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05-23-2008, 01:22 PM   #31
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QuoteOriginally posted by TonyC Quote
This is not an issue that would ever concern me because I never use auto exposure on a camera. I use a trial shot followed by a histogram check and after that I work by 'feel' with the occasional histogram check.

However to be fair to this poster this month's UK Professional Photographer magazine slates the K20D for (inconsistently) underexposing in bright situations. They said sky almost always needed +1 stop compensation. Other than that they were positive about every aspect of the camera.

Curiously the photo in the review that is supposed to be an example of this 'problem' shows a perfect (in my opinion) exposure of a very difficult subject. A white waterfall partly in the sun and partly in shade. There is full detail visible in both sun and shady areas - a remarkable performance in my opinion.
Can you please post the link of the review which you mentioned?

05-23-2008, 04:04 PM   #32
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QuoteOriginally posted by mrechte Quote
Also what is your opinion about the 2 couples of pictures 905/906 and 1109/1110? For my opinion I should have got opposite results (higher exposure with the spot measure).
905/906
I ignored this example because of the difficult lighting situation (bright sun in the image). I always bracket such shots. But since you ask...

- 905 is overexposed for the situation (with sun in the image and no EV compensation, IMHO shadows should have come out darker). You should be able to use at least +1EV compensation (possibly plus fill flash) in similiar situations.
- 906 is what I would expect from my K20D (or any other SLR) -- however, I don't use spot metering (my eyes don't do spot metering so I don't let my camera do it -- I prefer EV compensation, depending on whether I shoot into the shadows or the bright area). So, I don't know if this is ok with spot metering on.


1109/1110
I found both images ok so I didn't comment on them. But since you ask...
- 1109 good exposure, almost perfect.
- 1110 green channel clipped in the shadows, would have need +1/3 EV.

So, why is it darker with spot metering? I must admit, I don't know. I guess it all depends on the size of the spot metering zone. If it did only measure the face w/o the shadow on the wall, it may be ok because it actually did do a better job on the face alone (1110 shows much better how your son is suffering from the bright sun )

If I look at the histograms of the first full, and the second center (face) region, then both histograms look ok (unclipped).


Does anybody know the size of the spot metering zone? Is it the size of the circle on the focus screen? Does spot metering possibly favour (red) skin tones?


Let me add two general comments:
It is wise to check histogram right after the exposure (before coming home) and either shoot RAW or use D-Range with JPG in high contrast situations like the ones shown here (both gives you somewhat extra headroom for corrections later on). I hope nevertheless that your images had enough headroom to render them as desired.
05-23-2008, 04:26 PM   #33
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glad you brought that up

QuoteOriginally posted by falconeye Quote
905/906

So, why is it darker with spot metering? I must admit, I don't know. I guess it all depends on the size of the spot metering zone. If it did only measure the face w/o the shadow on the wall, it may be ok because it actually did do a better job on the face alone (1110 shows much better how your son is suffering from the bright sun )





Let me add two general comments:
It is wise to check histogram right after the exposure (before coming home) and either shoot RAW or use D-Range with JPG in high contrast situations like the ones shown here (both gives you somewhat extra headroom for corrections later on). I hope nevertheless that your images had enough headroom to render them as desired.
Even w/ my D the spot meter had a tendency to decrease the exposure by about 1/2 stop. Never checked it thoroughly or did any "studies' but in general, if using the spotmeter I would need to add 1/2 EXTRA EV to compensate. Say, spot metering on a white object, theory would recommend +2 EC and if it was, say a solid white wall, Matrix and center weighted would be fine. Spot meter would need an add boost of 1/2 stop to be equal.
05-23-2008, 07:59 PM   #34
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I don't want to come off as a condescending jerk here. But I have done this a couple of times so I thought I would just throw it out there as a possibility. It is not hard to hit the EV button below the rear e-dial while twirling the front e-dial and then forget that you did this, leading to many shots that are either over or under exposed. I now get into the habit of holding down the EV button and pushing the green button which resets the EV to the default. Probably nobody else is as ham-handed as me

05-24-2008, 12:27 AM   #35
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QuoteOriginally posted by danny09 Quote
Can you please post the link of the review which you mentioned?
Danny - the review is not on line yet - only in the paper mag.
05-24-2008, 02:42 AM   #36
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QuoteOriginally posted by jbinpg Quote
I don't want to come off as a condescending jerk here. But I have done this a couple of times so I thought I would just throw it out there as a possibility. It is not hard to hit the EV button below the rear e-dial while twirling the front e-dial and then forget that you did this, leading to many shots that are either over or under exposed. I now get into the habit of holding down the EV button and pushing the green button which resets the EV to the default. Probably nobody else is as ham-handed as me
I also had a problem with my K10D where the AE-L was going on by itself, with absolutely no input from my "finger". It took me a short while to figure out what was going on, so it might be a good idea to look at that.
05-29-2008, 08:31 PM   #37
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Code:
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You had Dynamic Range Expansion set to ON.

https://www.pentaxforums.com/forums/255924-post67.html

See my post with some tests involving EDR combined with RAW-only shooting. End result: EDR does nothing in RAW mode other than underexpose by one stop.

Unfortunately it is not documented in the manual that EDR is a JPEG-only function and will have negative effects if you shoot only RAW.
05-30-2008, 12:06 AM   #38
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This is a very interesting comment. I will disable that mode to see the difference.

However I was more or less considering picture 905 OK. Please have a look at 906 taken with spot meter on the same subject which is darker.

You will notice that most of the other pictures are taken with EDR = off. So it cannot explain all.

For instance 1109 / 1110 were taken with EDR = off and again it shows an underexposure in spot meter measure vs. multi-seg measure.

Thanks a lot.

P.S. I still have not got feed-back from Pentax support regarding this problem.

05-30-2008, 12:21 AM   #39
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I have a question regarding the shots, and while I agree with many posters who advise using manual settings and a trial shot, I have another possible issue.

Have you considered that your metering might be getting fooled by light entering the viewfinder?

You are in a desert situation with a lot of reflected light, not just the direct sunlight.

I wear glasses and I often wonder if occasionally the lack of shading of the view finder causes under exposure in bright conditions.

ps.

my K10D virtually lives in manual mode where I meer off the pavement to get a good indivation of incident light, and then just keep shooting until lighting changes.
05-30-2008, 06:18 AM   #40
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QuoteOriginally posted by Lowell Goudge Quote
Have you considered that your metering might be getting fooled by light entering the viewfinder?
mrechte answered to this question in post #29. Good point, though
05-30-2008, 07:51 AM   #41
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QuoteOriginally posted by Lowell Goudge Quote
... and while I agree with many posters who advise using manual settings and a trial shot,
...
my K10D virtually lives in manual mode where I meer off the pavement to get a good indivation of incident light, and then just keep shooting until lighting changes.
Well, your point confirms that the Kx0D series are not very good at light measuring.

I will not trust the K20D light meter anymore, and I start wondering whether I made the good choice with this camera...

If I was to re-program the firmware, I would increase exposure at least +0.5 IL on multi-seg and +1 IL on spot measures.

I have 2 friends who use respectively Nikon and Leica digital cameras who do not complain of exposure problem in auto mode (both of them have taken shots in the same environment, viz. desert scenes). Again I hope that my camera has got a malfunction, because I cannot accept the results I published along this thread. I do not wish to use Photo Laboratory to correct any single picture I have shot. Sorry if again I touch most of Pentax users on this site.
05-30-2008, 08:55 AM   #42
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QuoteOriginally posted by mrechte Quote
I will not trust the K20D light meter anymore, and I start wondering whether I made the good choice with this camera...
@mrechte, maybe, you find the following interesting.

I've recently read an article about spot metering in particular and that one should always do test shots in conjunction. The reason?

Well, it only looks at one spot (it's purpose) and will adjust the exposure as for a gray target (18% gray?). But you never really know how gray the spot really was (you may know for a caucasian face, but other than this...). So, a spot metering almost always is accompanied by EV compensation.

So, I went back to your photos and studied some of them with PhotoME (if you don't already use it -- get it!).

It will actually show all the matrix exposure readings in LV layered on top of the image. It also computes the effective LV which your image was taken at with.

What I found is that with spot metering, the effective LV the image was taken at was consistently about 1.1 LV higher than the spot reading.

So, probably ok and spot metering with a narrow spot is just tough to handle, actually. Personally, I don't use it as it doesn't work with split screens.

As for matrix metering. There is a common sense here that the Pentax tend to underexpose by about -0.5EV, but people normally consider this to be ok and more in line with the rule of the digital era to expose to the right.


But then, maybe your light metering is faulty, indeed.

To check this out, you could meter two face subjects (dark/bright), hand-meter both to know their LV (or spot meter them from close enough), take pictures, and control the matrix metering values via PhotoME.


UPDATE:
I had a look at your recent shots and the exposures can all be explained by spot measure +1.1EV.

Except the last one, IMGP0698.jpg:

This is a matrix exposure, the image is taken at effective exposure of 13.5LV, the matrix fields are all in between 12.0 and 13.0. So, the decision to take the image at 13.5LV is perfect.

Still, the histogram shows that the image is underexposed by a full 1EV. Like the original light values all ranged from 11.5 to 12.5.

Therefore, I am tend to believe that your unit's 16 exposure meters measure by 0.5 stops too low.

Last edited by falconeye; 05-30-2008 at 09:41 AM.
05-30-2008, 10:14 AM   #43
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Thanks for spending your time analyzing my pictures.

I followed your advice and installed the photoMe utility. It is amazing to see the amount of information stored within the picture (thanks my VISA # was not there).

I am not very clear with the Effective LV and Segment LV. I guess that the Effective LV is the value the firmware will choose for setting the physical parameters (aperture, ISO, speed), based on the segments LV and some Pentax magic ? If so why in spot measure the Effective LV is not the centre segment LV ?

QuoteQuote:
Still, the histogram shows that the image is underexposed by a full 1EV. Like the original light values all ranged from 11.5 to 12.5.
Where do you read this information ?
05-30-2008, 11:09 AM   #44
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I recently bought a k10d from the store and have been having exposure problems as well. Now I am totally new to the SLR field so maybe this camera really is too much for me, but I have tried all the metering methods on a single object and they all come out underexposed. The EV compensation is set to zero.

For this reason I am 90% sure I am going to take the k10d back today. I will probably end up getting the k200d even though I am sure I will miss the big view finder and the front dial. My noviceness might be better served with the scene modes as well.

So I agree with the OP about exposure problems.
05-30-2008, 11:59 AM   #45
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Two DSLR newbies find the same thing wrong with similar cameras. I'm starting to see a pattern.
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