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Canon A720 ISO1600 RAW, Allbest's build 50

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Offline nkmedve

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Canon A720 ISO1600 RAW, Allbest's build 50
« on: 10 / April / 2008, 08:47:53 »
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Hi!

When i shoot in RAW on my canon A720 IS I don't see any difference between ISO800 and ISO1600, in noise or exposure. (in JPEG works well) Is something wrong with release 50, or does the a720 get the ISO1600 image by simply processing ISO800 data? Someone with the same experience?

Thanks!
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Offline gueloh

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Re: Canon A720 ISO1600 RAW, Allbest's build 50
« Reply #1 on: 10 / April / 2008, 14:18:01 »
Hi nkmedve,

I have done it with build 50. The jpeg AND the raw are more noisier in iso1600.

gueloh
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Offline nkmedve

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Re: Canon A720 ISO1600 RAW, Allbest's build 50
« Reply #2 on: 10 / April / 2008, 15:16:37 »
Hi,

I've uploaded some crops, to show you what I've seen.

The first 2 are shot on ISO800 and ISO1600 (the JPEGs out of the camera), both at a shutter speed of 1/40s, aperture F/2.8. (you see that they have different exposure values because of the sensibility change). The 3rd and 4th pictures are their RAW companions (they're exactly the same). If you didn't do it yet, try it on manual exactly on the same exposure settings, like me, and tell me if you get the same RAWs.

Thanks for your time!
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Offline fudgey

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Re: Canon A720 ISO1600 RAW, Allbest's build 50
« Reply #3 on: 10 / April / 2008, 15:42:47 »
I think you may have proved that the ISO1600 mode in your camera actually sets the sensor ISO800 and applies some image processing to make the jpeg look like it was shot at ISO1600. I believe this isn't unheard of.

Does the camera shoot slower in ISO1600 than ISO800 (try measuring continous drive mode speed in pictures/second)? If it's slower, the processing may be something more sophisticated than just a difference in white balance profile applied to all high ISO jpegs...

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Offline nkmedve

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Re: Canon A720 ISO1600 RAW, Allbest's build 50
« Reply #4 on: 10 / April / 2008, 16:31:14 »
I've tested it, but no use. On ISO400-1600 I can get 20 images in 30 seconds (0.66/s), while on ISO80-200, around 40 pics in 30 seconds. (1.33/s) I've tested it on 8MP and 0.3MP JPEGs too, with the same results.
Canons might have a fast algorithm to do this kind of processing, or they intentionally slow down the iso400-800 processing, so the difference is not noticeable. I'll keep asking around in other forums too, maybe someone has heard about these anomalies.:)

Thanks for your reply!
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Offline fudgey

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Re: Canon A720 ISO1600 RAW, Allbest's build 50
« Reply #5 on: 10 / April / 2008, 17:14:50 »
Btw, did you check that ISO400 RAW is different from the 800 and 1600 ones?

This speed difference between low and high ISO photography could be software processing entirely, and who's to say it isn't an ISO400 image being brightened :)

I've been meaning to do ISO RAW comparison on my camera as well but haven't gotten around it yet. The speed decrease is very similar to yours.
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Offline nkmedve

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Re: Canon A720 ISO1600 RAW, Allbest's build 50
« Reply #6 on: 10 / April / 2008, 17:26:43 »
Yes, ISO 400 and ISO800 RAWs are different, I've tried it out on every sensibility, and only ISO1600 gives me that "something's not right" feeling:)
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Offline Barney Fife

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Re: Canon A720 ISO1600 RAW, Allbest's build 50
« Reply #7 on: 10 / April / 2008, 18:21:10 »
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« Last Edit: 22 / April / 2008, 17:18:29 by Barney Fife »
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Offline nkmedve

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Re: Canon A720 ISO1600 RAW, Allbest's build 50
« Reply #8 on: 10 / April / 2008, 18:32:50 »
The A720 has ISO1600, so narmally it should work without warming up the sensor, and in JPEG it works well, only that you probably get a JPEG which is heavily processed from an ISO800 RAW.
By the way I've tried the StereoData Maker release too, and it does the same thing, so there's probably nothing wrong with allbest's build.
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Offline Allbest

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Re: Canon A720 ISO1600 RAW, Allbest's build 50
« Reply #9 on: 11 / April / 2008, 03:37:23 »
There was discussion about ISO and ISO testing
SD1000 ISO Settings Error
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