Artifacts with super resolution on lossy compressed DNG with cr16

[EduP]

Hi there,

I'm currently testing the new lossy compression feature in Camera Raw 16, and I'm finding the file size reduction to be quite impressive! However, I've noticed some unusual artifacts when using super resolution on a lossy compressed file, which I'm not observing with a CR15 lossy compressed file. I'd like to know if this is a tradeoff of the file size reduction or if it's a bug.

Thanks,

Edu

[MadManChan2000]

Can you explain the workflow (steps) you followed to produce the image on the right?

Is your original file a raw file or something else?

[EduP]

I adjusted the original NEF using Camera Raw 16, and then converted it to lossless and lossy DNG formats in Camera Raw 16. I processed the lossy DNG (CR15) with DNG Converter 15.2, and finally, I applied super resolution to all three files in Camera Raw 16. I'm sending you the files in a private message.

Thanks!

[MadManChan2000]

Thanks for explaining that.  In general I would always recommend using Super Resolution on the original (in this case, NEF) data.  This is for two reasons.  First, Super Resolution works best on raw (mosaic) data, such as the Bayer mosaic data in a NEF (Super Res applies both demosaicing and upsampling at the same time, for a better result).  Second, Super Resolution will generally amplify any lossy compression artifacts (esp. in RGB data).

Note that in ACR 16, if you apply Super Res on your NEF, the result DNG will be quite a bit smaller than when you previously used ACR 15.x, because the result will be compressed using the new method (JPEG XL).

In other words, this flow should produce the best output (with good file size):

NEF -> Super Resolution (demosaic + upsampling) -> result is compressed DNG

Whereas the following flow will also produce small files but will compromise the quality and hence not recommended:

NEF -> Lossy Compressed DNG (demosaiced linear RGB image) -> Super Resolution (upsampling only) -> result is compressed DNG

[pepherrero]

Dear Eric,

Thank you for the explanation. I understand that the workflow I described is not ideal, and I don't intend to do it that way. In fact, I was merely testing the robustness of the new lossy compressed DNG format. I use lossy compressed DNG to archive my event photography raw pictures as a more robust alternative to JPEG, as I have no contractual obligations and no interest in keeping the files long-term. However, occasionally, I am asked to recover or post-process a file.

In this context, can I conclude that the new compression scheme is less robust and more prone to artifacts than the old one? Is it possible that if you need to post-process a lossy compressed file, you would be in a better position with a 15.x lossy compressed file?

Thanks,

Edu

[EduP]

Apologies for the user change; I was using another computer. After conducting more tests with the compression scheme, it seems clear to me that it's dialed up to eleven. All the noise texture is lost, and there are artifacts everywhere. In my opinion, the old compression was much more balanced. Would it be possible to have control over the DNG compression scheme and revert to the old one? 

Thanks, 

Edu

p.s. I can send the original files if anyone is interested.

[MadManChan2000 · Accepted solution]

Understood.  We're going to have some more options in the next release of Camera Raw that will enable you to achieve better quality, with lossy.

The current lossy compression DNG settings available in ACR 16.0 were intended with Smart Preview (proxy) workflows in mind; that is, as a temporary stand-in for the original..

Stay tuned for some improvements in this area.

[EduP]

Thank you, Eric! Very happy to know that the compression scheme will improve, and we will have the option to enhance the quality.

Best regards, 

Edu

[deejjjaaaa]

Eric - can somebody in Adobe please update https://helpx.adobe.com/content/dam/help/en/photoshop/pdf/dng_commandline.pdf

one can assume that the file needs to include options like -dng1.7 ... one can make a guess, but it still better to have an updated version of the command line manual, no ?

[MadManChan2000]

The following is a draft of the updated DNG Converter command line documentation that we'll post on the official site before too long.  Not all the options are available yet (esp. -lossyMosaicJXL and -losslessJXL), but the other JPEG XL related compression settings do work.  There are many examples that I've added to the docs for typical use cases.  For example, for high quality lossy, try:  -dng1.7 -lossy -jxl_effort 7 -jxl_distance 0.1 [input file]

As an example for a source non-DNG Bayer file that is lossless compressed using the native format.

Original: 45 MB

Convert to DNG (lossless JPEG, prior to 1.7): 38 MB

Convert to DNG (lossy JPEG XL, effort 7, distance 0.1): 16.4 MB

Convert to DNG (lossy JPEG XL, effort 7, distance 0.2): 9.9 MB

Convert to DNG (lossy JPEG XL, effort 7, distance 0.3): 7.2 MB

[deejjjaaaa]

Thank you !!!

[deejjjaaaa]

there is a small typo in PDF  in examples part :

"Convert a mosaic raw file to a linear RGB DNG (demosaiced) with lossless JPEG compression:
EXE -linear DSC0001.NEF"

shall be "-l", not "-linear" 

[MadManChan2000]

Thanks for reporting that!  We've now posted the document (with the fix) on the main DNG page.

[deejjjaaaa]

Thank you !

PS: any chance original raw -> DNG conversion in Adobe products (DNG converter, etc) have a more consistent approach to "maker notes" transfer ( to DNG output ) ? those tags are not being copied from Canon CR3 raw files and that leads to certain issues ( which can be fixed by using exiftool afterwards to copy them , but that's an extra step)