Reading an Imatest Plot: Tonal Response, White Balance, and Gamma

March 21, 2017
June 27, 2017

Learn how to use an eSFR-ISO chart in the interactive Rescharts module in Imatest to measure tonal response, gamma, and white balance of a camera.

2 thoughts on “Reading an Imatest Plot: Tonal Response, White Balance, and Gamma

  1. i have little confuse .
    what do log(pixel level / 255 ) mean ?
    and 0 -0.2 -0.4 -0.6 …. ?
    could you explain ?
    please .

    • Hi Mark

      Pixel level ranges from 0-255 for 8 bits per pixel images (such as 24bit RGB color images). Levels range from 0-65535 for 16 bit images. We divide by the maximum of the range to obtain a normalized pixel level from 0-1.

      Log means Log base 10, so log(x) is equal to the exponent of 10 required to obtain x, I.e.: log(1/255) = -2.4065, log(255/255) = 0. This is the same thing as saying 10^-2.4065 = 1/255, 10^0 = 1. Hope that helps! -Henry

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