• 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 / Sequential color space conversions at varying precision

Sequential color space conversions at varying precision

October 8, 2014 JimK Leave a Comment

I am now spreading my color space net to include a wide variety of possible RGB working color spaces. I picked 13 for testing:

  1. IEC 61966-2-1:1999 sRGB
  2. Adobe (1998) RGB
  3. Beta RGB
  4. Bruce RGB
  5. CIE RGB
  6. ColorMatch RGB
  7. Don-4 RGB
  8. ECI RGB v2
  9. Joe Holmes’ Ektaspace PS5
  10. PAL/SECAM RGB
  11. ProPhoto RGB
  12. SMPTE-C RGB
  13. Wide Gamut RGB

If you’re curious about the details of any of these, go to Bruce LIndbloom’s RGB color space page and get filled in.

I wrote a program to take an image of all 16+ million possible colors in SRGB and map it into an sRGB image that is within the gamut of all of the above color spaces. More on how I did that in a subsequent post.

Then I wrote a program to convert the image to sRGB, the first on on the above list, and convert that image to all the other color spaces on the above list in list order. Then it moved on to the next color on the list, and did the same thing again. And again, and again, until it reached the bottom of the list. It skipped the conversions to the source color space. That gave me 13*12, or 156 conversions. I set up the program so that it would either leave the image in double-precision floating point after the conversions, or quantize it to integers whose precision I could choose. Then I computed some stats.

Here’s the result of leaving the converted images in 64-bit floating point:

16MseqFP

Some conversions produce greater errors than others, but all the errors are very small, being much less than one-trillionth of a DeltaE

If we convert each image to 16-bit unsigned integer representation after each conversion, we get this:

16Mseq16bit

The errors are all under one-thousandth of a CIELab DeltaE.

With conversion to 8-bit unsigned integer representation after each conversion:

16Mseq8bit

Now we have mean errors of 1/3 of a DeltaE, and worst-case errors of about 2 DeltaE. You definitely want to be careful when converting color spaces if you’re working with 8-bit images.

I expected that some RGB color space conversions would be more prone to error than others, and that turns out to be the case. What surprises me is how small the differences are — one binary order of magnitude covers them all.

The Last Word

← Color space conversion errors with ProPhoto RGB — 15 bits Chained color space conversion errors with many rgb color spaces →

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

  • JimK on How Sensor Noise Scales with Exposure Time
  • Štěpán Kaňa on Calculating reach for wildlife photography
  • Štěpán Kaňa on How Sensor Noise Scales with Exposure Time
  • JimK on Calculating reach for wildlife photography
  • Geofrey on Calculating reach for wildlife photography
  • JimK on Calculating reach for wildlife photography
  • Geofrey on Calculating reach for wildlife photography
  • Javier Sanchez on The 16-Bit Fallacy: Why More Isn’t Always Better in Medium Format Cameras
  • Mike MacDonald on Your photograph looks like a painting?
  • Mike MacDonald on Your photograph looks like a painting?

Archives

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

Unless otherwise noted, all images copyright Jim Kasson.