As I said, Natron is displaying it instantly correct.
The Gamma Problem seems to have been a problem of my output application.
After I fixed that the regular Gamma 2.2 give the expected result.
I just checked the PFM file with Natron (free compositing software like Nuke) and there the image is correct. I also realized that the color representation in Natron is correct as in my exporting application. In XnView the image is too dark even I set a Gamma of 2.2. It looks like a wrong color ...
I just realized that (suddenly) PFM format is supported and I'm extremly happy about it. :) However, the format my application creates is vertically flipped. Question is, is this a :bug: or is my picture upside down?
I've attached a small sample file and just realized that XnView is not ...