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04-13-2009, 09:34 AM   #1
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Light-readings off in full-manual

Just noticed this a few hours ago, after using my K10D for the first time in a month:

When in full-manual mode the light-meter reads too high. ie: a reading of balanced light (middle of range) produces an overexposed shot, while an adjustment of three stops under is needed to actually get a well-balanced exposure. This seems to apply across all ISOs and shutter speeds.

No known changes to any settings since the last time I used it.

Any suggestions as to problem and solution? Thanks in advance.

04-13-2009, 12:19 PM   #2
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Are you metering in stop down manual mode (aperture set using aperture ring on the lens)? If so, there are well-documented metering issues on the K10D and K20D. The degree of inaccuracy is dependent on the chosen aperture and on the lens being used. The exact cause is not well understood, but appears to be related to the focus screen and how meter readings are handled in stop-down vs. "A" metering.

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04-13-2009, 03:38 PM   #3
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As Steve said, if you are using an M or "K" lens this is well documentd and is variable depending on the maximum aperture of the lens you are using. If however this happens with a lens that can transmit aperture info to the camer (ie a modern lens) then you have bigger problems.
04-13-2009, 05:43 PM   #4
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Lens is meant to be in "A" at all times, but now you've got me wondering if I've somehow managed to flick it off that setting and not notice. Will check it when I get home.

Otherwise, I've got bigger problems I guess!

04-14-2009, 08:55 AM   #5
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What lens are you using ?
04-15-2009, 08:43 PM   #6
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QuoteOriginally posted by pschlute Quote
What lens are you using ?
Sigma 28-80 AF.

Heads up: I had a quick glance at the lens last night and lo and behold I have indeed flicked it off "A". So I'm guessing that would account for the anomaly. Will test it when I can (had no time last night) and get back to you.
04-16-2009, 12:49 AM   #7
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I think that for lenses with an A setting, you need to use the A setting. I seem to remember the aperture ring wont work.

04-16-2009, 04:38 AM   #8
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the K10D, from my experience, has a problem with respect to metering manual apature lenses.

I documented this in the following post,
https://www.pentaxforums.com/forums/241716-post69.html

the same behavior occurrs when you take an automatic apature lens out of the A position.

my suspicion is that pentax uses the apature information from the lens to "calibrate out" most of the exposure error, but when you take the lens out of A mode, this function is disabled. I demonstrated this once with my 70-200 F2.8 sigma lens also.

if you are over exposing in manual, I suspect you are shooting at apatures of F5.6 and smaller
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