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10-27-2008, 09:59 AM   #1
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Over exposure with K10D

Hi,

I am also having exactly the same problem with my K10D similar to the one posted herehttps://www.pentaxforums.com/forums/pentax-dslr-discussion/40387-k20d-overexp...tml#post377305.

I really do not know what mistake I am doing. but more than 90% of the pictures I take are over exposed. I use AF to lock exposure. I use Central point AF and not 9 point. there is some issue with auto focus. It works only on AF.C. I use various ISO. I was using green mode setting. some are ok. but the faces are over exposed. It is always yellow. the sky is always white. I can post picture later.
It always fixes the aperture to 4. I do not know why? When I change to User mode also the exposure was not correct. I played with aperture and sensitivity and shutter speed. I am unable to find the right combination.

I was using a FA lens in A settings. When I change the A to any other thing the pictures are disasters.
I am beginning to feel it may be the lens error. but how can I work on this to rule out the possibility.

10-27-2008, 10:44 AM   #2
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QuoteOriginally posted by istDL-K10D Quote
Hi,

I am also having exactly the same problem with my K10D similar to the one posted herehttps://www.pentaxforums.com/forums/pentax-dslr-discussion/40387-k20d-overexp...tml#post377305.

I really do not know what mistake I am doing. but more than 90% of the pictures I take are over exposed. I use AF to lock exposure. I use Central point AF and not 9 point. there is some issue with auto focus. It works only on AF.C. I use various ISO. I was using green mode setting. some are ok. but the faces are over exposed. It is always yellow. the sky is always white. I can post picture later.
It always fixes the aperture to 4. I do not know why? When I change to User mode also the exposure was not correct. I played with aperture and sensitivity and shutter speed. I am unable to find the right combination.

I was using a FA lens in A settings. When I change the A to any other thing the pictures are disasters.
I am beginning to feel it may be the lens error. but how can I work on this to rule out the possibility.
So AF only works in AF_C mode. And exposures are bad... Ever think of just sending it in for repairs?
10-27-2008, 10:53 AM   #3
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when you post the pictures, please add some information like type of metering (matrix, center weighted or spot) and the focus point position in the picture during the metering process.
10-27-2008, 01:24 PM   #4
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QuoteOriginally posted by istDL-K10D Quote
Hi,
I really do not know what mistake I am doing. but more than 90% of the pictures I take are over exposed. I use AF to lock exposure. I use Central point AF and not 9 point. there is some issue with auto focus. It works only on AF.C. I use various ISO. I was using green mode setting. some are ok. but the faces are over exposed. It is always yellow. the sky is always white. I can post picture later.
It always fixes the aperture to 4. I do not know why? When I change to User mode also the exposure was not correct. I played with aperture and sensitivity and shutter speed. I am unable to find the right combination.
It's hard to say for sure. Either the camera is very messed up or you have some misunderstandings about what it is suppsed to be doing.

For instance, when you say you use AF to lock exposure, what do you mean? Do you mean you have the custom option set to lock exposure when AF is locked? If so, do you understand that this means

When you say AF works only on AF-C, what happens if you try it on AF-S? Does the lens rotate at all? Or does it just fail to lock? Or does it appear to lock but result in in out of focus pictures?

As for aperture being fixed at 4 - what exposure mode are you in, and how are you trying to change the aperture? In Av or M modes, the aperture *should* stay in one place if you don't move the dial.

QuoteQuote:
I was using a FA lens in A settings. When I change the A to any other thing the pictures are disasters.
That's because when you move the lens off "A", you need to use M mode and hit the Green button to cause the camera to stop down, meter, and set shutter speed.

QuoteQuote:
I am beginning to feel it may be the lens error. but how can I work on this to rule out the possibility.
Frankly - and no offense intended - I'd say, find someone who definitely knows how to work the camera to see if they notice these problems. At this point, it's hard to rule out the possibility that the problem being something you are doing wrong that you don't yet realize.

10-27-2008, 01:53 PM   #5
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You were working it on Green mode.

1) Maybe try "P" and see what happens.

2) You might have your metering set to spot. I did that once but everything was underexposing and I was wondering why. Then I set it to Multi-segment and everything worked fine.
10-28-2008, 09:05 AM   #6
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Sabatella
Even though I am not an expert, I am learning photography. please see my signature to see some of the pictures I took using istDL.

This K10D works fine for few shots and over exposes many other. If it is consistently producing either over exposed or underexposed pictures then every thing is wrong. the person, the camera etc.

There are few glitches. the camera has a small lever problem with AF.S and AF.C. due to that it works only AF.C. no manual focus either. see my earlier thread. (https://www.pentaxforums.com/forums/pentax-dslr-discussion/39409-new-k10d-stuck-mf.html

I was taking pictures of a parade. people are walking. so I was getting inconsistent exposures. when I lock the AE with AE Lock and the people move before I take the picture, the problem occurs. when I take stationary pictures of a tree or some thing the pictures are ok. I mean they are usable.

I was taking pictures in green mode, P mode and User mode (with Aperture ring set to A). It was around 9-10 am. so the sun is coming up and we are standing near a building. so it is uneven brightness. in green mode every picture was taken at F 4.0 (it was supposed to be either 8.0 or even 11). I am sorry I could not post the pictures right now. otherwise it will clear your doubts.

I am not having that many issues when I take indoor pictures.

I can get it checked and corrected by pentax (that is my last option). I do not want to miss halloween and color change. so I am trying to fix before sending to pentax.

Marcus
I was using center weighed metering for all my pictures. may be I should check up the multi segment one. thanks for the suggestion.
10-28-2008, 01:12 PM   #7
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QuoteOriginally posted by istDL-K10D Quote
I was taking pictures of a parade. people are walking. so I was getting inconsistent exposures. when I lock the AE with AE Lock and the people move before I take the picture, the problem occurs.
I think the lock only stays effective for a fixed period of time? In any case, I'd recommend M mode to get more consistent reuslts - once you set exposure, *nothing* will change it except you. And as long as the light doens't change, you can pretty much just set the exposure once and then start shooting. Adjust by a stop or so when moving from full sun to shadow, ad don't worry about re-metering every shot.

QuoteQuote:
in green mode every picture was taken at F 4.0 (it was supposed to be either 8.0 or even 11).
In Green mode, you have no control over aperture, so I'm not sure what makes you say it was "supposed" to be at f/8. But I'd agree it would strange that the camera would always choose f/4, unless you're dealing with low light, and that's the widest aperture you have. Could be something wrong with the contacts between the camera and lens such that the camera is under the mistaken impression that f/4 is also the *smallest* aperture you have. Actually, that could explain overexposure in bright sun, too...
10-28-2008, 01:22 PM   #8
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What metering mode are you using? Spot? Center Average? Multi Segment?

10-28-2008, 02:07 PM   #9
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If I read your initial post correctly, this happens when you have the aperture ring at other than "A". Correct?

Assuming you said yes, you should be using M mode and the green button. P or AV mode will default to AV, maximum aperture only.

Also:
  • Your AF settings do not influence exposure mode
  • When setting the aperture using the aperture ring on the lens, your metering will be limited to center-weighted and spot only. Matrix metering is disabled.
  • Depending on the lens, your exposure may still be somewhat unreliable at the extremes of the f/stop range when using the aperture ring. One of my lenses has a 2-3 stop exposure bias wide open at f/2 that partially resolves by f/4 with accurate metering at f/5.6 and beyond.

Steve
10-29-2008, 08:23 AM   #10
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Here is the detailed images.
There are couple of other images too.
K10D experiment - a set on Flickr

The naming is self explanatory. If you see most of the green mode shots are over exposed. The lens was set at "A" mode only.

The 3 starwar characters is a good example for wrong exposure in green mode. It is hard to explain why the green mode chose slower shutter speed with wide aperture for bright sun light. no clue.

There are few other pictures which are difficult to explain the wrong exposure.

I have 4 pictures M_SM_black, M_SM and M_CW_black, M_CW. Every thing remains the same except the center point is little different. When the center spot is little dark the pictures are underexposed and when the center spot is not dark the pictures are over exposed???.

I have also changed my focusing screen and using a split screen. there is little improvement in the exposures. but that is no way consistent like my istDL.

I did see some improvement in changing from spot metering to center weighed but multi segment is not so consistent.

More over in the green mode when I use FA lens with other than aperture ring set to "A" my auto focus does not work. Is there a setting I should change to enable it, I do not know.

I am using either M or User mode to change the aperture value to take pictures in "A" (setting in apeture ring).

I took two shots with SR on and off at 1/5th of the second and the pictures are fine.
http://www.flickr.com/photos/31661649@N06/2984442076/in/set-72157608481468329/

http://www.flickr.com/photos/31661649@N06/2983585451/in/set-72157608481468329/

Last edited by istDL-K10D; 10-29-2008 at 08:33 AM.
10-29-2008, 09:06 AM   #11
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QuoteOriginally posted by istDL-K10D Quote
The 3 starwar characters is a good example for wrong exposure in green mode. It is hard to explain why the green mode chose slower shutter speed with wide aperture for bright sun light. no clue.
The picture of Darth Vader says it was taken using spot metering. If you spot metered off a black object, the exposure you got as a result is pretty much *exactly* what should be expected.

I checked quite a few others, and almost *all* seem to have been spot metered, and all of them came out pretty much exactly as should be expected when using spot metering. Most overexposed because you metered off a dark object, some (like the purse) underexposed because you metered off a white object.

Conversely, the few pictures I saw that used center-weighted multi-segment metering were of a scene dominated by a white background. And exactly as it is supposed to, the camera rendered the scene as approximately the equivalent of 18% gray on average - which is to say, quite a bit darker than it actually appeared. That's the way cameras are *supposed* to work when metering off white objects; you're *supposed* to have to dial in positive exposure compensation. I would highly recommend checking out a book on exposure to learn more.

QuoteQuote:
I did see some improvement in changing from spot metering to center weighed
Well, *of course*! Spot metering is not a mode you should be using unless you understand how to use it - how to choose an appropriate subject for the metering before actually composing your photo. Simply pointing directly at the subject and shooting using spot metering is *supposed* to produced results pretty much exactly as you got. Center-weighted or multi-segment metering are much more appropriate for using as a "point and shoot", except even then, you need to know that when dealing with light colored (or dark colored) scenes, you'll need to dial in exposure compensation.

QuoteQuote:
More over in the green mode when I use FA lens with other than aperture ring set to "A" my auto focus does not work. Is there a setting I should change to enable it, I do not know.
No, as long as you don't change the AF switch to MF, it should still auto-focus even when not in the "A" position, as far as I know. However, I suspect it won't be able to use any but the center focus point.
10-29-2008, 09:08 AM   #12
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can I make a suggestion?

as the title implies, I have a suggestion.

let's go back to basics.

I assume you have a K10D with manual apature lenses.

go out and find a place where there is a nice uniformly lit surface. My preferences are side walks, block walls and paved roads.

with the K10D set to manual mode. spot metering, and your manual lens set wide open, adjust the ISO so that you have a shutter speed between 1/2000 and 1/3000. when using the green button (note green button control should be set to change shutter speed)

Take a shot using the green button at each F stop detent on the apature ring.

Post the grey scale values for each frame.

you should expect to see something like the chart in the attached post.

https://www.pentaxforums.com/forums/241716-post69.html
10-29-2008, 09:53 AM   #13
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QuoteOriginally posted by Marc Sabatella Quote
The picture of Darth Vader says it was taken using spot metering. If you spot metered off a black object, the exposure you got as a result is pretty much *exactly* what should be expected.

I checked quite a few others, and almost *all* seem to have been spot metered, and all of them came out pretty much exactly as should be expected when using spot metering. Most overexposed because you metered off a dark object, some (like the purse) underexposed because you metered off a white object.
I was also under the same impression. but did you check the other 4 pictures I mentioned. (I have 4 pictures M_SM_black, M_SM and M_CW_black, M_CW. Every thing remains the same except the center point is little different. When the center spot is little dark the pictures are underexposed and when the center spot is not dark the pictures are over exposed???.)
the dark objects produced underexposed picture and the bright object produced over exposed pictures.

QuoteOriginally posted by Marc Sabatella Quote
Conversely, the few pictures I saw that used center-weighted multi-segment metering were of a scene dominated by a white background. And exactly as it is supposed to, the camera rendered the scene as approximately the equivalent of 18% gray on average - which is to say, quite a bit darker than it actually appeared. That's the way cameras are *supposed* to work when metering off white objects; you're *supposed* to have to dial in positive exposure compensation. I would highly recommend checking out a book on exposure to learn more.
I agree I need to learn more about exposures. but should the camera behave so differently if there is very small difference in the dark/white area?. I am sorry I may be dumb. but again why this happens only with K10D? (which is supposed to be a better camera than ist series)

QuoteOriginally posted by Marc Sabatella Quote
Well, *of course*! Spot metering is not a mode you should be using unless you understand how to use it
that pretty much summarises my problem.


QuoteOriginally posted by Marc Sabatella Quote
No, as long as you don't change the AF switch to MF, it should still auto-focus even when not in the "A" position, as far as I know. However, I suspect it won't be able to use any but the center focus point.
that is ok. but when I change the dial to other than "A" I see MF in my view finder.

Thanks for your inputs.

Lowell Goudge
I am using FA lens and not a manual M42.
10-29-2008, 11:34 AM   #14
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QuoteOriginally posted by istDL-K10D Quote
I was also under the same impression. but did you check the other 4 pictures I mentioned. (I have 4 pictures M_SM_black, M_SM and M_CW_black, M_CW
It is not clear to me how to find these pictures - there did not appear to be any direct links to them?

QuoteQuote:
Every thing remains the same except the center point is little different. When the center spot is little dark the pictures are underexposed and when the center spot is not dark the pictures are over exposed???.)
In spot metering I'd expect precisely the opposite, but perhaps seeing the pictures would be "illuminating".

QuoteQuote:
but should the camera behave so differently if there is very small difference in the dark/white area?. I am sorry I may be dumb. but again why this happens only with K10D? (which is supposed to be a better camera than ist series)
The whole point of spot metering is, as the name implies, to meter off a specific spot. So a small change in the framing of the picture can change that spot from dark to light, which would indeed have a huge effect on the exposure. If you have another camera with spot metering that *doesn't* work that way, perhaps it is dealing with a much larger spot than the K10D. Generally, when using spot metering, the smaller the spot, the better, as you are *supposed* to be able to pinpoint it and not have surrounding areas affect the exposure.

In center weighted metering, you should see a small effect from these slight changes in viewpoint. In multi-segment, you should see a relatively small change also, *unless* you are using the link AF and AE point custom option, in which case you might expect bigger changes.

QuoteQuote:
that is ok. but when I change the dial to other than "A" I see MF in my view finder.
Hmm. I have no FA lens to test with, so I can't say for sure that this is not right. But it does surprise me.
10-29-2008, 11:49 AM   #15
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QuoteOriginally posted by Marc Sabatella Quote
It is not clear to me how to find these pictures - there did not appear to be any direct links to them?
M_SM (center on russia)
M_SM on Flickr - Photo Sharing!

M_SM_black
M_SM_black on Flickr - Photo Sharing!


M_CW (center white spot)
M_CW on Flickr - Photo Sharing!


M_CW_black (center black spot) http://www.flickr.com/photos/31661649@N06/2984441862/in/set-72157608481468329/
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