Quote -  Hum
[http://http.developer.nvidia.com/GPUGems3/gpugems3_ch24.html

"For example, by convention, all JPEG files are precorrected for a gamma of 2.2."!!!!
:cursing:
In pp, cheked gamma correction =gamma correction of precorrected gamma texture= gamma error

Solution:not to save in jpeg format, using a format  nondestructive and no gamma precorrected ex. png,. tif; hdr, and other
Or, use gamma inverse node in materials room

Sorry for my bad english

Ps:Jpeg=inadapted format for the 3d applications
](http://http.developer.nvidia.com/GPUGems3/gpugems3_ch24.html)

Kalrua, thanks muchly for the link.  Gamma correction is explained very clearly in this article.  I also love the witty title "The Importance of Being Linear".  Oscar Wilde has always been my favorite playwright.  I simply cannot resist laughing each time I read or watch his famous play "The Importance of Being Earnest".