Autograph’s engine works exclusively in linear space and uses 32-bits per channel, so that no information is lost during calculation and display. Pixels with very high luminance, greater than what can be displayed by a monitor but detectable by the picker, are kept.
In order to facilitate visualizing these extreme values, or contrarily, very dark pixels, the viewer has three functions that allow you to boost or reduce image luminance and chrominance:
- Gain (from -6 to +6 stops): acts like the diaphragm of a camera, letting more or less light into the lens.
- Gamma (from 0 to 5): changes the image gamma without modifying the perfectly black or white pixels, but only the intermediate values in this range.
- Saturation (from 0 to 4): decreases the saturation between 0 and 1, then increases it to 4.
To access these features, simply click on the diaphragm icon, located at the top left. This will unfold these three controllers.
The diaphragm allows you to globally activate or deactivate these post-processes. Each function also has a switch to remove the influence of one of these effects, which will gray out the associated value.
These post-processes are extremely useful to analyze HDR images or to better distinguish dark pixels.