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08-23-2010, 07:37 AM   #1
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K20D overexposure

In the past few weeks that my K20D with Katz Eye focusing screen has begun overexposing by several stops. This happens both my DA 18-55mm f/3.5-5.6 AL, and my A-series manual-focus lenses, and my M-series manual-focus lenses. (I FWiW, I don't use the "green dot" to determine exposure with M-series lenses; I use the DoF-preview in Manual Exposure mode.) The overexposure seems to be consistent and I need to dial-in two or three stops of negative exposure-compensation or meter in manual-mode to compensate.

My K20D has firmware revision 1.03, and I tend to use the camera in spot-meter mode.

Here's a 2MP sample image (with intact metadata; 1MB) made with the camera in "P" mode with the DA 18-55mm f/3.5-5.6 AL:

http://mcfaddenphoto.com/temp/K20D_auto_exposure.JPG

Any ideas about what has happened? Is a trip back to Pentax in order?

08-23-2010, 08:07 AM   #2
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The chances are the problem is you are having is using spot metering with the Katz Eye screen. The split screen focus in the center is a known problem. Refer to the Katz Eye web site and read their test results. I have one on my K20D also and spot metering is inconsistant to say the least. If you were having good results before, I would suspect you were lucky in the placement of the split screen and it has shifted a miniscule amount. Getting it back to where it was would be trial and error and unreliable.
08-23-2010, 09:15 AM   #3
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The above post is bang-on, the katz-eye site even admits to this.

See if center-weighted metering helps.

If anything, that should give you an underexposed image, as the k20d's meter is fairly conservative.
08-23-2010, 09:22 AM   #4
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It now a trio...

Spot metering with the Katz Eye (or any other split image screen) is a no-no.


Steve


(Owns the Katz Eye, but seldom uses spot metering)

08-24-2010, 06:14 AM   #5
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Thanks for the replies about spot-metering and the Katz Eye. I will certainly visit the Katz Eye website and read their test results and I will do some tests with the camera set to use center-weighted metering.
08-25-2010, 06:36 AM   #6
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A set of quick snaps with the camera set to center-weighted metering were properly exposed. I tried both my auto-focus and manual-focus lenses.

I did find the caution on the Katz Eye website against using spot-meter mode. I think I must have seen that before I installed my Katz Eye but I must have forgotten it.

I think you guys have solved my problem--many, many thanks!

William
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