Originally Posted by Tempest261
That's interesting that you still have the problem with 60 Hz content.
The strangest thing about this phenomenon is what I learned from David Mackenzie's reviews: engaging IFC effectively reduces these artifacts (it's still there but it's virtually nonexistent - you really need to look for it with picked materials from close distance and even then it's very minimal, nothing to worry about...).
The most disturbing thing is that I have no idea what IFC may do with progressive 60Hz input.
It does not change the panel refresh rate (neither on Mid or High setting), so there is no place for interpolated frames (unlike with 24Hz input and 48/60/92Hz panel refresh modes or 50Hz input and 60Hz refresh or even with interlaced 60Hz and 60Hz refresh).
However, it does increase the input lag (there is extra processing time, so there should be some extra processing...) and it does cause some other artifacts (similar to what you can see with 24Hz input + IFC engaged but much milder though).
So I have no idea what is really going on because it seems this (2011) panel with this driving system is able to visualize the images without this artifact in 60Hz refresh mode. However, you need to turn on something which not only causes other problems (different artifacts and extra lag) but should theoretically do nothing in this case (or do something but also change the panel refresh rate).
The best (actually the worst) I can think about: May be it treats the progressive 60Hz input as interlaced 60Hz and interpolates progressive frames again (and that's where the interpolation glitches are coming from but this is still no answer why it affects the dithering artifacts).
Or it activates some kind of processing we can't understand without explanations. (May be IFC introduces a lag of one frame to see what will happen and this helps to optimize the panel driving...? Ah, this is only a wild guess with zero facts.)
This story is confusing and make this phenomenon look like a stupid mistake on Panasonic's side. (Like they forgot about a small trivial thing or the left hand does not know what the right hand does...)