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05-13-2009, 01:13 PM   #1
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K2000 excessively noisy (-was grainy sky)

So here I was test shooting a new Tamron 70-300 Di LD when I noticed the camera seems to have a grainy rendition of the sky. It is very minor at ISO-100, but stands out at ISO-400. I don't think ISO-400 should have this much grain.

Is this a weakness of the JPEG engine? Or just Pentax's signature noise?

Don't mind the boring test subject. They are 100% crops. 100 and 400 respectively.

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PENTAX K2000  Photo 

Last edited by boom; 05-13-2009 at 08:58 PM.
05-13-2009, 02:03 PM   #2
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hm... strange! I have k2000 too, and I've never had a problem with iso400! The noise becomes visible only @ISO800 and up. The jpeg engine is not the best one, so I am using PEF only.
Try shooting in PEF and check the result in CS4
05-13-2009, 02:07 PM   #3
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I think shooting in JPEG isn't going to help you - blue skies really show up JPEG compression artifacts.

One of the best things I ever did was shoot in RAW. My images and their quality are leaps and bounds better than anything I took in JPEG mode.

Try shooting in RAW and see how that helps, additionally the higher ISO is bound to introducde some more grain. Post processing with Camera Raw will allow you to suppress some of that noise.

Go RAW .
05-13-2009, 02:25 PM   #4
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here are 2 test shots at high ISO:
Raw format, without any post-processing! only convert and resize:

shutter 1/20
iso 400
f2.8

full size 1.8Mb:
http://foto.ixbt.com/photo/440077/19604kje8C6xrLX/025B1rkdnl/323943.jpg

shutter 1/350
iso 800
f8

full size 2.2mb:
http://foto.ixbt.com/photo/440077/197549ZBc1TfHRP/s3KPrhcwxE/323582.jpg

05-13-2009, 02:39 PM   #5
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QuoteOriginally posted by grishazzz Quote
hm... strange! I have k2000 too, and I've never had a problem with iso400! The noise becomes visible only @ISO800 and up. The jpeg engine is not the best one, so I am using PEF only.
Try shooting in PEF and check the result in CS4
Actually the noise isn't that noticeable in shots other than the sky. Especially if you have other details in the photo. I've noticed the grain and noise shows up the most on gray items.

Try pointing your cam at the sky at 100 and 400 on JPEG, perhaps it's the same.
05-13-2009, 02:45 PM   #6
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Thanks for the RAW samples. I'll give RAW a try right now.. on the sky that is.
05-13-2009, 03:12 PM   #7
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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.
05-13-2009, 04:05 PM   #8
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I just tried a shot in RAW. ISO-800 developed with Picasa.

Looks like I won the lotto for noisiest sensor.

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K2000  Photo 
05-13-2009, 08:55 PM   #9
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Should I send the camera in to mother?
05-13-2009, 09:10 PM   #10
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QuoteOriginally posted by boom Quote
I just tried a shot in RAW. ISO-800 developed with Picasa.
I'm guessing these are 100% crops, whereas the other images posted were resized. That's still not great for ISO 800, but I'm also guessing that says as much about Picasa as the camera. Did you apply *any* noise reduction in Picasa?
05-13-2009, 09:19 PM   #11
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All images I posted were 100% crops. Not so for grishazzz. I don't think Picasa even has a NR feature. It just claims to support .PEF and K2000.

http://rapidshare.com/files/232730321/IMGP0740.PEF.html I've uploaded the .PEF here for anyone willing to take a peek. Perhaps it's newbie error.

I'd appreciate any help. This is my first and only Pentax camera, and could potentially leave a pretty bad taste in the mouth.

Last edited by boom; 05-13-2009 at 09:33 PM.
05-13-2009, 10:06 PM   #12
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Hello, welcome! I opened your RAW file and trying to get the brightness/shadow levels your Picassa crop show, I had dialed in +2.5 EV and still wasn't there. So, what that means to me is the image is underexposed and being pushed 3 stops is going to look horrid regardless of camera make or model. The area you show is in shadows and should be dark grey.

As for the blue sky/ airplane shots, ytterbium explained the technical reasons for noise very well, above.

Regards,
Mike
QuoteOriginally posted by boom Quote
All images I posted were 100% crops. Not so for grishazzz. I don't think Picasa even has a NR feature. It just claims to support .PEF and K2000.

RapidShare: Easy Filehosting I've uploaded the .PEF here for anyone willing to take a peek. Perhaps it's newbie error.

I'd appreciate any help. This is my first and only Pentax camera, and could potentially leave a pretty bad taste in the mouth.
05-13-2009, 10:15 PM   #13
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Thanks Mike. I'm complete raw to the whole RAW thing, I guess Picasa is doing some undisclosed processing.

You're right, I took that shot in RAW+ and I noticed that the JPEG is darker than Picasa made it out to be.

If you don't mind, could you post your development of that PEF? Or advise me what program you used?
05-13-2009, 10:53 PM   #14
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OK, here's a 100% crop of my quick edit, and here's the settings... Edited in Gimp with UFRaw plugin. First, I dialed in 1.61 + EV and set DeNoise wavelet noise reduction to 100, about a 10 on a scale of 0-100. Saved as typical highish quality jpeg.

As you can see, it's much darker than Picassa's auto levels [I assume that's what you used] and we can see red blotchy noise in the shadows, but again that's because those areas should be just about black.

RAW, I've found allows some great things. One, no jpeg compression artifacts when starting an edit! Second, because of that we can push exposure quite a ways without nasty things like banding happening. Although, again, +3 EV in shadows will make a mess. Noise reduction on a RAW file is very nice, and can for free do what the best noise reduction plugins do with jpegs and do it much better to boot. RAW, also shows less noise out of the gate than a jpeg too.

So, no I don't think it needs to go home to mother for help, you just need to practice basic photography principles with regards to exposure etc.

Regards,
Mike
QuoteOriginally posted by boom Quote
Thanks Mike. I'm complete raw to the whole RAW thing, I guess Picasa is doing some undisclosed processing.

You're right, I took that shot in RAW+ and I noticed that the JPEG is darker than Picasa made it out to be.

If you don't mind, could you post your development of that PEF? Or advise me what program you used?

Last edited by X Man; 06-04-2009 at 12:41 PM.
05-13-2009, 11:06 PM   #15
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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.

Although I do notice that grishazzz has much less chroma noise in his images.
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