Participating Frequently

P: Thick red/blue banding in brightened shadows of Denoised DNGs

Forum|Forum|1 year ago
June 6, 2024
33 replies
7322 views

I noticed this a few days ago but didn't realize the scale of the issue until I played around with the Exposure values and tested them to the limit.

I've attached two screenshots of the Develop module. The control image is an RAF photo with Exposure boosted to +5. The experiment is a DNG derived from the RAF, with a Denoise amount of 30. The effect manifests at all amounts from 1 to 100. However, the banding is not present in the Enhance Preview window. I have also attached the original Fujifilm RAF from my X-H2s camera (lossless compressed) and an affected DNG with Denoise.

I can't detect this phenomenon in NR conversions before LrC 13.3.

The significance should be self-evident. The banding artifacts appear in images with lifted shadows or underexposed photos with boosted brightness.

Lightroom Classic version: 13.3.1 [ 202405311538-6d7c0308 ]
License: Creative Cloud
Language setting: en-CA
Operating system: Mac OS 14
Version: 14.5.0 [23F79]
Application architecture: arm64
Logical processor count: 12
Processor speed: NA
SqLite Version: 3.36.0
Power Source: Plugged In, 80%
Built-in memory: 32,768.0 MB
Dedicated GPU memory used by Lightroom: 5,764.7MB / 21,845.3MB (26%)
Real memory available to Lightroom: 32,768.0 MB
Real memory used by Lightroom: 3,716.8 MB (11.3%)
Virtual memory used by Lightroom: 424,322.1 MB
Memory cache size: 1,238.0MB
Internal Camera Raw version: 16.3.1 [ 1889 ]
Maximum thread count used by Camera Raw: 5
Camera Raw SIMD optimization: SSE2
Camera Raw virtual memory: 2281MB / 16383MB (13%)
Camera Raw real memory: 2285MB / 32768MB (6%)

macOS

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J

Jao vdL

Community Expert

Clearly a bug indeed. Can reproduce it with the files linked above. Appears that it happens only with files from this camera which is not uncommon. I can't make it do anything like this with any of my extreme ISO images.

DdeGannes

Community Expert

@PvlKnn , understood, I was just making an observation no offense intended.

Regards, Denis: iMac 27” mid-2015, macOS 11.7.10 Big Sur; 2TB SSD, 24 GB Ram, GPU 2 GB; LrC 12.5,; Lr 6.5, PS 24.7,; ACR 15.5,; (also Laptop Win 11, ver 24H2, LrC 15.0.1, PS 27.0; ) Camera Oly OM-D E-M1.

P

PvlKnnAuthor

Participating Frequently

This bug goes beyond this particular image.

I just want to clarify: the photo was captured at ISO 640. The stated exposure compensation was applied to preserve highlight detail. There is no ISO 10,000 equivalency. The image appears as intended when you open it in Lightroom using the default settings. There was no intention on my part to process the photo with a +5 Exposure adjustment in Lightroom. I discovered the bug by accident. The RAF was denoised, and I was playing around with the resulting DNG when I noticed some odd colour artifacts, so I looked deeper into the shadows...

DdeGannes

Community Expert

The reason I asked the question of "Exposure bias" is because of the aparent significant noise in the underxposed areas of the image. Looks as if the image was captured in the equivalent of ISO 10,200 due to the 2.67 bias, just my impression. The image on the left is from the Library module compare of Denoised image vs the original raw image at 100% with edits applied.

Regards, Denis: iMac 27” mid-2015, macOS 11.7.10 Big Sur; 2TB SSD, 24 GB Ram, GPU 2 GB; LrC 12.5,; Lr 6.5, PS 24.7,; ACR 15.5,; (also Laptop Win 11, ver 24H2, LrC 15.0.1, PS 27.0; ) Camera Oly OM-D E-M1.

P

PvlKnnAuthor

Participating Frequently

The exposure bias (i.e., the exposure compensation) applied to the photo would have no additional impact on noise versus what we'd see had I used the same aperture, shutter speed, and ISO values in manual exposure mode. It's just a bias versus the camera's standard exposure index for that frame.

DdeGannes

Community Expert

I had a look at the Camera Metadata to see the Camera settings for the RAW image 1/40 sec, f5.6, ISO 680, Exposure bias -2.67.

What effect if any will the Exposure bias have on the noise in the image?

Regards, Denis: iMac 27” mid-2015, macOS 11.7.10 Big Sur; 2TB SSD, 24 GB Ram, GPU 2 GB; LrC 12.5,; Lr 6.5, PS 24.7,; ACR 15.5,; (also Laptop Win 11, ver 24H2, LrC 15.0.1, PS 27.0; ) Camera Oly OM-D E-M1.

DdeGannes

Community Expert

The screen capture is a comparison of the raw image with Denoise done on my Win 11 laptop on the current (up to date) build the GPU has limited acceleration, and the origin Denoise image supplied by the Author.

My laptop does not appear to have the experiance of the Author's Mac.

Regards, Denis: iMac 27” mid-2015, macOS 11.7.10 Big Sur; 2TB SSD, 24 GB Ram, GPU 2 GB; LrC 12.5,; Lr 6.5, PS 24.7,; ACR 15.5,; (also Laptop Win 11, ver 24H2, LrC 15.0.1, PS 27.0; ) Camera Oly OM-D E-M1.

johnrellis

Legend

I get different results than Ian on LR 13.3.1 / Mac OS 14.5 -- not a grid of squares as he got but vertical purplish and reddish banding.

But on LR 13.2 / Mac OS 14.5 and LR 13.3 / Windows 11 (no GPU in a virtual machine), I got much different results, with no strong banding, similar to Ian's result on 13.2.

I think the distinct banding / gridding and the variation of results between LR 13.3 and 13.2 indicate a clear bug.

- LR 13.3.1 / Mac OS 14.5:

- LR 13.2 / Mac OS 14.5:

- LR 13.3 / Windows 11, no GPU:

- LR 13.3 / Mac OS 13.3.1 [sic], no GPU:

DdeGannes

Community Expert

Screen capture of denoised image and raw image with edits, viewed in the Library module compare view.

Regards, Denis: iMac 27” mid-2015, macOS 11.7.10 Big Sur; 2TB SSD, 24 GB Ram, GPU 2 GB; LrC 12.5,; Lr 6.5, PS 24.7,; ACR 15.5,; (also Laptop Win 11, ver 24H2, LrC 15.0.1, PS 27.0; ) Camera Oly OM-D E-M1.