Lightroom: Low Quality Downscaled Views in the Develop Module – Part II

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  • Problem
  • Updated 6 years ago
  • Not a Problem
This is a continuation of TK’s bug report with the same name at this link:

http://feedback.photoshop.com/photosh...

The issue at this post concerns application of noise reduction to the LR loupe and Develop module preview images at less than 1:1 size (i.e. downsampled image). The Adobe LR team has fixed this issue in LR4, which now applies noise reduction properly to all preview sizes. For that we are very thankful, but other equally important issues with LR’s preview view “accuracy” still have not been addressed.

There have been numerous reports of LR ‘Export’ or ‘Edit In External Editor’ images not matching the original raw image when viewed in LR. In virtually all of these cases the exported image shows a color shift or overall lighter tone than the original raw file. In most all cases the images were either shot at very high ISO (i.e. high noise), had very high Sharpening applied, or both. LR3 and LR4 exhibit this “bug” and it appears no one has identified the actual cause. Here are two examples in the LR Forums:

http://forums.adobe.com/message/3931108

http://forums.adobe.com/message/4333196

In the 2nd post above, contributor Dorin Nicolaescu-Musteață suspected the cause was LR’s resampling algorithm used for downsizing LR’s Loupe & Develop preview images and Export images. The following test was performed to test this theory:

I created three files using LR's default develop settings and the following Export settings

1) Full-size with no output sharpening
2) 900 x 600 size and Screen Standard sharpening
3) 900 x 600 size and no output sharpening
(All three use TIFF, ProPhoto RGB, and 16bit output)

The downsized (i.e. resampled) exported images 2 & 3 look identical and lighter in both PS CS5 and LR when compared to the original raw image file. The full-size exported image file looks the same as the original raw image file in PS and lighter in LR. Setting LR’s Sharpening Amount to 0, or Luminance Noise Reduction to a high level (>50) greatly reduces or eliminates the lightening observed.

I also used PS CS5/ACR6.6 to open the raw image file and create the above three files. All three of the PS/ACR processed images look identical in color and tonality with no issues. This confirms there is an problem with LR's screen preview and develop export resample algorithms, which is visible with very high ISO noisy image files, and/or highly sharpened image files.

Complicating trouble-shooting and identification of this resample algorithm issue is LR’s Histogram, which does not apply sharpening or noise reduction to its display. This also explains why many people are seeing large differences in LR’s histogram when comparing exported files to the original high ISO raw files.

Since tonality changes are being applied to both LR’s downsized onscreen previews AND actual exported files, I consider this a serious “bug.” I sincerely request the Adobe LR team consider investigating and correcting this issue with the downsampling algorithms.

Thank You,

Todd Shaner
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Todd Shaner

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Posted 7 years ago

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Paul Tansley

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Have just come across the same issue - in the last few days. Probably because they are all high ISO images. Posted about it here.

http://feedback.photoshop.com/photosh...
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Todd Shaner

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Try downsizing the image file to say 900 x 600 using the LR Export module, and also from a full-size export copy inside PS. Compare both downsized 900 x 600 images inside PS. If the LR image looks lighter and/or has less conrast then it is the downsampling algorithm problem I have outlined in this report.
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Todd Shaner

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The current workaround for this issue is to do all critical image review at 1:1 view in the Develop module, especially for high ISO images with noise.
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Dorin Nicolaescu-Musteață, Champion

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Official response: This is by design. Exporting and rendering of reduced resolution copies is done from a lower res pyramid level.
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Todd Shaner

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Thanks Dorin. I had a discussion with Andrew Rodney concerning this issue:

http://forums.adobe.com/message/49757...

Using 1:1 view is the best workaround as explained in the above post, since it accurately displays the image as it will appear after export. In most cases this is encountered due to applying excessive sharpening and/or insufficient Luminance NR to high ISO images. Using 1:1 view to adjust sharpening in Luminance NR is always the best practice and will help minimize the issue, especially with high ISO images.

It is a current trade-off of down-scaled display accuracy versus LR performance, which has an easy workaround. It is not a problem that needs to be addressed further at this time, but I suggest adding something to the online LR Help. There have been a number of recent posts in the LR forum concerning LR "view differences." We could then point them to an explanation and procedure in the "official" online LR Help or FAQs. It's difficult enough for me to understand and I've been using PS since 1996 and LR since version 1.0.
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Paul Tansley

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OMG - I now understand why the views look so different, but that has opened up a whole new question. Why would you do this Adobe?

I've been reading through the other thread you linked Todd. Useful stuff. I had no idea that the Preview I view in Preview mode would be anything but accurate. Turns out that even in Dev mode the preview isn't accurate. That's terrible surely? I rely on what my eyes see so adjust my images accordingly. I cannot possibly work through a whole wedding shoot at 1:1 in Dev mode. Would be madness.

So, it would appear from what Andrew Rodney points out that in reality it's a speed trade off. If the previews were accurate, then it would take longer to show the preview. There's something Adobe should be working on as a major new feature.

I've always relied on PS showing me the truth. I naively thought LR did the same. It would appear not.

Great shame, but at least I now have some further understanding as to why - and I have a way of seeing the image accurately (albeit if I have to choose 1:1 in Dev mode).
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Todd Shaner

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Yes, it is a speed trade-off. One possibility is for Adobe is to add GPU acceleration support for the display image rendering, similar to what is available in Photoshop CS6. Unfortunately PS and LR operate dramatically different (i.e. LR is non-destructive) – It may not be that easy to add GPU acceleration to LR. I'm sure Adobe is working it or a similar solution.

It's primarily an issue with very high ISO images when using insufficient Luminance NR and/or over-sharpening. If that's the look you want then your only option for previewing in the Develop module is to use 1:1 view. For more normal images with sufficient Luminance NR and moderate sharpening applied the down-scaled view tonality is very close.