Comments on: Reading an Imatest Plot: Tonal Response, White Balance, and Gamma http://www.imatest.com/2017/03/reading-an-imatest-plot-tonal-response-white-balance-and-gamma/ Image Quality Testing Software & Test Charts Tue, 06 Jun 2017 17:20:33 +0000 hourly 1 https://wordpress.org/?v=4.8.1 By: Henry Koren http://www.imatest.com/2017/03/reading-an-imatest-plot-tonal-response-white-balance-and-gamma/#comment-40582 Tue, 06 Jun 2017 17:20:33 +0000 http://www.imatest.com/?p=18446#comment-40582 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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By: Mark Chen http://www.imatest.com/2017/03/reading-an-imatest-plot-tonal-response-white-balance-and-gamma/#comment-40581 Sun, 04 Jun 2017 16:15:13 +0000 http://www.imatest.com/?p=18446#comment-40581 i have little confuse .
what do log(pixel level / 255 ) mean ?
and 0 -0.2 -0.4 -0.6 …. ?
could you explain ?
please .

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