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P: Regarding JXL Compression in derived Merge/Enhance DNG Images

Forum|Forum|2 years ago
October 11, 2023
3 replies
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Why with LR CC v.13, the files panorama files are now saved as lossy files?

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Correct answer JohanElzenga

But , in previous versions of LR CC, panorama files were saved as lossless files. Is posible change this set before making a panorama?

By @tigre58

Do not look at the words 'lossy' and 'lossless', look at your image and see if there is any visible effect of this new compression method. Recreate an older panorama and compare the old massive DNG with the new, much smaller DNG. Do you have any reason to be concerned?

R

Ross2511000501vd

Participant

Hello all, I wondered if you can help me.

When taking bracketed shots, I have been merging them in Lightroom as an HDR merge. To give you an examples my RAW files are each 85MB in size. I am generally merging 5 shots. Once it has created the HDR merge, which provides a DNG file, the size is reduced to 14MB for the stacked file. Is this correct or is there something I am missing? I believed that the idea with stacking or bracketing was to retain more data from each shot. Am I wrong in thinking that the size of the output DNG file should be as large as all RAW files put together? Please do let me know any thoughts or if there is something I am missing or have done incorrectly. I have attached a sample photo showing the smaller merged file and the original RAW file.
Many thanks

Ross

reproo2773183

Inspiring

Stacking is just how the files are displayed/hidden in Lightroom.

The HDR DNG is a demosaiced Merged file it won't contain 5xRAW data, only one Layer of pixels and that single layer is now compressed, whereas the RAWs may have been lossless.

I think you are assuming a structure similar to 5 Layers in Photoshop 5, thats not whats in you DNG.

You get to keep the extra dynamic range information from bracketing because you effectively have more bits (smaller steps) to play with.

M

madbrain76

Known Participant

I'm not the one you were responding to, but I thought I would respond still.

I'm not personally assuming that any of the original raw data is preserved in the merged file - HDR or Panorama.

What I'm assuming is that the process goes like this.

1. Merge x DNG files into one demosaiced set of pixels, in RAM

2. Compress that data on disk

If LRc were properly designed, you could choose the compression method in step 2, one with lossless JPEG XL, and one with lossless JPEG.

You could then export each output DNG to a TIFF, then use a tool to compare the pixels data, to see exactly how much information was lost.

Unfortunately, the option to choose the compression for photo merge is missing in LRc, and there is thus no way to do that.

I would try to test this by comparing a previously created lossless DNG Panorama, to a newly recreated one as a loss DNG. Unfortunately, the merge algorithms have changed. I was unable to recreate one of my existing panorama in the current version of LRc. The merge algorithms change with each version of Lightroom.

It is thus not possible to keep the compression algorithm as the only variable.

A someone who can hear the difference between lossless audio and compressed audio, I think this is a choice that needs to be left to the user. Just because I have macular degeneration and can't personally tell the difference between the lossy and lossless images doesn't mean someone else won't be able to tell.

This is just a braindead decision by Adobe. They need to provide a lossless option. Also, since JPEG-XL doesn't yet have wide acceptance in other software (not even Windows Explorer shows previews), the option to switch between JPEG-lossless and JPEG XL-lossless should be there. Just like it is for regular Export rather than Merge.

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Olaf314551382lie

Participant

Ich habe Lightroom Classic Version 13.0.1 und Camera Raw 16.0 auf meinem neuen Rechner installiert.

Seitdem bekomme ich VERLUSTREICH komprimierte Panoramen und HDRs mit deutlich reduzierter Auflösung und Dateigröße (Dateityp "Digitales Negativ/Verlustreich komprimiert". Ich möchte jedoch verlustfreie DNG-Dateien erzeugen.

Mache ich etwas falsch oder haben andere das gleiche Problem? Anwendungsfehler oder Bug?

Über Tipps bin ich sehr dankbar!

Viele Grüße

Olaf

kglad

Community Expert

in the future, to find the best place to post your message, use the list here, https://community.adobe.com/

p.s. i don't think the adobe website, and forums in particular, are easy to navigate, so don't spend a lot of time searching that forum list. do your best and we'll move the post (like this one has already been moved) if it helps you get responses.

<"moved from cc desktop">

Rikk Flohr_Photography

The compression method for derived DNGs has been changed from JPEG to JPEG-XL, which provides a smaller data footprint without loss of quality.

Creating a merged DNG such as a panorama is already a “lossy” process because the merged pixel data has been demosaiced, aligned, and blended from the original photos. Using JPEG XL compression makes a much smaller visual change.

Rikk Flohr: Adobe Photography Org

C

ClintGryke

Participating Frequently

I just noticed this change today and came across this thread in search of the answer which is neatly provided thanks. However, it does raise a couple of questions. This may be pretty pedantic but it would be really interesting to know what the experts think.

So I've been experimenting with the new HDR Edit and Export feature in Lightroom. I have an Apple XDR monitor which I have been using for HDR video up to now but this ability to edit and export stills in XDR is very exciting. In fact this is how I realised the Merge to HDR DNG file had changed as I was doing a HDR merge to test the HDR editing in Lightroom Develop Module. Now in the guidance from Adobe (Edit and Export in HDR), it recommends using JPEG XL or AVIF files for export for sharing and web galleries and TIFF or PSD where additional HDR work is required. The implication here is that the lossy compression of the merged DNG file is of no noticeable importance if not doing further editing but it may well be important if doing further editing.

So my question is in the case of merged DNG files, is there any point in exporting as lossless TIFF or PSD as against JPEG XL? In other words, is the data already lost in the same way as it would be if exporting an 8-Bit JPEG originally derived from a raw file for example as a TIFF or PSD? There is a huge difference in the file sizes for sure. My main usage at the moment would be importing into Final Cut Pro and some editing may be needed there to color match my HDR video.

JohanElzenga

Community Expert

Yes, the data are lost. The fundamental difference between lossless compression and lossy compression is that in lossless compression the decompressed image is bit for bit identical to the original. In lossy compression that is not the case. The decompressed file will not be absolutely identical to the original file. Whether that leads to any practical and visible differences is another matter that I cannot answer. My own suggestion is always that the proof of the pudding is in the eating, not in reading the recipe. Try it yourself.

-- Johan W. Elzenga

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