Noisy RAWs in low light and unerexposed shots - RAW Shooting and Processing - CHDK Forum
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Noisy RAWs in low light and unerexposed shots

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Offline markanini

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Noisy RAWs in low light and unerexposed shots
« on: 17 / January / 2008, 23:05:17 »
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I've noticed a lot more noise in RAW files from my a570is, even att ISO 100 and 80.
I suspect that the canon firmware applies processing that removes the noise (brightness) in the JPEGs.
Anyway I'd just like to hear what you others think about this.
« Last Edit: 17 / January / 2008, 23:49:00 by markanini »
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Offline dvornik

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Re: Noisy RAWs in low light and unerexposed shots
« Reply #1 on: 18 / January / 2008, 00:51:52 »
How are you processing them? So far I couldn't get any usable results from CHDK RAW. I'm also using an A570. Converting to DNG and using Adobe converter works the best but still sucks. I'm used to Nikon DSLR RAW workflow and so far I don't see much benefit in using CHDK RAW, at least for my camera. Each picture would need extensive work to even compare to in-camera jpgs.

From what I understand the best mainstream converters (Bibble, CaptureOne, DXO) do not and will not support either CHDK RAW or non-native DNG.

I am still saving the RAW files hoping someone eventually develops a solution.
« Last Edit: 18 / January / 2008, 01:00:05 by dvornik »
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Offline hydrogen

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Re: Noisy RAWs in low light and unerexposed shots
« Reply #2 on: 18 / January / 2008, 04:48:24 »
You can control the noise reduction in the RAW settings menu.  The settings will apply to both the RAW and JPG.  If you turn Noise Reduction off, you will get noisy JPG too.

The interpolation algorithm could also introduce noise into the RAW.

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BTW...How did you get Adobe converter to convert the RAW files to DNG?  I have to use DNG4PS-2.

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Offline markanini

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Re: Noisy RAWs in low light and unerexposed shots
« Reply #3 on: 18 / January / 2008, 15:48:26 »
I use just use DNG4PS-2.

Quote from: hydrogen on 18 / January / 2008, 04:48:24
You can control the noise reduction in the RAW settings menu.  The settings will apply to both the RAW and JPG.  If you turn Noise Reduction off, you will get noisy JPG too.

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This isnt concistent with my findings on my a570is, the JPEGs always have less noise and less brightness regardless of the noise reduction setting.
Doesnt the setting rather control internal hotpixel removal? Perhaps it should be renamed to avoid confusion.

Is there any software that would let you apply the characteristics of the JPEG to the RAW image? This would also solve white balance and color balance issues.
« Last Edit: 18 / January / 2008, 15:50:56 by markanini »
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Offline dvornik

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Re: Noisy RAWs in low light and unerexposed shots
« Reply #4 on: 18 / January / 2008, 16:50:51 »
Quote from: hydrogen on 18 / January / 2008, 04:48:24
BTW...How did you get Adobe converter to convert the RAW files to DNG?  I have to use DNG4PS-2.

I meant using ACR to process DNGs created by DNG4PS-2 (and convert them either to jpgs or to 16 bit TIFFs). DNG is still not an image but it's not a RAW file either (unless it's created natively by the camera).

The problem is  good converters don't work with CHDK or non-native DNG as a matter of principle and quality control.
http://support.bibblelabs.com/webboard/viewtopic.php?p=44844&sid=f8506cf8da8435a82b53074be33256b2

DCRAW-based converters do work but they are clueless about how CHDK images actually "should" look like (how Canon converts them in-camera).
« Last Edit: 18 / January / 2008, 17:25:31 by dvornik »
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Offline dvornik

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Re: Noisy RAWs in low light and unerexposed shots
« Reply #5 on: 18 / January / 2008, 17:28:05 »
Quote from: dvornik on 18 / January / 2008, 16:50:51
DCRAW-based converters do work but they are clueless about how CHDK images actually "should" look like (how Canon converts them in-camera).

At least it's true for the a570is...
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Offline Barney Fife

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Re: Noisy RAWs in low light and unerexposed shots
« Reply #6 on: 18 / January / 2008, 18:57:41 »
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« Last Edit: 22 / April / 2008, 09:36:45 by Barney Fife »
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Offline dvornik

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Re: Noisy RAWs in low light and unerexposed shots
« Reply #7 on: 18 / January / 2008, 21:42:33 »
I don't mean to disrespect Photoline but at least on my camera (a570is) it's conversion is worse than in-camera jpg. Auto-WB helps to bring the  colors close to reality but results in some artifacts (like strong color noise in the shadows).  Overall it's not as good as the camera conversion. And the noise is completely unacceptable. It's not an objection to a RAW workflow in general - I just want RAW to work similar to how it works in SLRs.
« Last Edit: 18 / January / 2008, 23:05:32 by dvornik »
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Offline markanini

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Re: Noisy RAWs in low light and unerexposed shots
« Reply #8 on: 23 / January / 2008, 14:43:14 »
Problem solved I think:

from http://cybercom.net/~dcoffin/dcraw/:
Code: [Select]
I shot a raw photo with no light. Why does it appear all noisy, when it should be solid black?
    No matter how dark an image is, dcraw's auto-exposure stretches it so that one percent of its pixels appear white. The "-b" option adjusts this behavior, while "-4" (16-bit output) avoids it entirely.
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Offline markanini

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Re: Noisy RAWs in low light and unerexposed shots
« Reply #9 on: 23 / January / 2008, 17:48:10 »
Allright I made a series of shots changing only the ISO values, and ran the CRWs through dcraw with -W ("don't automatically brighten the image"). 
The brightness looked roughly the same between JPGs and corresponding RAW output until ISO 1600 where the RAW was identical to ISO 800 yet the JPEG was twice the brightness of ISO 800.
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