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07-26-2010, 05:36 PM   #1
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K-7 Overexposes

I posted this in the Sigma 10-20 forum as well but I'm not sure if it's a lens or camera problem. I don't know it to be lens specific, although I have only noticed it using the mentioned lens. Recently I began noticing crazy overexposures when shooting at small apertures; the examples were shot at f16. This behavior isn't consistent. I have attached two images from a set of 15 photos I took Sunday, using identical settings on the lens and camera. The first 12 are so overexposed that I can't even recover the highlights, the last 3 are fairly well exposed. I am attaching the 12th and 15th of the series.

The attached images are all shot in with the K-7, RAW, Av Mode, ISO 100, Matrix Metering. The camera calculated a shutter speed of 1/80" for both images, which seems about right given the Sunny 16 rule but as you can see they are not even close.

Can anyone offer any suggestions?

Thanks in advance for any input.

OK, can't seem to get the images to attach...


Last edited by dhulsmeyer; 07-26-2010 at 05:40 PM. Reason: added photos
07-26-2010, 06:50 PM   #2
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You should check and see if your lens suffers from lazy aperture. Try to move the level by hand and see if it is snappy. My guess anyway.

Regards,

Peter
07-26-2010, 06:52 PM   #3
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I've noticed a higher risk of getting blown-out highlights with the K-7 when shooting wide angles 10-20mm and bright light. It happens with different lenses.
The K-7's dynamic range is a bit less than some of the competition, I suppose.

I don't really have complaints of overexposure, though, as the mid-tones are usually correctly exposed.

In a situation like that (wide angle, bright, contrasty scene), I normally dial down -1 E/V, then adjust the RAW file for shadows and mid-tones in PP.

Does your camera meter correctly in other situations ?
Exposure metering defects will normally show up in a wide range of situations regardless - wide-angle, telephoto, normal, bright light, dim light etc.
And, yes, it may be a lens aperture problem, especially if it has seen a lot of heavy usage.
07-26-2010, 07:26 PM   #4
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So many possible reasons:

- Using a third party focus screen and using spot metering
- Slow aperture blades
- Metering issue

07-26-2010, 11:34 PM   #5
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Yep, I've noticed that too with my K7 : in full sun, I have to dial -1ev to preserve the highlights.

And in shadow or under cloudy skies, it's the opposite...
07-27-2010, 01:53 AM   #6
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Yep.

...and when built-in flash are used to remove shadows in sunlight it sometimes have the shutter speed go down to 180/1 without compensating by changing aperture. Giving immense overexpose where EV -5.0 are not nearly enough.
Have to go all manual.
07-27-2010, 04:46 AM   #7
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QuoteOriginally posted by tiltman Quote
...and when built-in flash are used to remove shadows in sunlight it sometimes have the shutter speed go down to 180/1 without compensating by changing aperture. Giving immense overexpose where EV -5.0 are not nearly enough.
Have to go all manual.
In Av mode, I'd call this normal, except that, from memory, the speed does not blink like it used to on previous models, IIRC...

In other modes, I'd say it all depends on what program line you're on...
07-27-2010, 07:31 AM   #8
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QuoteOriginally posted by dlacouture Quote
In other modes, I'd say it all depends on what program line you're on...
I use "P" 99% of the time.

However, the overexpose-in-good-light-when-flash-up syndrome does not happen all the time but only occasionally. Two days ago I had 400+ images from a photo shoot in bright sunlight, flash used in approx half of them. 4 pictures was heavily overexposed. These four pics was taken in a row.

Note;
If I touch the back wheel when i P mode I might force overexpose in bright light when flash opens because the camera set a max shutter speed of 180 and can't adjust the aperture accordingly (due to my wheel actions).
I'm pretty sure this scenario is not what happens here. I have so far detected the overexposing way too late, I have to detect it when it happens.

Note 2:
I do not remember any blinking of the exposure time at any time.

Edit:
(You are right: ) Just tested, the K7 in P mode don't blink the exposure time when forced to overexpose (manual 2.8f in daylight and then open flash). K10 do blink the line below aperture setting.


Last edited by tiltman; 07-27-2010 at 07:47 AM.
07-27-2010, 09:07 AM   #9
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Without images and exif data, one can only speculate, but keep in mind your camera meter expects the scenes it "sees" to average out to 18% grey. You have to know when and how to override the meter.
07-27-2010, 09:37 AM   #10
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QuoteOriginally posted by dlacouture Quote
Yep, I've noticed that too with my K7 : in full sun, I have to dial -1ev to preserve the highlights.

And in shadow or under cloudy skies, it's the opposite...
This is pretty much my experience, and my accommodation.
07-27-2010, 10:12 AM   #11
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You can go into the menu and select the D-Range option. You can enable Highlight and Shadow correction. You'll be shooting at ISO200 after that as the lowest. It helps and you can also use the Main Switch to "snap" a preview shot that will show a histogram and highlight on the screen blown highlights and shadows. You then can adjust the EV compensation to taste.

Note on a bright, sunny day there is WAY more light than can be captured in a single shot on any camera (scene dependent). And small APS-C sensor cameras have even a tougher time. So you need to make a decision often. Bring in the highlights at the expense of shadows, the opposite, find the best balance of losing both or take several shots at different exposures and combine into one. Graduated ND filters help too but can't be applied to every scene all the time.

Last edited by tuco; 07-27-2010 at 10:21 AM.
07-27-2010, 11:40 AM   #12
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QuoteOriginally posted by tiltman Quote
I use "P" 99% of the time.

However, the overexpose-in-good-light-when-flash-up syndrome does not happen all the time but only occasionally. Two days ago I had 400+ images from a photo shoot in bright sunlight, flash used in approx half of them. 4 pictures was heavily overexposed. These four pics was taken in a row.
Well, if you are in Matrix metering mode, I'd say it's possible, as the camera will then make wild assumptions about what you are trying to do, and sometimes really bloarfs things totally... The more so if the four shots were of the same scene...
If not, then it could also be something you set accidentally..

QuoteOriginally posted by tiltman Quote
(You are right: ) Just tested, the K7 in P mode don't blink the exposure time when forced to overexpose (manual 2.8f in daylight and then open flash). K10 do blink the line below aperture setting.
Yep, that's a real PITA, as this means there is currently no way on the K7 to know if you're overexposing the ambient with the flash extended...
07-28-2010, 02:27 AM   #13
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QuoteOriginally posted by tiltman Quote
Yep.

...and when built-in flash are used to remove shadows in sunlight it sometimes have the shutter speed go down to 180/1 without compensating by changing aperture. Giving immense overexpose where EV -5.0 are not nearly enough.
Have to go all manual.
Why don't you use HSS on the flash? Then shutter speed is not limited to 1/180 (although the distance the flash can cover decreases a lot, so you subject cannot be too far away).
07-28-2010, 05:37 AM   #14
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QuoteOriginally posted by simico Quote
Why don't you use HSS on the flash? Then shutter speed is not limited to 1/180 (although the distance the flash can cover decreases a lot, so you subject cannot be too far away).
The built-in flash can't do HSS.
07-28-2010, 06:13 AM   #15
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QuoteOriginally posted by dlacouture Quote
Yep, that's a real PITA, as this means there is currently no way on the K7 to know if you're overexposing the ambient with the flash extended...
Agreed.

I went back and study the EXIF of the overexposed images. They all (the four mentioned above and another two from a earlier session) was marked with "Av" mode.

This indicates "P" mode on camera and that I somehow have touched the back wheel before using the built-in flash. Strange, but still a reasonable explanation.

QuoteOriginally posted by simico Quote
Why don't you use HSS on the flash? Then shutter speed is not limited to 1/180 (although the distance the flash can cover decreases a lot, so you subject cannot be too far away).
High speed with the built-in flash ?
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