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How about a 'No Compression' quality setting?

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Offline TT

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How about a 'No Compression' quality setting?
« on: 05 / March / 2010, 18:11:09 »
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CHDK adds SuperFine (thank you much) which reduces the JPEG compression to something like 2.5:1 (if I'm figuring it correctly), but is it possible to add a 'No Compression' mode?  I know that RAW is essentially that, but a 12MB file for a 2MP picture seems like overkill.  Superfine gives about 800kB files at 2MP.  Would 1:1 compression give a 2MB filesize?

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Offline reyalp

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Re: How about a 'No Compression' quality setting?
« Reply #1 on: 05 / March / 2010, 19:45:21 »
Superfine is only added on a couple of cameras where Canon left it out of the original firmware.

Raw is "no compression". Anything smaller than that would be compressed one way or another (although on the current 12 bit raw cameras you could reduce it to 10 without losing much). Not sure where you are getting "2 MP" from CHDK doesn't support any 2MP cameras.

Realistically, even at superfine sensor and optical effects are probably a bigger factor than compression. My guess is that Canon left out the superfine setting because it didn't give any significant gain in visual quality for most situations.
Don't forget what the H stands for.

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Offline TT

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Re: How about a 'No Compression' quality setting?
« Reply #2 on: 06 / March / 2010, 13:31:21 »
@reyalp

The Super-fine mode provides a noticable improvement.  It reduces the JPEG artifacts on the SX200 almost to the level of the noise at low ISOs.  There's still a little smearing that I was hoping a 'super-super-fine' or 'no compression' mode would eliminate.  Then shooting at, say, 1600x1200 (2MP) would provide a 2MB filesize while allowing zooming to 30x without resorting to 'digital' zoom, thus preserving IQ as much as possible.  Given the zoom lens, I prefer to do my framing/composing/cropping/enlarging in-camera, and not do any post-processing or RAW-JPEG conversion later on.  I'm thinking that a no-compression mode would still allow the camera to do the white balance, custom color adjustments, etc., but just wouldn't 'compress' the file.  I guess it would be equivalent to the camera doing the RAW processing, with the camera setting the WB and color adjustments, and with a resulting JPEG filesize of whatever the MP setting is.

Of course, this assumes that CHDK would have any way of controlling the actual compression level...

Re: How about a 'No Compression' quality setting?
« Reply #3 on: 07 / March / 2010, 09:03:55 »
TT! Could you show an example of the the JPEG artifacts on the SX200? In what circumstanses is it best noticable? I did not see any differences between fine and superfine.
(A 410), SX 200, (SX 280), SX 700


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Offline TT

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Re: How about a 'No Compression' quality setting?
« Reply #4 on: 07 / March / 2010, 15:31:37 »
@mastodon

Fine/Normal differences are most noticable.  Fine/Super-fine is not as obvious, but artifacts seem most notable on 'edges', such as around the text on these too samples.  There is some 'blending' of pixels taking place, sometimes involving 'noise pixels' themselves, visible in the predominately gray areas.

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Offline TT

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Re: How about a 'No Compression' quality setting?
« Reply #5 on: 07 / March / 2010, 15:33:18 »
Fine, Super-fine differences

Re: How about a 'No Compression' quality setting?
« Reply #6 on: 07 / March / 2010, 16:49:22 »
Interesting post, thanks. :)
(A 410), SX 200, (SX 280), SX 700

Re: How about a 'No Compression' quality setting?
« Reply #7 on: 15 / April / 2010, 03:29:34 »
On the A710, RAW images are substantially better than Superfine images.
1) The detail is better.
2) Canon's over-smoothing has not been applied.
3) The noise or clumpiness from the crude in-camera sharpening processing is absent.

But the compressed images have some benefits too.
1) The colors are better, and require less fiddling than starting with RAW.
2) They're compatible with many more photo editing programs than RAW files are.

It would be great to have, in addition to the original RAW file, either
A) a minimally processed TIF file, different from the RAW file only in that the colors are corrected by whatever means Canon uses to render them to truer colors.
-or-
B) An uncompressed JPEG file (or as uncompressed as possible - 99 on the scale) with color correction but no sharpening or smoothing at all. Those processes have nothing to do with JPEG compression. A really high quality JPEG could be produced much better without using them. 


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Offline fe50

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Re: How about a 'No Compression' quality setting?
« Reply #8 on: 16 / April / 2010, 01:18:53 »
1) The colors are better, and require less fiddling than starting with RAW.
2) They're compatible with many more photo editing programs than RAW files are.
Use the DNG format !  --> http://en.wikipedia.org/wiki/Digital_Negative_%28file_format%29

Quote
A) a minimally processed TIF file, different from the RAW file only in that the colors are corrected by whatever means Canon uses to render them to truer colors.
-or-
B) An uncompressed JPEG file (or as uncompressed as possible - 99 on the scale) with color correction but no sharpening or smoothing at all. Those processes have nothing to do with JPEG compression. A really high quality JPEG could be produced much better without using them.
The DNG format covers this...
The JPEG file generation is done by the Canon firmware, most probably with specialized hardware (a DSP), CHDK can't create the JPEG's itself...

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Offline reyalp

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Re: How about a 'No Compression' quality setting?
« Reply #9 on: 16 / April / 2010, 03:14:00 »
The JPEG file generation is done by the Canon firmware, most probably with specialized hardware (a DSP), CHDK can't create the JPEG's itself...
It might still be possible to tweak the parameters.

The sharpening and noise reduction (not dark frame sub) are also likely adjustable. In fact, they are adjustable in the canon firmware on some recent cameras.
Don't forget what the H stands for.

 

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