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the last word

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

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Archives for 2013

Sharpness testing, part 4

November 3, 2013 JimK Leave a Comment

Well, I thought I was done with the preliminaries, but it occurs to me that the standard deviation is going to vary linearly with exposure. I wrote some code to check that and correct for it. Then I came up with a way to simultaneously correct for overall exposure variation, and exposure variation caused by… [Read More]

The Last Word

Sharpness testing, part 3

November 3, 2013 JimK Leave a Comment

Before I deal with all the uncontrollable and semi-controllable variables involved in making actual test photographs, I did some simulation to make sure the target would work the way I thought it would under completely controlled, albeit unreal, conditions. I wrote this Matlab script: I ran it, and plotted the results. As expected, more low-pass… [Read More]

The Last Word

Auto-bracketing on the M240

November 3, 2013 JimK Leave a Comment

I went for a walk this morning, and took along what is becoming my constant companion when I don’t have anything particular in mind, but I think that a picture might jump out in front of me: the M240 with the 28mm Elmarit-M ASPH. No EVF. Small, light, and unobtrusive. The 28 is pretty soft… [Read More]

The Last Word

Sharpness testing, part 2

November 2, 2013 JimK 4 Comments

I wrote a little Matlab program to generate the targets: And, yes, all you Matlab experts, I know it can be coded a lot more efficiently, even by me. I wrote it this way so that any Java or C programmer could figure it out. Here’s what a close up of the first four layers… [Read More]

The Bleeding Edge, The Last Word

Sharpness testing

November 2, 2013 JimK Leave a Comment

While working with the firehouse pictures, I’ve come to the conclusion that some of them – maybe even most of them – aren’t as sharp as I’d like them to be, even with flat subjects. I’m not sure what the problem is, or even that there’s only one problem, but my current suspects are: Mirror… [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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