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the last word

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

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Archives for 2025

Visualizing aberrations — caveats

June 23, 2025 JimK 2 Comments

For the past couple of weeks, I’ve been working on a simulator to assist in visualizing the effects of lens aberrations. In the interest of computing speed and programming effort, I’ve had to make a lot of compromises, but I hope it will be useful. I’ll be presenting results soon, but first I’d like to… [Read More]

The Last Word

More Than Exposure: Understanding Total Light on the Sensor

June 16, 2025 JimK 2 Comments

Photographers often talk about exposure. It is one of the most familiar concepts in photography. But there is another important idea that hides just behind the curtain: the total amount of light that lands on your sensor during an exposure. Understanding the difference between exposure and total light can clarify a lot of confusion about… [Read More]

The Last Word

Diffraction and the Airy disk diameter

June 6, 2025 JimK 3 Comments

The Airy disk is the central bright region of the diffraction pattern produced when a point source of light passes through a circular aperture, such as a camera lens or a telescope objective. It represents the fundamental limit of resolution imposed by diffraction in an optical system with a circular pupil. When light passes through… [Read More]

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A Modest Proposal

June 6, 2025 JimK 9 Comments

It is a melancholy object to the informed photographer, when traversing forums, YouTube comment sections, and even certain articles in the photographic press, to behold the frequent complaints of confusion arising from the concept of photographic equivalence. These complaints, sincere and repeated, inform us that equivalence is too complicated for the modern mind, too abstract… [Read More]

The Last Word

Do Raw Developers Use the Embedded JPEG as a Color Reference?

June 5, 2025 JimK 5 Comments

In a recent thread on DPReview, someone made an interesting claim: that some raw developers use the embedded JPEG in raw files as a reference for color. The idea seems to be that the raw converter might read this in-camera-rendered preview to guide or inform its own color processing. That assertion caught my attention, and… [Read More]

The Last Word

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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

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  • Christopher Roberton on Fuji 120/4 GF at 1:1 with tubes — visuals
  • Pieter Kers on Visualising lens aberrations — one at a time, Siemens Star
  • JimK on Visualizing aberrations — caveats

Archives

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