A720IS + DNG4PS-2 and high ISO problem

nixz

2

« 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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mrproper

92

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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nixz

2

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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Barney Fife

1157

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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hiker_jon

284

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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A_Str8

59

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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