Center-Weighted Option for Auto and Manual Tone Settings

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  • Idea
  • Updated 9 months ago
  • (Edited)

Center-Weighted Option for Auto and
Manual Tone Settings

The Auto Settings control was updated in Lightroom 7.1 to process cropped images using only the cropped pixels image data. This provides more accurate calculation of the Basic panel Tone control settings by excluding the image data not visible in the cropped image.

A problem was encountered recently by a user who was processing panorama image sets shot with a Canon 8-15mm F4L fisheye lens. To minimize the number of images required he set the lens to 12mm focal length, which reveals the lens image circle as fully black corners.

When syncing develop setting from one image to the others in the panorama set he noticed the nadir (straight-down shot) image files always looked darker than the surround image files. They are much lower in dynamic range (i.e. pavement or grass) and the image adaptive nature of the Tone controls produces different rendering. This is due to the black corners in the image, which have the same pixels values in every image file even though the scene referred lighting is different.

In trying to find a solution the ‘Idea’ presented here to provide Auto and Manual Tone Settings center-weighted adjustment was borne.

It is also useful with the current Auto Settings and Manual Tone controls to provide better rendering similar to a camera’s center-weighted exposure metering.

1) Provide an option in the Basic Tone panel to manually select a crop area used by both the Auto Settings and manual Tone controls. This crop area should be applied separately from the Crop Overlay tool so the tone rendering remains the same when syncing settings across cropped and uncropped images.

2) The Auto and Manual Tone control settings should be “image adaptively” calculated and applied using only the image data inside the crop area.

3) Provide an indicator inside the Basic panel to alert the user when a center-weighted crop area is selected.

4) (OPTIONAL, but desirable) Provide an elliptical selection tool to allow both circular and elliptical selection of the area used when calculating image adaptive Tone settings. This provides more flexibility in accurately excluding black frame areas in partial and full-circular fisheye lens images and with lenses that have high vignetting.

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Todd Shaner, Champion

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Posted 9 months ago

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Anthony Blackett

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As a clumsy workaround, you could crop the area you want to use for Auto tone, click Auto without clicking Done on the Crop tool, then either Reset the crop or change it back to where you really want to crop the image and click Done. The auto tone settings will be set according to the temporary crop area.
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Johan Elzenga, Champion

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I was thinking that too. How many people are going to use this? And the work around is simple. Make a temporary crop, auto adjust and then reset the crop...
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Todd Shaner, Champion

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Guys, thanks for the comments. Unfortunately it's a lot more complex than simply applying Auto Settings with a crop and then uncrop.
At the original post in the Lightroom Classic forum the OP demonstrates the issue with raw file samples shot using a Canon 8-15mm F4L Fisheye zoom lens. To better understand what's happening you'll need to read through that post. In addition the Auto function will not work because this is a panorama image set that will be exported and processed in PTGui. The image files must have the exact same settings applied to ensure proper stitching and blending. Further the OP (and anyone else) who wants to "manually" apply and sync Tone settings to similar image files that have fully black unexposed frame areas will get inconsistent results. This is because those areas are taken into account when applying the "image adaptive" Tone controls. The pixel data in those black frame areas do NOT change with differences in subject or scene referred lighting. ERGO: Inconsistent rendering. Anyone currently processing similar fisheye lens image in LR will NOT be able to achieve consistent and repeatable editing results.

Executive Summary

1) Here are screenshots showing a panorama file pair (Surround & Nadir) that demonstrates the issue. The Auto button has been manually applied to each individual image file to prevent the issue I outlined here and the separate 'Idea' request here. The original image file is on the left and a cropped file copy is on the right. I created separate raw file copies for the cropped images to remove using Virtual copies as the possible cause. Notice the cropped Surround file 179 is darker and the cropped Nadir 182 file is much lighter.

Here are the same screenshots, but with only -50 Highlights applied manually to each individual image file. Notice that the Nadir images are both much darker than the Surround image, which is just the opposite of the above Auto Settings images. In addition a difference was observed in the Nadir image file when viewed in the Develop (darker) and Library modules. Building 1:1 Previews corrects the difference in rendering between the modules, but it still appears as shown here. There should be no need to build 1:1 Previews to view the images at Fit view. So we have three issues including this one here.

I'm beginning to suspect the Auto function Tone settings values are being correctly calculated using only the image data inside the crop area. But then "adaptively" applied using the entire uncropped image data in the Laplacian Image Pyramid. Technical paper here.....not for the faint of heart!
So it's a sticky-wicket of what presented here is an 'Idea' and what is a 'Problem' with the current Auto Tone implementation.