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the last word

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

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Archives for September 2015

Does reducing a7RII ISO decrease AF accuracy?

September 30, 2015 JimK Leave a Comment

A reader asked the following: …did you find that AF focusing in the dark conditions with a nominal ISO locked @ ISO100 works worse than ISO for example being way higher ? Good question. Only one way to find out. Start with an a7RII and a Sony 90mm f/2.8 macro lens. Proceed as follows: RRS… [Read More]

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Sony a7RII zebras

September 29, 2015 JimK 13 Comments

There’s a maxim in medicine: “If you hear hoofbeats, think horses, not zebras.” It means look for the most common maladies first. I’ve always liked that rephrasing of Occam’s Razor. What’s that got to do with today’s topic, which is using the zebra viewfinder display option in the Sony alpha 7R Mark II (a7RII to… [Read More]

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More on read noise and quantizing

September 28, 2015 JimK 3 Comments

A reader commented on the previous post: The real tough part of posterization is when a gradient is colored and you get hue shifts as the color channels step across bins individually. Can you redo this test with a color gradient, like maybe 0.6 0.8 1.0 relative values to the channels? Pleased to do so…. [Read More]

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Read noise and quantizing, again

September 28, 2015 JimK 9 Comments

About a year ago I wrote a post on how read and quantizing noise interact in a digital camera. I concluded that, when the standard deviation of Gaussian read noise exceeded one-half the least-significant bit (LSB), the read noise provided sufficient dither that further increases in ADC precision would offer no increase in average digitizing… [Read More]

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Cruising with the Sony a7RII – summary

September 27, 2015 JimK 13 Comments

The spirit may move me to comment on one or two narrow aspects of my photographic journey from Sitka to Seattle, but I think it’s time for me to summarize my experiences. If you want to start this report from the beginning, look here. A little context: as I said at the outset, I eliminated… [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

  • 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
  • Ivo de Man on Fuji 20-35/4 landscape field curvature at 23mm vs 23/4 GF

Archives

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