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You are here: Home / The Last Word / Sharpness testing, part 19

Sharpness testing, part 19

November 24, 2013 JimK 2 Comments

I performed a test of the D800E and the Nikon 400mm f/2.8 lens with the oscillocope time base set to 1/2 second per division. Here is the result magnified by a factor of 6 in the vertical dimension:

d800 400 no lv 0 sec delay h half second

Same second-order underdamped vibration. The time constant seems to be even longer than two seconds, more like three. The initial amplitude is about 18 pixels peak-to-peak (PP). To get it to one pixel PP, we need three time constants, or 9 seconds.

By the way, the head isn’t causing the vibration. I tried the Arca Cube and got the same results.

The Last Word

← Sharpness testing, part 18 Sharpness testing, part 20 →

Comments

  1. Jack Hogan says

    April 6, 2014 at 9:57 am

    Hi Jim,

    Great idea that of the oscilloscope for vibration testing. You may be able to make the resulting images more readable by white balancing the raw data: if you are using DCRAW try -d -4 -T -r (r,g,b,g multipliers to make all channels about the same value on the trace).

    Jack

    Reply
    • Jim says

      April 6, 2014 at 10:30 am

      Thanks for the tip, Jack. I don’t use the raw values any more, finding that using interpolation ro res up Lr converted images gives better visualization:

      http://blog.kasson.com/?p=4674

      Jim

      Reply

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