Differences in surface brightness for galaxies

Does a linear relationship exist between the numerical difference in surface brightness between two galaxies vs the percent difference in brightness?

For example, lets assume we have two galaxies - one with an SBr of 12.5 and the second 12.6. Let's assume that it works out that the 12.5 is 10% brighter than the 12.6.

Now consider a third galaxy with an SBr of 13.0. Would the 12.5 be 50% brighter than the 13.0?

Would the 12.5 then be 100% brighter than a 13.5?

Or is the relationship between the numerical difference in SBr and visual brightness nonlinear?

If so, how can I compare them?


Thanks........Mike