# In GIMP, how do I get the smudge/blur tools to work properly?

I use the smudge tool very often in GIMP while painting. Unfortunately, the algorithm tends to generate a much darker version of what the smudged color ought to look like. For instance, a normal smudge on GIMP looks like this:

But I want the smudged color to be a lighter yellow, sort of like this:

In general all smudged colors appear darker and I understand this has something to with GIMP working with sRGB colors as opposed to RGB. But I'd really like to know what setting I need to tweak in GIMP to correct the smudge algorithm (maybe blur too, but I use smudge much more).

[ I assumed sRGB takes the square roots of the original value, so when the smudge tries to average colors between two pixels 'a' and 'b', it takes $(\sqrt{a} + \sqrt{b})/2$, which is darker than $sqrt(a/2 + b/2)^2$. ]

GIMP 2.9 or higher

Image > Precision > Linear Light

GIMP 2.8 or lower

Image > Mode > Convert to Color Profile... > Select color profile from disk... > sRGB-elle-V4-g10.icc

You can obtain sRGB-elle-V4-g10.icc e.g. from here.

Source

I summarized what is discussed here as "radiometrically correct editing".

Linux stores color profiles in /usr/share/color/icc, however none of the preinstalled iccs I found there did the same thing as the linear light icc, so I think you do have to look on the internet for it. That directory might be a good place to put it though. Windows: C:\WINDOWS\System32\spool\drivers\color. Mac OS X: /Library/ColorSync/Profiles
• Regarding Mac color profiles: ~/Library/ColorSync/Profiles is better if you don't need to install it for all users of the machine, or if you don't have administrator access. – seaturtle Dec 1 '17 at 19:07