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05-13-2009, 11:36 PM   #16
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You're looking at about 2 stops underexposure in the RAW file you posted. No 10MP APS-C camera would do significantly better at ISO 400 in those conditions.

Here's what it looks like run through Adobe Camera Raw, exposure corrected (+1.95 EV) with some chroma NR:



It would be more interesting to see the RAW files of the sky, since unless you have severely underexposed the sky as well, it is true that it really should not be that grainy.


Last edited by Erik; 05-13-2009 at 11:44 PM.
05-13-2009, 11:54 PM   #17
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This is a 100% crop from a correctly exposed RAW file at ISO 400 on a K200D (same sensor as K2000):



No noise reduction whatsoever. This is what you should be looking at if exposing correctly. Now here, with the same conditions but underexposed by 2 stops and boosted 2 stops in RAW processing:



This is just how digital cameras work. Expose to the right, look at the histogram, or you're going to get excessive noise.
05-14-2009, 08:20 AM   #18
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QuoteOriginally posted by boom Quote
Thanks for that. I believe the center of the image is correctly exposed, but I wanted to illustrate the noise in the darker extremities of the image.
And in that case, I'd say it is quite normal. 100% crops of the shadow areas will look noisy. That much more so if you lighten the those shadows, and that much more still if you don't apply any NR at all while you're at it. This is totally normal. The reason the other images posted didn't look like that is that they weren't 100% crops of shadow areas that had been lightened and no NR applied. All cameras would produce results like you posted if you performed the same experiment.

Summary:

"Doctor, it hurts when I do *this*"
"So don't do that"
05-14-2009, 08:38 AM   #19
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QuoteOriginally posted by ytterbium Quote
Because Si (CMOS,CCD and similar) sensors are most sensitive to near infra-red and decrease when approaching blues/violets:

To equalize this difference you have to amplify blue channel more than others, what essentially means that the blue channel has higher ISO.

And when you're shooting blue sky you emphasize this effect . In such situation the blue channel noise is even more dominating since there are no other colour information to mask it which has much lower noise component than blue channel. And you can observe this with most sensors, although CMOS tends to improve this a bit.
That's a very good explanation.

05-14-2009, 09:07 AM   #20
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QuoteOriginally posted by Erik Quote
It would be more interesting to see the RAW files of the sky, since unless you have severely underexposed the sky as well, it is true that it really should not be that grainy.
Erik,

I have uploaded RAW files of the sky.

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Please have a go at them. They were taken at ISO-400, Av mode. I didn't try to underexpose them intentionally at least.
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05-14-2009, 09:27 AM   #21
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I'm gonna say that the one with the sky and the tree is a little underexposed as well -- the camera's meter gets a little bit tricked by the bright blue sky. I would dial in +1 exposure compensation when taking pictures like this. If you look at the histogram there's nothing in the right third of it which is not optimal from a signal/noise ratio perspective.

Anyhoo, I think that 1) the underexposure is making things look a little worse than they have to be and 2) apparently Picasa just doesn't process RAW files very well with regards to NR. I ran the sky picture through Lightroom real quick and while there is still a certain graininess to the sky, the annoying chroma noise is gone almost completely after applying even Adobe's default 25% chroma reduction.

I don't think there is anything faulty with your camera. If you feel uncomfortable, try getting your dealer to let you try another K2000 and see if it is the same.

The K2000 is neither significantly better nor worse than other cameras in its class regarding noise. (Well, it kind of obliterates the Sony A200, but...) Check the links below. Pentax does tend to take more of a "hands off" approach to noise than its competitors, though -- the philosophy is that preserving detail is more important than introducing a little grain. Some like it, some don't, but if you want to smudge out the noise at the expense of detail like Canon does by default, you can do it in your RAW converter.

Pentax K2000 Review: 32. Compared to (Higher ISO): Digital Photography Review
Pentax K2000 Review: 17. Photographic tests (Noise): Digital Photography Review
05-14-2009, 09:30 AM   #22
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note in the exif the contrast is set to hard, and sharpness to high. these will both help amplify noise.
05-14-2009, 09:49 AM   #23
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Erik,

Thanks for the information. Actually, I shot all these in RAW+ and the 100% crops (of the sky at least) are from the JPEG files.

I could go to a store, but their cameras are bound to the stand by security cables. I was hoping another K2000 user could provide an example, in particular of the sky.

Lowell,

The settings are as it is out of the box.

05-14-2009, 12:01 PM   #24
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I'm not sure if I can help you because I'm a K-M JPEG shooter. What you could try is set Shadow Compensation to OFF and set Noise Reduction to WEAK and you might end up with a little less noise in your pics.
05-14-2009, 12:45 PM   #25
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QuoteOriginally posted by Thirteen Quote
I'm not sure if I can help you because I'm a K-M JPEG shooter. What you could try is set Shadow Compensation to OFF and set Noise Reduction to WEAK and you might end up with a little less noise in your pics.

Hi,

You sure can. I shoot JPEG as well. I was only experimenting with RAW in this thread because someone said it might help, and see how badly I screwed that up In fact, the very first two pictures in this thread were straight from the camera, with essentially default settings.

Also, NR doesn't work on ISO-400. Only 800 and above.

Thanks.
05-14-2009, 03:07 PM   #26
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QuoteOriginally posted by Erik Quote
This is a 100% crop from a correctly exposed RAW file at ISO 400 on a K200D (same sensor as K2000):
No noise reduction whatsoever. This is what you should be looking at if exposing correctly.
Erik,

Even without NR, it seems there is less chroma noise in your sample. I now accept that the grain is normal as I'm seeing it in most samples as well, but perhaps my chroma is abundant.
05-14-2009, 04:38 PM   #27
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Yeah, but his was at ISO 400, not ISO 800, and it was neither blue nor was it underexposed. Again, your samples look pretty normal to me - *for images shot and processed the way you did*. None of the other examples posted looks as bad because none were shot under the same conditions as yours.
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