I have to admit that I was wrong..
I used HCFR heavily today and examined the BT1886 functions and options and I realise that I was using it wrong.. and that the experts here where right.. BT1886 takes the black level performance of the screen into account..
The Calibration software will plot your own BT1886 gamma curve that fits perfect to your display (and also to your gamma that you chose, you can chose for example a gamma 2.0 curve for a bright room or 2.4 for a dark room, or 2.3)
A short explanation and I might have an idea why you did not get the right gamma curve with your input black level..
At least with HCFR, the software needs following information: The Black level, the effective input offset at 50% (that is your actual gamma at 50%,) and the max light output.. In my case it is somehow fixed to 120 nits...
The software will then plot you a gamma curve for your display with your specific black level, and your gamma at 50% stimulus.. So you should just make one gamma reading with your prefered gamma and then you have all the information.. Black level and at what gamma your tv ends up in the 50% area and above..
In my case there was also a trick thing with the black level.. I had to type 0.1 rather then 0,1 to get the number accepted..
With my plasma and a really bad black level I could not use my chosen darkest gamma, so I went over to the stock 2.2 setting.. With a darker gamma I would have needed to increase the darkest parts much more, but this set has no detailed gamma controls..
Very interesting.. and also very helpfull, because the BT1186 shows you the way, you can try different gammas and you see where you end up, what you need to change and maybe if you just cant get close with this stock gamma..