A720IS + DNG4PS-2 and high ISO problem - RAW Shooting and Processing - CHDK Forum
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A720IS + DNG4PS-2 and high ISO problem

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Offline nixz

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A720IS + DNG4PS-2 and high ISO problem
« on: 17 / April / 2008, 18:35:52 »
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Hi!

I play for some time with CHDK and A720 IS. I'm using DNG4PS-2 to convert CRW into DNG, and then Adobe Lightroom or Photoshop Elements. It works pretty fine on low ISO (<= 200). With ISO set to 1600 results are STRANGE. Ofcourse high noise is normal with 8Mpix 1/2.5" CCD, but colors are awkward shifted. Its like R and G channels were shifted by constant offset?! DCRaw uses smart offset compensation from averaging pixels from dark frame around picture. Ok, here goes the pictures:

1. A720 IS camera JPEG:
http://img59.imageshack.us/img59/5581/camera1us4.jpg

2. simple DCRaw+WhitePoint setting:
http://img209.imageshack.us/img209/5923/dcrawwb1hg3.jpg

3. DNG4PS-2 (an then Adobe PSE)
http://img209.imageshack.us/img209/7130/dng4psadobe1ro4.jpg
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Offline mrproper

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Re: A720IS + DNG4PS-2 and high ISO problem
« Reply #1 on: 17 / April / 2008, 18:52:08 »
I have an issue with blue noise, but I'm too lazy to go to DCRAW. I think I tried some settings in Lightroom, obviously it's really annoying.

My camera is the A570 IS.
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Offline nixz

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Re: A720IS + DNG4PS-2 and high ISO problem
« Reply #2 on: 17 / April / 2008, 19:07:02 »
Quote from: mrproper on 17 / April / 2008, 18:52:08
I think I tried some settings in Lightroom, obviously it's really annoying.

I'm afraid it's not LR fault. It's something strange with generated DNG file. It looks about the same "blue shi^H^H^Hnoise" in other programs - eg. Picasa2.
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Offline Barney Fife

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Re: A720IS + DNG4PS-2 and high ISO problem
« Reply #3 on: 18 / April / 2008, 09:05:34 »
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« Last Edit: 22 / April / 2008, 18:11:40 by Barney Fife »
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[acseven/admin commented out: please refrain from more direct offensive language to any user. FW complaints to me] I felt it imperative to withdraw my TOTAL participation. Nobody has my permission, nor the right, to reinstate MY posts. Make-do with my quoted text in others' replies only. Bye
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Offline hiker_jon

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Re: A720IS + DNG4PS-2 and high ISO problem
« Reply #4 on: 07 / May / 2008, 21:29:14 »
Quote from: nixz on 17 / April / 2008, 18:35:52
It works pretty fine on low ISO (<= 200). With ISO set to 1600 results are STRANGE.

For 1600 ISO you need to increase the EV by 1.  Canon records the same raw data in 800 as 1600 but boosts the EV by 1 for 1600 when developing the raw.  They also do quite a bit of chroma smoothing. 
Jon
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Offline A_Str8

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Re: A720IS + DNG4PS-2 and high ISO problem
« Reply #5 on: 19 / May / 2008, 12:03:45 »
I got the same blue effect when i messed with raw, but i didn't try it enough to find that it was only at high ISO. I'm gonna tray your advice when i get home hiker. thanks.
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