I just posted results from some testing I did on my panel on the PN51F5300 thread but I think it would be good to share the results here as well.
I was mainly interested in looking at 2 things:
- Impact of APL on black level luminance. For this I used the ColorHCFR small and Large APL patterns on the AVSHD709 disc and compared against all black screen readings
- Impact of Black Optimizer set to Dark Room v/s Auto
Below is the raw data from my tests.
Full Black Screen
0% AVSHD709 ColorHCFR Small APL
0% AVSHD709 ColorHCFR Large APL
Black Optimizer Dark - 12% Window size
120.009136 cd/m2 (100% Gray - i.e White)
0.006947 cd/m2 (0% Gray)
Black Optimizer Auto - 12% Window size, 100% Gray (white)
144.127510 cd/m2 (100% Gray - i.e White)
0.007023 cd/m2 (0% Gray)
As you can see from the readings above, The small APL patterns do not exhibit an appreciable rise in black level. However, for the larger APL pattern, I do notice an increase of black level from ~0.002 ftL to ~ 0.005 ftL which is consistent with ChadB's measurements.
I was also thrilled to note that the Black Optimizer setting of Auto does in fact boost peak luminance of 100% white to ~42ftL from 35 ftL
if BO is set to dark room. Moreover, this does not seem to degrade black level for all black scenes as both settings measured MLL of ~ 0.002 ftL.
Looks like I will now use Auto for daylight viewing as 42fL is I believe the max output this panel can produce (outside of Vivid mode) and it matches the peak luminance in Standard mode. I'll stick to Dark Room for night time viewing.
While there is some amount of "floating black" with my panel, I really don't notice it at all. Even at the higher APL setting, if I have 100% white on the screen in the image, the contrast ratio still works out to >7000 making it impossible for the eye to notice the slight rise in black level. There might be some edge cases where it may be noticeable to the discerning eye, but I just haven't seen it. What is far more obvious instead is the fact that blacks look really black when the image has any bright section in it (since our iris adapts accordingly)... but then if the screen transitions to an all black or very dim scene, suddenly the blacks don't melt into the bezel any more as our iris adapts again for the lower light. So in that sense, there is a perception of changing black levels, but it has more to do with the limited dynamic range of our eyes than the TV.
I do know that floating blacks were more evident and visible to me when I did not have brightness set correctly to get rid of the green dithering haze on screen for black screens. Once I set my brightness optimally, I have never noticed an issue of floating blacks.