Hi,
I have attached links to an extremely simple scene showing the behaviour I’m getting and I maybe did not explain myself correctly the first time around. I’d be very grateful if someone would try it to confirm it’s not just something at my end.
Auto Exposure in camera settings (render dialogue) is set to on and this makes the selected object render very much brighter, making it unusable.
Without Autoexposure there is no issue.
All it’s necessary to do is select a teapot - choose Render Mask Selected and hit render - swap between Selected and None and you will hopefully see exactly what I see and
the same as in the images here.
Thanks all 
Hello,
Actually this is kind of expected. The automatic exposure works by examining what the camera sees during the light cache pass. When you use the Render Mask feature effectively the camera doesn’t see anything but the selected objects. This makes the automatic exposure result different from the one you get if you render everything. The same applies also when you render a region.
If you want to use the auto exposure and then render mask or render region - you should do the initial render of the whole image and after that use the “Transfer to camera(s)” button in the render setup. After that you need to turn off the auto exposure. That way the exposure will stay constant no matter the region/object you select.
Best regards,
Yavor
Hehe…well that has resolved 4 days of head-scratching. Thank you very much Yavor. This indeed solves all issues in both cases and I’m sorely tempted to jump on a plane with a case of beer for you 
Glad that this resolves your issue
We should probably add some kind of a warning in the log for cases like this.
I think the thing that threw me is that I’m mid-job (I know, I know :p) and was testing the Auto-exp/WB and although I saw the ‘transfer to cameras’ option I didn’t relate it to the issue, so ignored it from the tests.
16 hour days don’t help when trying to figure out new things. Still, all good now and knowledge increased
