• site home
  • blog home
  • galleries
  • contact
  • underwater
  • the bleeding edge

the last word

Photography meets digital computer technology. Photography wins -- most of the time.

You are here: Home / The Last Word / Lightroom and Photoshop Exposure controls, Part 5

Lightroom and Photoshop Exposure controls, Part 5

April 18, 2013 JimK 2 Comments

[Added after the original post. Eric Chan has informed me that there are two image-processing pipelines in Lightroom: output-referred, and scene-referred. Raw files get the scene-referred pipeline. Integer TIFFs get the output-referred pipeline. Therefore, the TIFF test images are getting a different set of processing than LR applies to raw files.]

I can’t just leave you with a whole bunch of unexplained graphs, can I? In order to make sense out of all the data on color errors when Photoshop Exposure adjustment layers and Lightroom Exposure control tweaks are used to correct underexposed images, I’ve computed the CIEL*a*b* Delta E’s for each of the 121 color patches in the test image and averaged them, giving an average Delta E for each program for pushes between zero and four stops.

Here’s the graph:

I’ve plotted the results for both Process Version 2012 (the current Lightroom algorithm) and Process Version 2010 (the Lightroom 3 algorithm). There isn’t much to choose between them.

To get the curves, I corrected all the values in the sample images by dividing them by the ratio of the mean of the luminance values in the sample image and the mean of the luminance values in the test (exposed for a 0 EV push) image. That corrects for Exposure slider settings that aren’t quite right.

The Lightroom color errors aren’t huge, but they are significant. They make me think twice about blithely underexposing and pushing hard in Lightroom. The Photoshop Exposure adjustment layer seems to work virtually perfectly.

I would expect Adobe Camera Raw to perform like Lightroom.

The Last Word

← Lightroom and Photoshop Exposure controls, part 4 Lightroom and Photoshop Exposure controls, Part 6 →

Comments

  1. Rex Naden says

    April 23, 2013 at 1:24 pm

    I sent this to Eric for possible comment Saturday- Rex

    Reply
    • Jim says

      April 23, 2013 at 2:28 pm

      Rex, Eric and I are in daily communication about this on LuLa. It turns out that there are two image-processing pipelines in Lightroom: output-referenced, and scene-referenced. Raw files get the scene-referenced pipeline. Integer TIFFs get the output-referenced pipeline. Therefore, all my test images were getting a different set of processing than raw files do.

      I’ve done some testing with real raw files, and determined that Lightroom Exposure adjustments have mean errors of around 1 Delta-E when photographing the same test pattern off the monitor, and worst-case errors of about 4 Delta-E. However, there’s a lot of noise in the real camera testing, and the real situation is probably a lot better than that.

      I’m trying to do some testing with floating-point synthetic TIFFs, which Eric says gets the scene-referenced pipeline. It’s taken me a while to learn enough about TIFF tags to have Matlab write files that Photoshop and Lightroom like, but I’m there as of this morning.

      Everything looks great in Photoshop. However, when the files are brought into Lightroom, they are much more chromatic and brighter than they are in Photoshop. When exposted from LR as 16-bit integer TIFFs, they are still too bright and too chromatic. In addition, when analyzed in Matlab, the exported images have greatly distorted CIELab scatter plots, possibly because of gamut mapping, and possible because of something else.

      I think I have to track down the source of the brightening.

      Jim

      Reply

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

May 2025
S M T W T F S
 123
45678910
11121314151617
18192021222324
25262728293031
« Apr    

Articles

  • About
    • Patents and papers about color
    • Who am I?
  • How to…
    • Backing up photographic images
    • How to change email providers
    • How to shoot slanted edge images for me
  • Lens screening testing
    • Equipment and Software
    • Examples
      • Bad and OK 200-600 at 600
      • Excellent 180-400 zoom
      • Fair 14-30mm zoom
      • Good 100-200 mm MF zoom
      • Good 100-400 zoom
      • Good 100mm lens on P1 P45+
      • Good 120mm MF lens
      • Good 18mm FF lens
      • Good 24-105 mm FF lens
      • Good 24-70 FF zoom
      • Good 35 mm FF lens
      • Good 35-70 MF lens
      • Good 60 mm lens on IQ3-100
      • Good 63 mm MF lens
      • Good 65 mm FF lens
      • Good 85 mm FF lens
      • Good and bad 25mm FF lenses
      • Good zoom at 24 mm
      • Marginal 18mm lens
      • Marginal 35mm FF lens
      • Mildly problematic 55 mm FF lens
      • OK 16-35mm zoom
      • OK 60mm lens on P1 P45+
      • OK Sony 600mm f/4
      • Pretty good 16-35 FF zoom
      • Pretty good 90mm FF lens
      • Problematic 400 mm FF lens
      • Tilted 20 mm f/1.8 FF lens
      • Tilted 30 mm MF lens
      • Tilted 50 mm FF lens
      • Two 15mm FF lenses
    • Found a problem – now what?
    • Goals for this test
    • Minimum target distances
      • MFT
      • APS-C
      • Full frame
      • Small medium format
    • Printable Siemens Star targets
    • Target size on sensor
      • MFT
      • APS-C
      • Full frame
      • Small medium format
    • Test instructions — postproduction
    • Test instructions — reading the images
    • Test instructions – capture
    • Theory of the test
    • What’s wrong with conventional lens screening?
  • Previsualization heresy
  • Privacy Policy
  • Recommended photographic web sites
  • Using in-camera histograms for ETTR
    • Acknowledgments
    • Why ETTR?
    • Normal in-camera histograms
    • Image processing for in-camera histograms
    • Making the in-camera histogram closely represent the raw histogram
    • Shortcuts to UniWB
    • Preparing for monitor-based UniWB
    • A one-step UniWB procedure
    • The math behind the one-step method
    • Iteration using Newton’s Method

Category List

Recent Comments

  • bob lozano on The 16-Bit Fallacy: Why More Isn’t Always Better in Medium Format Cameras
  • JimK on Goldilocks and the three flashes
  • DC Wedding Photographer on Goldilocks and the three flashes
  • Wedding Photographer in DC on The 16-Bit Fallacy: Why More Isn’t Always Better in Medium Format Cameras
  • JimK on Fujifilm GFX 100S II precision
  • Renjie Zhu on Fujifilm GFX 100S II precision
  • JimK on Fuji 20-35/4 landscape field curvature at 23mm vs 23/4 GF
  • Ivo de Man on Fuji 20-35/4 landscape field curvature at 23mm vs 23/4 GF
  • JimK on Fuji 20-35/4 landscape field curvature at 23mm vs 23/4 GF
  • JimK on Fuji 20-35/4 landscape field curvature at 23mm vs 23/4 GF

Archives

Copyright © 2025 · Daily Dish Pro On Genesis Framework · WordPress · Log in

Unless otherwise noted, all images copyright Jim Kasson.