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03-25-2009, 08:20 AM   #16
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I think the 6400 ISO setting is in orange for a reason: it's really pushing the envelope, and it's an option to use carefully. I can get some pretty neat results in monochrome with it, but it's chancy, (At least till I'm a better hand at post-processing) and often better on balance to go with 3200, where I think the K20d performs pretty favorably compared to my friend's d300, actually. (In monochrome, at least)

Frankly, the high-ISO performance is more than I hoped for: and Jewel's very right about the NR scheme, which I find serves me pretty well. I kind of hope Pentax comes up with some real turbo high-ISO performance in the future, like the D3 could boast, but for all practical purposes, 3200 ISO is enough for most jobs. (I just love low-light shooting, so I can see plenty of uses for really crazy ISOs.

03-25-2009, 09:06 AM   #17
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QuoteQuote:
dlacouture I think nobody here actually read the original post : Henkezd's problem is not with chroma or luminance noises, but with broad blue/purple coloration of the pics occuring near the top and bottom borders... I have the same problem on my k20.
I carefully read the OP. Trouble I had with it, was the Utube video did not have enough resolution for me to see the problem. Sure, at 3200 & 6400 ISO a color cast is evident, but there is absolutely no EXIF data given. The video does not show me any noise problems--for that, some actual, %100 crops with EXIF is in order, as well as a better, in depth description of the actual concern.

BTW the title the poster gives tot his thread is:

K20d NOISE?
03-25-2009, 09:14 AM   #18
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dlacouture: I have the same problem on my k20
Can you post some actual pics, with EXIF data, for us to look at so we can help? Can you spend a little more time with a description of the problem? I understand, since you are familiar with the issue, you immediately and naturally connect to the OP's problem. For those of us without the problem, however, the OP's original post needs better development.

I am not saying there is not a problem with the issue at hand. I am just saying I need a better description and presentation of it. Can you help? Thanks.
03-25-2009, 09:24 AM   #19
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Lol101: Excellent!! I too am a big fan of not forcing NR on users by default and giving them the choice!

... except it has almost nothing to do with the OP's problem... which looks like some color shift at higher ISO
Precisely, it "looks like some color shift at a higher ISO. This is my point. But the Utube video the OP provides does not have any EXIF data with it. Not only that, the video is lacking in resolution. Also, the OP titled the thread K20D NOISE? I think the question mark by the OP is significant--he is asking if the problem is noise related, though given the OP's comment here: "Sorry for my english btw, hope you understand me anyway" it is hard to be certain.

The color cast seen in the video may be as simple as a white balance problem, incorrect exposure, or combination thereof. We are not given much to go on. I am hoping to get more from those who are articulating the problem.

BTW, thanks for the complement.

03-25-2009, 11:18 AM   #20
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Jewelltrail: Sure, here we go...


This was shot RAW at 6400 iso, f/2.8, 1/640, AWB (but WB obviously has no effect here!), with the cap on, then developped in-camera with a +2Ev setting (to emphasize the problem)...
I tried at various speed, and the results are quite constant, at 1/4000 or 30"...

So far, that's my only gripe with my k20, as this ruins my shots above 3200 iso... Otherwise, noise would be quite good above 3200...
03-25-2009, 11:55 AM   #21
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Wow :O I got many more replies than I expected :P

It's like dlacouture said, the blue cast that's my problem, I've tested a bit more in different lightning conditions, daylight WB gives the noise a red tone, lightbulb makes it blue. It's much more hard to see in daylight, but it's there, making the image lighter in the borders which annoys me, I haven't seen anything like this on any other camera.
When I search on flickr.com for "K20d iso 6400" nearly all of them are free from this noise problem from what I can see, i've seen it somewhere else were other people have the same problem.

If this is how k20d are supposed to act then I'll try to get rid of it as fast as possible, I must be able to take photo at iso 1600 without having a light colorued edges ! :ugh:

EDIT: Some samples with exif
http://lillehem.eu/k20dnoise/IMGG-3.jpg
http://lillehem.eu/k20dnoise/IMGG-4.jpg
http://lillehem.eu/k20dnoise/IMGG-5.jpg
http://lillehem.eu/k20dnoise/IMGG-6.jpg
http://lillehem.eu/k20dnoise/IMGG-7.jpg
http://lillehem.eu/k20dnoise/IMGG-8.jpg
http://lillehem.eu/k20dnoise/IMGG-9.jpg

Last edited by Henkezd; 03-25-2009 at 12:02 PM.
03-25-2009, 12:47 PM   #22
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QuoteOriginally posted by dlacouture Quote
This was shot RAW at 6400 iso, f/2.8, 1/640, AWB (but WB obviously has no effect here!), with the cap on, then developped in-camera with a +2Ev setting (to emphasize the problem)...
I believe that is called "amp noise". Looks like a different problem to me unless you're seeing this your normal pictures. Other cameras have this as well (google it).
The OP has a weirder issue IMHO. I'd exchange the body if I were him...
03-25-2009, 07:05 PM   #23
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Just a wild guess here.. have you tried this with a different lens? I'm just wondering if some imperfection in the lens (or coating) could cause that tint at those extreme ISO settings.

I've shot a bunch at ISO3200 and never saw this issue. I haven't done much at 6400 but maybe I'll shoot a few frames and see what happens



John

03-25-2009, 08:21 PM   #24
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QuoteOriginally posted by Henkezd Quote
Wow :O I got many more replies than I expected :P

It's like dlacouture said, the blue cast that's my problem, I've tested a bit more in different lightning conditions, daylight WB gives the noise a red tone, lightbulb makes it blue. It's much more hard to see in daylight, but it's there, making the image lighter in the borders which annoys me, I haven't seen anything like this on any other camera.
When I search on flickr.com for "K20d iso 6400" nearly all of them are free from this noise problem from what I can see, i've seen it somewhere else were other people have the same problem.

If this is how k20d are supposed to act then I'll try to get rid of it as fast as possible, I must be able to take photo at iso 1600 without having a light colorued edges ! :ugh:

EDIT: Some samples with exif
http://lillehem.eu/k20dnoise/IMGG-3.jpg
http://lillehem.eu/k20dnoise/IMGG-4.jpg
http://lillehem.eu/k20dnoise/IMGG-5.jpg
http://lillehem.eu/k20dnoise/IMGG-6.jpg
http://lillehem.eu/k20dnoise/IMGG-7.jpg
http://lillehem.eu/k20dnoise/IMGG-8.jpg
http://lillehem.eu/k20dnoise/IMGG-9.jpg
To be honest reading and looking I saw no problems and thought you where being too demanding with respect to iso6400 performance, but...

I agree with what you are seeing as being a problem I tried to reproduce it with my K20, going so far as to putting on my 50mm f1.7 so I could shoot at a wide aperture as you did on the dumbbell weights. I see your pics have a noise problem that I just don't see in any of mine. I do see color casts going over iso3200 from my K20D which is normal, but not what you refer or are showing. If this happens with all lights and different lens, send it back to Pentax showing the pic of the dumbbell weights at iso3200 with a 100% crop to aid them in seeing what you are talking about, and replies saying you do have a problem to help prove you case.

My K20D does loss some color accuracy and gains noise at iso3200, but its a fine grain noise and there is no color pattern noise as in your case (the blue dots in dark areas) your K20D seems to suffer some type of color noise in dark areas at higher iso's, 'Not' normal for the K20D.
03-25-2009, 11:12 PM   #25
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QuoteQuote:
Henkezd Wow :O I got many more replies than I expected :P

It's like dlacouture said, the blue cast that's my problem, I've tested a bit more in different lightning conditions, daylight WB gives the noise a red tone, lightbulb makes it blue. It's much more hard to see in daylight, but it's there, making the image lighter in the borders which annoys me, I haven't seen anything like this on any other camera.
When I search on flickr.com for "K20d iso 6400" nearly all of them are free from this noise problem from what I can see, i've seen it somewhere else were other people have the same problem.

If this is how k20d are supposed to act then I'll try to get rid of it as fast as possible, I must be able to take photo at iso 1600 without having a light colorued edges !

EDIT: Some samples with exif
http://lillehem.eu/k20dnoise/IMGG-3.jpg
http://lillehem.eu/k20dnoise/IMGG-4.jpg
http://lillehem.eu/k20dnoise/IMGG-5.jpg
http://lillehem.eu/k20dnoise/IMGG-6.jpg
http://lillehem.eu/k20dnoise/IMGG-7.jpg
http://lillehem.eu/k20dnoise/IMGG-8.jpg
http://lillehem.eu/k20dnoise/IMGG-9.jpg
Thank you very much for these pics. I have no technical expertise, only some real-life shooting with the K20 at higher ISO. But I do not shoot @ 3200 & 6400 often.

Note* it is immensely helpful, in a careful examination like this, to use a picture viewer which allows you to immediately scroll from one pic to the next, with EXIF data and histograms displayed for immediate comparison & evaluation.

That said, when I have shot high ISOs I learned how vital it is to expose to the right as far as possible. When I underexpose, at any ISO for that matter, noise begins to rear its ugly head. It is clear, using the histogram tool, that every shot you present here is underexposed. Note that img9 is your most exposed to the right shot you have.

Compare img8 to img9 for a sec, both of which were shot @ ISO 6400. Img8 has the horrible blue cast to which you refer, but img9 is mostly absent of the cast. What is different about them? Look @ their respective histograms for a sec and you'll see img 9 is closer to the right (though could/should be more so) than img8. Not a lot closer is img9 than img 8 to the right--which demonstrates how even a small difference in exposing can make all the difference when at extreme ISO limits.

Unfortunately, you do not provide a similar composition for img7, at a different exposure, which is also shot @ ISO 6400. However, img7, particularly when you see how horribly underexposed it is with a histogram tool, is a very good shot for ISO 6400. I am willing to bet, if you took the same shot, exposed to the right, this blue cast would be gone. You are shooting at the camera's most extreme limitations, and underexposing to boot. I am pretty sure I could produce similar casting problems with my K20 if I too shot in such low light, with such underexposed images. I could go try it, but it has been a long day/night. :ugh:

Img3, while still underexposed @ 6400, is more to the right than all but img9 and it shows; the image is not as bad as those where the underexposure is more severe.

I could go into more depth, but hope to have made my point. There is here, what social scientists refer to as a significant, negative correlation ie., the lesser the exposure, the greater the problem. I honestly believe this, but am surely open to the explanations of others. I could produce a nice ISO 3200 or 6400 shot with my K20, but I assure you accompanying those nice shots will be histograms which are exposed to the right!

Img4 is a horrible example I think because you have the extremes of darkness on one hand, with bright lights on the other. You exposed for the lights, and so the dark areas are tremendously underexposed. You simply cannot get away with underexposure at a camera's limits. Bear in mind that ISO 6400, on the K20, is only there for emergencies--by all accounts.

Finally, to sign off, look at your img5. It is shot @ ISO 100, ISO 100! And yet it has way too much noise in it. Why, well look at the tell-tale histogram--it is underexposed, by a lot--it is only exceeded in underexposure by img6, which you shot @ ISO 1600. It is a wonder img6 looks as good as it does--the noise, given the EXIF data, is not that bad.

Show me a great high ISO shot and I'll show you a great exposure--particularly indoors, in low light.

Last edited by Jewelltrail; 03-26-2009 at 12:30 AM.
03-25-2009, 11:13 PM   #26
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QuoteQuote:
dlacouture: This was shot RAW at 6400 iso, f/2.8, 1/640, AWB (but WB obviously has no effect here!), with the cap on, then developped in-camera with a +2Ev setting (to emphasize the problem)...
I tried at various speed, and the results are quite constant, at 1/4000 or 30"...

So far, that's my only gripe with my k20, as this ruins my shots above 3200 iso... Otherwise, noise would be quite good above 3200...

Thanks for this shot. Is it possible for you to provide real life pics?
03-26-2009, 12:18 AM   #27
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QuoteOriginally posted by palmor Quote
Just a wild guess here.. have you tried this with a different lens? I'm just wondering if some imperfection in the lens (or coating) could cause that tint at those extreme ISO settings.
Hi, the lenses I've used are Sigma Ex 24-70/2.8 and 50/1.4 for these tests and I experience the same problem with both, I've also seen it with an old m42 lens I hade mounted some months ago so I don't think it's lens related.

Found one other example of the color cast, which on this picture is a bit purple/red
http://lillehem.eu/k20dnoise/IMGG-1.jpg

Thanks for all replies, it's going back for a second service today...
03-26-2009, 12:52 AM   #28
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Couldn't pass on this one, so I did some quick shooting at 6400, trying to deliberately provoke color casting in my K20. I was not able to generate color casts like you are experiencing, though, when I underexposed, I surely got some small, blotchy blue areas. I just did not get the massive color casts which you have. I did not spend a lot of time, but enough where I feel I stand corrected; I would send the camera back for inspection. Best of luck to you.

Please report back here on how you make out--thanks.
03-26-2009, 02:46 AM   #29
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the K20D's behaviour in the high ISO's is well known. but they had to allow ISO 3200-6400 like the competition...


pentax's approach to removing noise is sublime, while lacking allmost entirely. they prefer heavy noise while keeping more detail. this kinda defeats the purpose, unless what you're actually looking for are noisy images.

sony's approach to noise is quite the oposite, kill the infidel )

pentax has proven over time that they cant do in-camera processing, just can't.

oversharpened jpegs, saturated, bad color casts, ocasional artefacts. so they decided they will just leave it up to the user's skill in postprocessing to try and make something of the image. (see the example above, with a 3 step algorithm to noise reduction )



i had a pentax, quite noisy. i also had a K10D for a basketball game and used ISO1600. it had alot of detail left mixed together with alot of noise. after resize and attempts to reduce the noisy look of the image, all i ended up with was some structured mush that someone was quoting above.

in the same light i used similarly priced nikon with ISO1600 and after the PP i had a better result overall.

peace.

Last edited by nicolaie; 03-26-2009 at 02:52 AM.
03-26-2009, 06:11 AM   #30
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QuoteOriginally posted by Henkezd Quote
Wow :O I got many more replies than I expected :P

It's like dlacouture said, the blue cast that's my problem, I've tested a bit more in different lightning conditions, daylight WB gives the noise a red tone, lightbulb makes it blue. It's much more hard to see in daylight, but it's there, making the image lighter in the borders which annoys me, I haven't seen anything like this on any other camera.
When I search on flickr.com for "K20d iso 6400" nearly all of them are free from this noise problem from what I can see, i've seen it somewhere else were other people have the same problem.

If this is how k20d are supposed to act then I'll try to get rid of it as fast as possible, I must be able to take photo at iso 1600 without having a light colorued edges ! :ugh:

EDIT: Some samples with exif
http://lillehem.eu/k20dnoise/IMGG-3.jpg
http://lillehem.eu/k20dnoise/IMGG-4.jpg
http://lillehem.eu/k20dnoise/IMGG-5.jpg
http://lillehem.eu/k20dnoise/IMGG-6.jpg
http://lillehem.eu/k20dnoise/IMGG-7.jpg
http://lillehem.eu/k20dnoise/IMGG-8.jpg
http://lillehem.eu/k20dnoise/IMGG-9.jpg
Wonders of modern production. Like anything you get sample variation... this is probably the real case here. Some K10's had a red one side, blue other side when dark exposures were push processed hard. The cause was never really found out. Seems the k20 has some models w/ at least the same tone l and r . You could get a better one next time.. 6400iso is really good for nothing but "need to get the shot".. certainly not quality... I doubt this is any different then any other brand w/ a possible exception of much more expensive cameras (w/ much more expensive parts)...
as much as it pains me to say this but this camera is not suitable for what you need. Maybe testing 10 others you can get a good one but...........
6400, 3200 you ALWAYS take your chances and it's best to push the initial exposure as far to the right as you can.
I don't know (or want to take the time to check) which of your samples is iso 1600. The one I looked at is 3200 and w/ a better exposure it isn't too bad though the blue l,r toning is there, but barely in the bright top and only creeping in in the shadow area. which may be normalish anyways (dumbbell picture w/ creme/beige carpet).
I don't understand why people think any of these cameras can produce gallery prints at such high iso's As the iso range goes up your dynamic range decreases significantly, and your noise increases.... it's the nature of the beast. There is good software to deal w/ some of these problems but there not in the camera so to speak.
Hint: If you need 1600 do your samples at 1600 not 3200 or 6400... then judge. Image quality starts to break down rapidly at these high iso's

Last edited by jeffkrol; 03-26-2009 at 06:18 AM.
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