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05-13-2007, 08:00 PM   #1
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Exposure Comp. Question

I have both a Ds and a K10. The Ds requires no EV compensation but the K10 is very under exposed without a comp of +1.5 regardless of the camera's other settings. A variety of AF and A lenses were tested on both cameras in the P mode using the same subjects at the same time both indoors and outdoors in bright sunlight. The K10 has an attached grip and the ISO on both cameras is set to auto.

Is there a problem with the K10 or is it usual or common for it to under expose without compensation? I'm still learning the camera's features after a few months of ownership but just discovered EV issue with it. Could I have overlooked something?

Any ideas or suggestions would be greatly appreciated.

John

05-13-2007, 08:08 PM   #2
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QuoteOriginally posted by JohnV3 Quote
... the K10 is very under exposed without a comp of +1.5 regardless of the camera's other settings. ...

Is there a problem with the K10 or is it usual or common for it to under expose without compensation?
Have you installed the latest firmware update (1.2)? I am pretty sure someone here noticed that, after installation, his exposures needed less compensation than before. I think I saw the same thing, but I'm not sure.

Will
05-13-2007, 08:15 PM   #3
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Will,

Thanks for your quick response. No, I haven't upgraded to the latest version since I'm not into remote assistance at this time. I'm using ver 1.11.

John
05-13-2007, 09:43 PM   #4
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QuoteOriginally posted by JohnV3 Quote
Thanks for your quick response. No, I haven't upgraded to the latest version since I'm not into remote assistance at this time. I'm using ver 1.11.
It is always a good idea to update to the latest firmware if you experience problems. If you have no issues with the camera, I would say the firmware upgrade is optional.

All firmware upgrades include many tweaks or minor updates which are not mentioned in the list. So the v1.2 is more than just the remote assistance.

05-13-2007, 10:59 PM   #5
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QuoteOriginally posted by JohnV3 Quote
Is there a problem with the K10 or is it usual or common for it to under expose without compensation? I'm still learning the camera's features after a few months of ownership but just discovered EV issue with it. Could I have overlooked something?
I am a fairly new user like yourself and also (possibly like yourself) mostly experimenting right now while getting familiar with the controls, options, settings, etc so I don't have to fumble around when I want to select a particular setup. I'm a little behind you as I've only had the camera a couple of weeks.

With that in mind, and my limited experience with the camera, my impression is my K10D underexposes slightly, no matter what mode I am using (although I have very limited experimentation with some of the modes and none with manual.

I am thinking of starting to experiment with EV values in the next couple of days to see if I can nail it down one way or another, detect any trends, etc.

And yes, I do have the latest firmware onboard.
05-14-2007, 01:56 AM   #6
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Contact Pentax, report the problem and request for their rectification.

If they don't acknowledge the problem and try to persuade you that "it's normal", you should believe yourself and insist for a repair. To prove, ask Pentax to have another k10d to compare with, or, bring your DS to show the difference and the (obvious) underexposure.

p.s. I have heard so many and too many stories over years (and my true personal experience as well) that Pentax servicing have been rather unhelpful and they often tried to avoid reported problems. YMMV, though. At least you should try, I think.

QuoteOriginally posted by JohnV3 Quote
I have both a Ds and a K10. The Ds requires no EV compensation but the K10 is very under exposed without a comp of +1.5 regardless of the camera's other settings. A variety of AF and A lenses were tested on both cameras in the P mode using the same subjects at the same time both indoors and outdoors in bright sunlight. The K10 has an attached grip and the ISO on both cameras is set to auto.

Is there a problem with the K10 or is it usual or common for it to under expose without compensation? I'm still learning the camera's features after a few months of ownership but just discovered EV issue with it. Could I have overlooked something?

Any ideas or suggestions would be greatly appreciated.

John
05-14-2007, 02:09 AM   #7
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Interesting John. I have just the opposite situation. My DS habitually under exposes, and the K10 is usually spot on.

A couple of questions and suggestions.
1.What metering mode are you using?

2.Take the ISO off automatic and set to 200 or 400 for comparison sake.

3.Retest using all common metering modes P,AV,TV.

4. Are the results consistent across all modes?
05-14-2007, 04:51 AM   #8
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questions, questions, questions.....

I have a lot of questions about your post.

have you looked at the histograms for the exposures. how do they appear.?

are you judging this by the camera display only?

what are your metering settings? Spot, center weighted, multi segment?

While I don't disagree that latest software is always a good idea, V1.2 should not change anything in this respect.

the only thing I have found is that the center spot metering is very precise, and can give misleading exposure if you point it at the wrong thing.

05-14-2007, 06:42 AM   #9
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QuoteOriginally posted by JohnV3 Quote
I have both a Ds and a K10. The Ds requires no EV compensation but the K10 is very under exposed without a comp of +1.5 regardless of the camera's other settings. A variety of AF and A lenses were tested on both cameras in the P mode using the same subjects at the same time both indoors and outdoors in bright sunlight. The K10 has an attached grip and the ISO on both cameras is set to auto.

Is there a problem with the K10 or is it usual or common for it to under expose without compensation? I'm still learning the camera's features after a few months of ownership but just discovered EV issue with it. Could I have overlooked something?

Any ideas or suggestions would be greatly appreciated.

John
Just do a "white wall test" to see your meter basline. For the sake of avoiding any arguements I list everything as "probable" and subject to a bit of variation. My
belief is most of the K series will "baseline" around 110-126...
The "off" measurement is the D series which was calibrated to a low baseline 90-110 generally speaking. Use center weighted to avoid matrix complications though it should not matter much w/ a white wall. Spot metering has a tendency to be 1/2 stop lower..for whatever reason. Test both cameras and post results. Any solid color object (no-reflective of course ie high gloss) will do. Best to be close w/ WB though to be more accurate.
Test both cameras. Based on the below theory the DS should always expose a tad darker (they were calibrated to the lower D standard but may have been tweaked up a half of stop so 90-110 is the possible norm) than the K. Your DS could be out and the K fine. Either way this will help you to determine what is going on. Make sure Exp comp is off as well.


Last edited by jeffkrol; 05-14-2007 at 06:48 AM.
05-14-2007, 06:59 AM   #10
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I just want to add that on my K10D the picture appears to be overexposed, or certainly very bright when view on the LCD monitor (on cam). But when I get it on to my computer, and view it on that monitor/prints the image, the exposure is usually spot on.

I had a bad day with this, checking the images on the LCD, figuring they were overexposed (Didn't look at the histogram), and compensated for the imagined overexposure.

Ended up underexposing 60-70 images.

Now, I've learned to trust my K10D. If it says the exposure is fine, then most likely it is.

Regards,
Beej80
05-14-2007, 10:32 AM   #11
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Thanks everyone for your replies and suggestions. To answer a few questions:

My testing was only done in the P mode.

The underexposure was confirmed by viewing the photos on the computer monitor (19" screen). It is also apparent in the LCD screen which is of little value with the bright Arizona daylight unless you view it in a dark room.

I've tested with both center weighted and multi segment metereing. It made no difference. I have done a white wall test indoors and the results were the same.

I haven't viewed the histograms but the colors look good after just brightening in an editing program. It takes very liitle eyeball scrutinizing to determine the under exposure.

I will do further testing, as suggested, using a fixed ISO and other metering modes. If there is no difference noted, I will upgrade the firmware to 2.0. I will also call Pentax support but done expect much help or knowledge from call centers.

Thanks again everone. I will report back the resilts of further testing.

John
05-14-2007, 11:56 AM   #12
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QuoteOriginally posted by JohnV3 Quote
Thanks everyone for your replies and suggestions. To answer a few questions:

I have done a white wall test indoors and the results were the same.

I haven't viewed the histograms but the colors look good after just brightening in an editing program. .

John
Sorry, what were the mean/median on the ww tests??? Don't use auto in any editor. your results will help (me at least
05-14-2007, 12:41 PM   #13
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Jeff:

The wall test was simply an eyeball test for exposure differences. No measurements were taken. Sorry, but I'm not advanced enough to really understand the histogram test especially where the histogram window that you have shown is found (what program or application?) and what the numerical results would mean.

John
05-14-2007, 01:00 PM   #14
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The histogram window can be found in photoshop under window/histogram (at least on a PC with photoshop version CS2.)

I tried it with my K10 and it comes out with fairly low numbers compared to your chart.

Results from 2 shots of a white A4 paper, multisegment metering.

Mean/median the whole picture.
93/94
94/95

Mean/median in center of picture (obviously heavy vignetting with kit zoom)
106/108
106/108

Itís quite common that I add 0.5-1 EV without blowing the highlights, but in the end it turns out just fine.
05-14-2007, 01:50 PM   #15
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I found the histogram in PS7 under Image menu but it measures RG&B independently along with luminosity instead of what is shown above. It is now on my list of tests to do.
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