Soft-Proofing and simulation¶

Proofing, or simulation or soft-proofing, consists of simulating the various color space conversions that may occur on the image before reaching the end user, in order to verify the final conformity of the colors without having to export, print, calculate the project to test, but live on screen.

Indeed, if the display space of the screen cannot be changed and must be that provided by the manufacturer (sRGB in the majority of cases), the delivered project will not necessarily be in this space.

Let’s take the example of a project delivered in standard HD video which will ultimately be exported to Rec.709, the work on the image being done in a linear RGB space. In this case, when working on the image, images are displayed after a conversion from Linear RGB (working space) to sRGB (screen space).

Work: Linear RGB → Screen: sRGB

It may be useful in this case to introduce an intermediate conversion to Rec.709, final output space, to check the result. In this case, a second conversion then occurs to return to the sRGB space of the screen. This conversion would also take place when reading the exported file, in the same way, and proofing thus makes it possible to test the colors in real viewing conditions.

Work: Linear RGB → Output simulation: Rec.709 → Display: sRGB

In the same way, it’s possible to use this technique to preview and simulate the transformations that colors will undergo during much more radical changes in color spaces, for example for printing, and therefore transition to a subtractive space like CMYK; in this case, this is an actual simulation, as the output space cann’t be reproduced exactly by the sRGB space of the screen.

Work: Linear RGB → Output simulation: CMYK → Display: sRGB