WB analysis:intensity values vs. uncalibrated od?



I’m analyzing some WB with ImageJ gel analysis tool but I quite new to this. I’ve reading ImageJ guides but still I’m not sure about some details. When I plot the profiles of each lane, ImageJ by default plots the pixel intensity along the lane but in the gel analyzer options we can set Uncalibrated od, which seems to transform this intensity values in relative optical density values by the following formula: Unc. OD = log10(255⁄pixel value) (https://imagej.nih.gov/ij/docs/guide/146-30.html#sub:Calibrate… After reading the guides and a few tutorials, I cannot find a clear explanation of when should we use each of these options and I guess I’m missing some important information to be able to understand.
Thanks in advance!