RAW average: interesting examples here! - page 4 - RAW Shooting and Processing - CHDK Forum

RAW average: interesting examples here!

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Re: RAW average: interesting examples here!
« Reply #30 on: 19 / March / 2008, 05:16:21 »
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None handy. Tested this long ago when it was first reported shortly after "NR Off" was first introduced over 1/2 year ago. They were all just throw-away files. Someone else first reported the discrepancy that NR OFF was less noise. I confirmed it on my own. Anyone can. It might matter on the make and model of camera too. Hard to tell.

I have now long since suspected that this was just another way of Canon trying to get people to buy their more expensive cameras where they could make even more money selling "parts" (necessary lenses). Intentionally introducing more noise on their lower-end lines to help confirm one of the often-mentioned minor drawbacks of P&S cameras. Afterall, who was to know, nobody would ever be able to turn it off to find the difference. :)

But yes, noise seemed to slightly increase when I would use ISO override for lower ISOs. Looking like the same level of noise as if I had noise reduction turned ON when using normal camera functions, not override functions. I post-process all my photos anyway, so noise is never huge a concern of mine.

Come to think of it, I never did test NR ON with Low ISO Override (I permanently keep NR off after I saw what Canon was doing to my images), maybe they work in reverse with ISO override and it would help with low ISO.



Hello,

can you make this a bit more clear to me?
Short exposures: You say NR Off gives better images? (At least PP removes Noise better)?
Long exposures: You say NR Off gives better images? But one has to remove hotpixels afterwards?

Thanks for sharing your experience!

obitus

Re: RAW average: interesting examples here!
« Reply #31 on: 19 / March / 2008, 19:12:08 »
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« Last Edit: 22 / April / 2008, 13:55:03 by Barney Fife »
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Re: RAW average: interesting examples here!
« Reply #32 on: 20 / March / 2008, 04:59:22 »
Hello Barney Fife,

OK thanks for your reply. About asking questions ... I partly agree with you, one has to try things out one one's own. But then again I am having a hard time judging or finding those things on my own. Like that images are not sharp in F/8 - it just never occurred to me, now I know at try to shoot at F/4,5.

Just tryin' to get the maximum out of my S3Is I guess, so that I don't do major issues in exposure, focussing and so on so that I can focus more on actually taking the picure (framing, composition ...). Isn't this what we all want  :)

obitus

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Offline gabriele

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Re: RAW average: interesting examples here!
« Reply #33 on: 20 / March / 2008, 12:27:31 »
wow the image is fantastic. there is almost no purple fringing at the corners
it is excellent. i would very much like to use this feature. however i have to capture the images with remote capture using a computer. anyone know if the raw images are available if the image is captured with a computer and an SDK ?


Fringing is all due to camera lenses, better lenses give better pictures with less aberration.
If you don't see any colour fringing is because of the function implemented in many RAW pictures processing software such as Adobe Camera RAW (like in the pictures) or RAW Therapee that lets you remove the fringing via software. (as I did in the pictures). If you don't take pictures in RAW mode, the camera does it automatically.

Like that images are not sharp in F/8 - it just never occurred to me, now I know at try to shoot at F/4,5.

obitus

This is due to less light reaching the sensor, the smaller is the aperture, the less is the resolving power as it happens with telescopes. Bigger is the telescope, more details you can see.
« Last Edit: 20 / March / 2008, 12:30:38 by gabriele »


Re: RAW average: interesting examples here!
« Reply #34 on: 20 / March / 2008, 15:06:50 »
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« Last Edit: 22 / April / 2008, 13:55:29 by Barney Fife »
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Offline PhyrePhoX

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Re: RAW average: interesting examples here!
« Reply #35 on: 20 / March / 2008, 15:53:19 »
speaking of purple fringing and noise reduction: on my a620 when i disable noise reduction in raw menu, i get a result not only as ugly as george bush, but also discarding as much information as george bush.
i speficially made this test for this thread, and while i always knew about the "purple stuff" (are these the dreaded hotpixels?) i never noticed that i actually have MORE information in the picture using noise red ON. just compare the two images, in the one with the purple clouds are much less information stored. you can already see that in filesize (with NR: 1,5 MB & without: 0,7 MB). this scares me.

you can find high-res pics of these examples here: zSHARE - img.zip

i dont get it.

ps. you can find the noise in left edge and in the top edge. its always the same.

settings: 65 seconds, iso 50, f: 2.8
« Last Edit: 20 / March / 2008, 15:55:06 by PhyrePhoX »

Re: RAW average: interesting examples here!
« Reply #36 on: 20 / March / 2008, 16:00:44 »
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Offline PhyrePhoX

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Re: RAW average: interesting examples here!
« Reply #37 on: 20 / March / 2008, 16:08:31 »
okay, so NR reduces the ampglow, by use of the darkframe substraction. but how come the NR picture is twice as big as the NR off picture? in the NR off picture i not only see more noise (well, duh!) but i cannot even see the chair anymore (which can clearly be seen on the NR pic).
(by the way i always thought chdk writes the real shutter speed somewhere into the exif?)


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Offline gabriele

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Re: RAW average: interesting examples here!
« Reply #38 on: 20 / March / 2008, 16:11:30 »
OT (non-CHDK related):
This is partly correct, in that diameter will define when you cannot get any more resolving power due to diffraction effects, but the problem with image resolution degrading at widest apertures is due to lens quality and has nothing to do with diffraction. Larger lenses are harder to configure for diffraction-limited resolution. This is why all DSLR lenses cannot be used as freely wide-open.

I know this but Obitus was talking about shoting at f/8 and I won't consider that wide aperture! ;-)
I'm also aware of what is chromatic aberration because I am an astroamateur, that kind of aberration is pretty common in refractor telescopes (not the very expensive ones) so I know about blooming.
What I didn't know is that you call it purple fringing, I thought he was still referring to CA because purple fringing usually occurs only in very bright pictures or when a strong light source comes from one side as in landscapes pictures where the Sun is shown. Blooming usually saturates all the pixels over and under the light source. This is why many astronomy CCD nowadays are equipped with anti-blooming mechanisms. I don't think a picture like the one I took could present purple fringing but it had some CA that has been removed with Adobe Camera RAW.
« Last Edit: 20 / March / 2008, 16:23:00 by gabriele »

Re: RAW average: interesting examples here!
« Reply #39 on: 20 / March / 2008, 16:23:15 »
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« Last Edit: 22 / April / 2008, 13:56:09 by Barney Fife »
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