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03-28-2010, 12:49 PM   #1
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Long exposure confused K20D

I was shooting some macros using a bellows attachment.
At aperture priority mode, a shutter speed of 4 seconds was reached at plus 2EV.
I had to use the M mode and dialed a shutter speed of 6s.
This resulted in a white screen! In other words, an extreme overexposure.
Dialing other speeds or returning to Av mode again did not help.
The camera (K20D) was overexposing whatever I did.
Even turning it on and of did not help.

Removing the bellows attachment and shooting with a proper lens revived the brains of the camera!

Attaching the bellows again and shooting was also OK... until trying the 6s exposure again!
Overexposure... Refusing to shoot normally even when lower speeds were set... Same cycle as above.

The battery looked full.
The camera has no other quirks.

Any ideas?

03-28-2010, 02:23 PM   #2
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So, Av mode wanted to overexpose by 2 stops by using a 4 second shutter. You increased that to 6 seconds and wonder why its overexposed? Maybe I'm not understanding the problem.
03-28-2010, 02:51 PM   #3
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You mentioned using a bellows, so how would the camera figure out the exposure unless you hit the Green button to do a stop down meter reading first? To my understanding of what you've described, there's no way for the camera to know the exposure reading, so using Av mode is pretty much useless. It's like trying to use Av mode with a K or M lens, it will only shoot at maximum aperture.
03-28-2010, 03:43 PM   #4
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You didn't mention the type of lens and bellows. With no aperture automation, then the camera in AV mode, with the lens stopped down, should calculate an exposure. It might be wrong, so you adjust the EV -- which you did. Going to M mode and hitting the Green button might give the same (wrong) exposure, or might not. But going from a calculated 4" to 6" (+0.5 EV) shouldn't cause a whiteout.

I tried somewhat to reproduce your problem. I put an M42 Industar 50mm lens on 50mm of extension, set to f/22 and ISO 200, and metered a not-too-bright subject in both M and Av modes. Both gave a reading of 0.7" which was too dark. I dialed it up to 6", same as you. I shot. It came out a bit overexposed, but no whiteout.

03-28-2010, 10:28 PM   #5
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Original Poster
RioRico,
It was almost exactly as you described and the lens was an Industar too .
I did not try the green button, however.
Will try again and report here.
Thanks to all responders.

ADDED:
This time it happened just once and that was when I had forgotten to narrow the aperture (focusing at f/2.8, shooting at 1/16).
Should have been my mistake from the start...

Last edited by bc_the_path; 03-29-2010 at 01:55 PM.
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