Posted by
Adrian Daerr-2 on
Mar 27, 2008; 10:57am
URL: http://imagej.273.s1.nabble.com/RV-Question-for-8-bit-grayscale-values-tp3696737p3696738.html
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> For an optical density calibration, when you are capturing 8-bit grayscale
> images (values from 0-256), it is supposed that the darkest standard picture
> corresponds to the lowest value. In our case that is not true, the darkest
> standard picture is shown as the clearest picture and the mean value is the
> highest. It seems that the camera is acquiring the picture in “negative
> mode”. Does it make any sense? Does anybody know how to change/solve it?
Both conventions exist (the black=0/white=255 convention is the most
common for video acquisition because a pixel integrates light, and so
its value corresponds to the intensity; the black=255/white=0 convention
is more common in printing, because here people are used to indicating
the amount of toner when printing on white paper). Likely your
acquisition hardware/software follows a different convention from ImageJ
(ImageJ's predecessor NIHImage had the opposite convention, if I recall
correctly...).
Simple solution: just invert your movie after acquisition
(Edit->Invert). Otherwise find out how to modify the acquisition process...
best regards,
Adrian
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