@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.

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.

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.

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?

@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.

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.

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.

For 4k to be downsampled to something equivalent to 10-bit, it will need extensive dithering.

What kind of dithering? Did you read link above to understand from where 10bits can come from?

I already posted this link - http://www.personal-view.com/faqs/camera-usage/general-camera-usage-faq#more-megapixels-is-worse-isn-t

Scaling a 4k image to 1080 will improve colour rendition to a close approximation of 4:4:4 colour sampling but 8 bit is 8 bit and stays 8 bit. Bit depth is a measure of how many luminance samples there are between black and white limits. Colour sampling is the resolution in the spatial plane i.e. X/Y axis. So we will see an improvement in colour resolution but not bit depth. Banding will still be an issue.

This is not about compression, I mean it is, but not in the sense that software that would do the up-sampling or whatever the proper term would be, must create missing information out of nothing, it just rearranges the existing color information into new pattern with more color resolution. So the up sampling uses the information that would be thrown away in simple down-scaling (I am over simplifying I know), and ads +2 and +4 to Cb and Cr to make 444. Luma is 4 anyways.

Am I even close to the logic behind this process?

This was discussed a few years ago. Extract below from http://www.ambarella.com/docs/1080p60.pdf ( it's no longer online and I can't find a copy)

"This creates the opportunity to use 1080p 60 4:2:0 60p at 8bits-per-sample as a unifying format for both contribution and distribution. This is the case because down conversion of 1080p60 4:2:0 at 8 bits-per-sample can deliver 4:2:2 with increased dynamic range (almost 10 bits) at both 1080i and 720p resolutions"

all analog signal is measured by wave. Can be square, but wave. The value of the pixel well is not continuous, giving a dynamic measure in time, interpreted by a wave in the ADC.

It is called flame topic, not bullshit topic, if you noticed :-)

Thing that you just said is very incorrect as you even do not understand that you are talking about.

And this

all analog signal is measured by wave.

Must be added to famous citations :-)

As I said, please READ SOMETHING and THINK before posting.