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02-16-2012, 11:33 AM   #1
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Overexposure on snow

HI!
I am happy owner of K-5 for 3 monts.
But now I've noticed that when shooting on the snow heavily overexposes. I do not use any exposure compensation, using standard settings, AE Point is not linked to the AF, using multisegment metering. Photo on the snow is just OK, but when the shot contains a strip of forest, exposure is rapidly increasing. Sometimes just a shift of 5% of the image and already image is shifted by 1 or more Ev. Metering in normal conditions, gray table, comparing with flash/luxmeter is OK. Itīs not coincidence, i have a lot of such photos.
I am confused...i have to check histogram/overburns after taking every shot. But often i have no possibility to check it immediately and i find such unusable photos after arriving to home.
I am an experienced user of SLR (MZ-5n analog) and I never noticed such problems.


Attachments: first pic is overexposed (1/250 F5.6) and second pic is appropriate (1/320 7.1)it is exactly 1Ev darker).
I have more such photos for examination. And much more overexposed..

Attached Images
View Picture EXIF
PENTAX K-5  Photo 
View Picture EXIF
PENTAX K-5  Photo     
02-16-2012, 12:03 PM   #2
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That is to be expected since you have set the camera to spot metering (unless you are trying to focus on the snow); try center-weigh metering. The AE not linked to AF option only applies when you use matrix metering.
02-16-2012, 12:11 PM   #3
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QuoteOriginally posted by kluvi Quote
HI!
I am happy owner of K-5 for 3 monts.
But now I've noticed that when shooting on the snow heavily overexposes. I do not use any exposure compensation, using standard settings, AE Point is not linked to the AF, using multisegment metering. Photo on the snow is just OK, but when the shot contains a strip of forest, exposure is rapidly increasing. Sometimes just a shift of 5% of the image and already image is shifted by 1 or more Ev. Metering in normal conditions, gray table, comparing with flash/luxmeter is OK. Itīs not coincidence, i have a lot of such photos.
I am confused...i have to check histogram/overburns after taking every shot. But often i have no possibility to check it immediately and i find such unusable photos after arriving to home.
I am an experienced user of SLR (MZ-5n analog) and I never noticed such problems.


Attachments: first pic is overexposed (1/250 F5.6) and second pic is appropriate (1/320 7.1)it is exactly 1Ev darker).
I have more such photos for examination. And much more overexposed..
You got more range in the pictures between the forest and the snow than the sensor can handle. That is an excessively contrasting scene.
You can sometimes help them after the fact with photoshop but.....

My suggestionis to set the exposure meter to 'spot meter' as trying to find the right exposure for the whole frame when that is a mission impossible
doesn't work. Also recompose the photo--- with a different lens or in a different location to reduce the contrast of the scene. But I use spot metering mode a lot to avoid baffling the sensor with a mission impossible and resulting irratic results.

On edit: I think the two messages here are NOT contradictory. but get the camera off the 'green mode' if its there
(program mode is fine), and move the lever under the exposure mode dial off the green position to either center weighted
or spot metering....

Last edited by rvannatta; 02-16-2012 at 12:35 PM.
02-16-2012, 12:19 PM   #4
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QuoteOriginally posted by aleonx3 Quote
That is to be expected since you have set the camera to spot metering (unless you are trying to focus on the snow); try center-weigh metering. The AE not linked to AF option only applies when you use matrix metering.
As you can see on attached pics with EXIF...there is MULTI... (exif directly from uploaded pics may be corrupted)

02-16-2012, 12:25 PM   #5
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QuoteOriginally posted by rvannatta Quote
You got more range in the pictures between the forest and the snow than the sensor can handle. That is an excessively contrasting scene.
You can sometimes help them after the fact with photoshop but.....

My suggestionis to set the exposure meter to 'spot meter' as trying to find the right exposure for the whole frame when that is a mission impossible
doesn't work. Also recompose the photo--- with a different lens or in a different location to reduce the contrast of the scene. But I use spot metering mode a lot to avoid baffling the sensor with a mission impossible and resulting irratic results.
OK your are right. But my old MZ5n handled it OK :-) I expected that it will try to avoid burnouts...they are more dangerous...
I am not sure if it isn't problem of my camera... ... or Is it the way how the Pentax sees the progress?
02-16-2012, 12:39 PM   #6
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I've read several posts indicating that film was a lot more forgiving of excessive dynamic range than digital. The K5 sensor has a large 14+ ev range, but only at 80 iso. As one goes up in iso, that ev range decreases quite rapidly. The DXO site has the charts i believe. A lot of the digital progress has been aimed at solving that problem.
02-16-2012, 12:40 PM   #7
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Why not set camera to manual exposure, set to spot metering, meter off the snow to +2EV, then focus and shoot?
You have plety of headroom with the K-5 to pull out the shadows.
02-16-2012, 12:51 PM   #8
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photos has been taken by ISO100 (around 12.4Ev or so).
And i used reversible film on my MZ5n....with only occasional problems..
:-(
I think that it is caused by "too smart" AE multisegment metering.
I used +2/3Ev on ma analog... and now in most cases on snow 0Ev, but sometimes it is fooled and -1Ev is not enough...
Probably i have to forget "shoot and forget" method on snow even when i do not require excellent results (eg snapshots to my mom's family album).
Funny is that my 10yrs old bumpy compact (100USD in 2002 ) have no such problems...

02-16-2012, 12:55 PM   #9
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yes...when you have time enough.....but sometime you have no time to fiddle with camera... for instance snapshots.
And sometime you are lazy to fiddle with it...you only want to make regular photo, not excellent one. I am propably spoiled from my analog and stupid digital camera.
02-16-2012, 01:26 PM   #10
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Sorry, I misread how you meter on that particular shot. As other posters suggested, that is a high contrast composed shot you have, and matrix metering is likely not the best case scenario for a shot that you intended to. If you had zoomed in your shot (without the dark forest background) the camera metering (multi-segment) would have been different. In this case, the camera is doing the best under that circumstances.
02-16-2012, 01:31 PM - 1 Like   #11
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from what i can gather, you're doing multi segment metering in a high-contrast area and you are shooting in JPEG mode as well.
Here's where things are going wrong:
1. multisegment metering is reading the whole scene, sees it as a high-contrast scene and tries to make everything 18% grey. Theres a big white thing and a big black thing in the scene, so multisegment metering + using a semi-auto mode will result in inconsistent and possibly inaccurate exposures. There's just simply more dynamic range than what the camera can deal with and it's trying to find the best compromise of blowing whites and blacks.
2. you're shooting jpeg. This kills the massive dynamic range benefits of shooting with the k-5 since you're giving up massive amounts of raw data that would usually let you recover the lost dynamic range. Furthermore, you have both shadow recovery and highlight recovery turned off, meaning that the jpeg processor won't even really try to fit more dynamic range into the image. also, your jpeg processor has contrast level set to 1, which further decreases the amount of dynamic range you get. In such a high-contrast scene, even if you hit proper exposure, you're giving up a ton of dynamic range.

with that being said, your properly exposure image looks underexposed by at least half a stop IMO and your overexposed scene, despite blowing highlights, looks a lot more properly exposed to me.
02-16-2012, 01:50 PM - 1 Like   #12
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QuoteOriginally posted by adpo Quote

with that being said, your properly exposure image looks underexposed by at least half a stop IMO and your overexposed scene, despite blowing highlights, looks a lot more properly exposed to me.
I agree with your comment, the top photo is how I would expose for snow. Snow is in reality dazzlingly bright and for that reason, even the human eye will lose detail. Lowering the EV to get maximum snow detail produces in my opinion an unnatural image, which is fine if that's what you are aiming for but in that case you'd have to adjust the exposure accordingly and not rely on the camera to do it.

That's my take on it anyway.
02-16-2012, 01:59 PM   #13
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The K5 matrix metering, unfortunately, is not reliable, probably this is caused also the flash overexposure. Try to center-weighted metering always!
02-16-2012, 03:28 PM   #14
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Thanks for all your opinions and advices.
TO aleonx3: eyes it would be different. If there is more of forest then it will be more overexposed. I made some test sheet and accordance to those two photos very small difference in forest area leads to great difference in (over)exposition.

TO adpo:ad 1): if i would be Multisegment Meter i would be much smarter ....
2)Yes you are right (shadow & highlight recovery), i tried to switch to NATURAL color (and contrast) profile but with the same results. But i am lazy to switch a lot of parameters every time when i have to use camera. And lazy to process every photo in photo and RAW editor (when i do not require perfect quality). And i always forget to switch some important parameter back to usual and proper value. :-D
"with that being said...." strange...i will think about it... and i can add some noise to blowed lights...(but i still have to use the editor...)

TO Bredoteau: yes i agree
I thought that the multisegment measurement was developed mainly for such cases. It seems that center-weighted metering would be better and first of all more predictable. When i think about it....i am not able to imagine me the reason (and conditions) why to use THAT multisegment metering ....
Thank You gentlemans.
02-16-2012, 05:27 PM   #15
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QuoteOriginally posted by kluvi Quote
photos has been taken by ISO100 (around 12.4Ev or so).
And i used reversible film on my MZ5n....with only occasional problems..
:-(
I think that it is caused by "too smart" AE multisegment metering.
I used +2/3Ev on ma analog... and now in most cases on snow 0Ev, but sometimes it is fooled and -1Ev is not enough...
Probably i have to forget "shoot and forget" method on snow even when i do not require excellent results (eg snapshots to my mom's family album).
Funny is that my 10yrs old bumpy compact (100USD in 2002 ) have no such problems...
Negative film is very forgiving to shoot. A lot of sins could be hidden in developing and printing.

Digital is like slide film, once you clip the highlights, they are gone. If you lose the highlights, you cannot recover them.

For what it's worth, your first picture is not overexposed on the snow. The snow is white, exactly as you'd expect, not grey like a meter would try to make it.
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