lens is capable of, and the image looks "dark", but if the lens has an aperture ring, the smallest opening will be the value that the lens's aperture ring is set for.
Yes - that's why Manual mode with the green button for stop-down metering works (i.e. the official method).

But try using Av mode with a healthy K-50 (or any other Pentax DSLR), with a K-mount lens, using the aperture ring, and you'll find that the lens doesn't stop down. All shots are wide-open.

The peculiarity is that a K-50 with aperture block failure behaves the way that it does.
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