If the 4k 8-bit image is properly dithered, the downscaling will lead to a smooth gradation equivalent of 10-bit.

Logic :-) As it is used in exactly reverse situation were you want to use limited values to represent something close to original. One of extreme cases is representing grayscale image using only b/w :-)

If you look at thin in reverse - converting high res dithered b/w image into grayscale (and read my link, yes link does not have anything about colors, but it explains why DR range in bigger after rescale) you'll understand were additional bits come from.

I just wanted to point out that it will be an inferior 10-bit compared to one diverged from an actual 10-bit source.

If you'll had source 4K 10bit in AVC file it could be cool. But. Most of this new bits will be quite noisy. Yes, in ideal noiseless sensor it is good advantage, not so much in 4K on m43 sensors.

@Vitaliy_Kiselev, with all you logic, please let me know how can you extract the 10bit dynamic range from a 8bit source? I mean "push" dynamic range in post, I mean get juice from the clipped highlight and the black darkness. Please don't tell me to "light the scene properly" or "get the right exposure", we know that even the right exposure have its limits, and some light are not 100% controlled (sun for example). Please, allow me to understand how these extreme dark "blacks" or clipped "whites" can be pushed, if they have only 8bit depth? From where this retrieved data will come from, if they nearby pixels from the 4k source are also 8bit darkness or 8bit clipped white? With 10bit data I can retrieve some over or under exposure parts because the elastic dynamic range of the 10bit. Let me really know how can you do that from 8bit? I already read all your recommend links and have found nothing about it, please let me know how to do it.

So tell me if I understand this right. 8bit 4k downscaled to 1080 yields a 444 image with "virtual" (for lack of a better term) 10 bit? This virtual 10 bit is good but can be expected to be noisier than native 10 bit?

with all you logic, please let me know how can you extract the 10bit dynamic range from a 8bit source? I mean "push" dynamic range in post, I mean get juice from the clipped highlight and the black darkness

Please understand, I can't fix problems with school math. And it is basic simple school math. Nothing to do with highlights and darkness :-)

Please just read link with buckets analogy, it has ALL you need (except working frontal core).

8bit 4k downscaled to 1080 yields a 444 image with "virtual" (for lack of a better term) 10 bit? This virtual 10 bit is good but can be expected to be noisier than native 10 bit?

Nothing is virtual, it is all real.

You could have a very high DR camera that only shoots 8 bit and a very low DR camera that shoots...heck....14 bit.

It all depends :-) If you are talking about raw for high DR you need good sensor, good ADC (say 12bit or 14bit low noise one) and also low noise. After you go from linear (almost) raw to the non linear space you can use less bits (by using human vision properties). Hence, yep, you can compress original high DR source into 8bit. Photo guys make even extreme HDR that look very weird.

@Ze_Cahue, I am guessing you don't record in 4K 8-bit and downscale to 1080p with your current equipment/workflow?

You will most certainly see problems when working with 8-bit, and keep in mind that you are likely also working with either uncompressed or much less compressed material from your external recorder than the internal codec.

@Ze_Cahue Your mindset is wrong and you are mixing together many variables. It's like saying a rock is heavy, and a car is heavy, so a car is the same as a rock. It makes no sense.

@Ze_Cahue. Of course, but my point is, if the processing is done correctly on the GH4, it will be possible to pull true 1080p 10-bit from a 4K 8-bit source-file. The reason is that the GH4 does the processing in 10-bit, and down-conversion happens last. If I worked for Panasonic, I could write code in 20 minutes that upon the downconverting, would make sure that for each pixel that will be present in the 1080p picture, I take the full 10-bit color information and split it out on 4 different 4K pixels, and make sure when you add them up, they match. This is VERY simple, and will work 100%. No need to worry about anything - you get TRUE 10-bit in a 1080picture (provided you also have a similarly smart resolution down-conversion process).

Whether Panasonic does this or not is another matter, but it can EASILY be done.

Question: aren't they getting to the point where Panny's prosumer cams like GH4 threaten to undermine their broadcast cameras? I mean what will the argument be? Buy the broadcast cams because they have a Tally light?

Ze-cahue, you still don't get it and I cannot explain it in simpler terms, so believe what you want.

@Ze_Cahue I am not a hard core programmer either, but I do write scripts and build complex 3d world models as well as work in audio. What tosvus is explaining is simple to understand and you appear to be assuming otherwise, I can also tell from your posts that English is your second language and maybe that is the problem. What he is saying is that the GH4 does the initial processing in 10 bit, therefore the intital 10 bit data is there in he first place in the GH4. So the gradation in highlights etc...will be there in 10 bit in the first place, and it downsamples to 8 bit...not the other way around...( 8 bit in the Camera trying to be 10 bit) and thats what you appear to be assuming, and others appear to assume this also. When you say "missing data" " all white pixels"etc...you are thinking it's initially baked in 8 bit in the GH4. He's saying its 10 bit FIRST...and it has to be (with or without the brick) so the DATA is there, its a simple matter of conversion etc..not hard to understand. Cheers