[lm4187]

The banding has little to do with JPEG compression and a lot to do with the 8-bit/channel color limitations of the JPEG format. Normally it is not much of a problem, but with large regions of primary color and a shallow gradient (such as the sky), 256 shades just ain't enough. Gradients appear as discontinuities. As noted above, PP can make the problem worse.

Steve is correct. When you go to JPG, you are going from 12- or 14-bit color in RAW (not sure of your camera) to 8-bit in JPG. Even setting the lowest compression (best spatial resolution) will not alter this fact; JPG is lossy, even if it is only in dynamic range.

Just for fun and to show an extreme case of what you are seeing, try this:
1. Take one of the better images and open to edit in PSPX6.
2. Go to Image->Decrease Color Depth->[Any Lower color depth]
3. In the dialog box, select Nearest Color for the Reduction Method.

The result will show the effect of reducing the dynamic range of the final image--showing banding (also called False Contouring).

[As an aside, our eyes are great at detecting edges, but not so great at perceiving gradients of color.]

If you select Error Diffusion for the Reduction Method, the algorithm will try to smooth the boundaries between levels, albeit not perfectly--still leaving a bit of banding.

Also, the order in which processing is applied can affect the final result. Maybe reducing RAW to 8-bit RGB with Error Diffusion first might give better final results.

Final thought. I have two monitors with differing color quality (even though calibrated with SpyderPro). The lower quality monitor shows a much more pronounced effect of the banding, so your monitor might be exaggerating the banding a little.

JPG, web standards, and monitors all conspire to give us the least common denominator of image presentation.

My two cents. Hope this helps.

Cheers,
Lou

[Imageman]

Ok, I accept what your saying.


You working on 48mb TIFFS for all your post processing right through to printing.


Yes I have used Jpeg2000, plus a dozen other softwares for image manipulation.


Jpeg2000 is better than Jpeg, but I don't use Jpegs for any purpose other than to distribute images in a convenient manner for viewing and emailing, and pretty much to be avoided for any other purpose. I would never store an image as a Jpeg and I would never print from a Jpeg unless I had to.


I work exclusively in TIFF, I avoid Jpeg and PNG for the following reasons


This is current thought on Jpeg:-
The JPG format is not suited to images with text, large blocks of solid color, and simple shapes with crisp edges


You have large blocks of solid colour


This is current thought on PNG
PNG images, like GIFs, are not well suited to photographs. It is possible to get around the banding issue that affects photographs saved as GIF files using true colors, but this can result in very large images


You suffer banding


I am reluctant to install yet more software simply to try to resolve this issue for you when I don't expect there can be a resolution.


Theres nothing else I can say Jpeg creates bands, PNG creates bands, You can use Jpegs and PNGs but you have to be careful. PNG and Jpeg are unsuited in my opinion to high quality photographs, I wont change my opinion, your experience simply confirms that Jpegs and PNGs are unsuitable for high quality photography.


I have said that I upscale to minimise degredation and to produce smoother looking files in post processing, but you suggest this is somehow wrong, yet I don't suffer banding and you do.


I do suffer banding in Jpegs on high compression, but 50% compression and below are visibly band free. Bands always exist however, all Jpegs have to create bands, its the way they work.


All I can say is I hope you get a resolution.

[RayeR]

>lm4187
Yes, dithering came in my mind soon but I don't know any program that allows me to dither when reducing from 48bpp to 24bpp. PSP offers this option if you reduce colors from 24bpp to 16bpp or less. I know this well. But if you reduce from 48bpp to 24bpp there's no such dialog. Also in Photoshop CS4 if I switch to 24bpp its done simply without any dialog about dithering. I made some experiments with it but dithering is not performed and I got same result saving blurred 48bpp gradient to jpg as if I reduce it first and then save. BTW the residual or induced gaussian noise works similar as dithering I learned...

>Imageman
OK, you simply have higher requirements and are so sensitive that you see banding in 24bpp images but for many others it's good enough. I didn't complain on uncompressed 24bpp images they seems to me smooth enough. Thats the difference. Again the thread was about tuning compression of 24bpp images and not about if is better to use 48bpp. Of course 48bpp is always better (if proper input) but for what price. Do you listen mp3? Or pure SACD/DVDA/Flac? Same choice...
I don't understand your thoughs about PNG. Yes of course because it's lossless it will be larger than JPEG. But you can choose 48bpp too and you get smaller files than TIFFs, PNG compression is slightly better. Yes I told that upscaling images cannot add any usefull information to taken image (that is little bit blurred by it's nature) but if you'd like to waste your disk space you have the same right to do as I like to save my space.

[Imageman]

OK STOP RIGHT THERE


Your the one with the problem. You see banding


I don't have a problem. I don't see any banding or any other issue.


Your workflow fails, My workflow works. Is that clear.


Good


Stop preaching. Start listening

[lm4187]

Alas. We're trying to reproduce an analog world with digital sensors. Limitations emerge.

Additonal, and final, thought: What happens if you save the image as RAW+ and let your camera do the processing?

BTW. Thanks for reminding me to break out my polarizing filter to enhance the sky!

Cheers.
Lou

[RayeR]

Additonal, and final, thought: What happens if you save the image as RAW+ and let your camera do the processing?

I use RAW+ to have also jpegs that are better for quicker viewing (and delete imediatelly bad photos) and I didn't noticed banding there. Pentax don't denoise so hard and the natural mild noise present in the sky prevent jpeg compressor to replace a block by single color.