Thief the Black Parade gamma

Anyone else find the gamma needs to be tweaked for individual missions?

The black parade is too dark with the slider in the middle for me, so I found the perfect level and saved it on note pad to copy and paste when I need it. However I found that the third mission has shadows that are much "weaker" than the first two missions and i had to make adjust it and put it in notepad. Mission four is about the same as the first two. Mission 5 - 7 and 9 need an individual adjustment as well. Is this because the levels in the game were made by different level creators, and thus don't share consistency with world illumination (or whatever it is called)?