[Bf-vfx] On Format Woes

[Andrew Hunter]

Hey Peter,

On Sun, Apr 8, 2012 at 9:17 AM, Peter Schlaile <peter at schlaile.de> wrote:
> Hi Ton,
>
>> I'm personally a bit concerned about the image quality itself  - the amount of noise is disturbingly high. I would expect a nicer signal-noise ratio.
>>
>> I also like to figure out how sony stores a frame in 10 Mbyte, and exports that to 50 MByte files. We probbly have to do more testing. :) And talk to sony i guess!
>> (There seems to be a F65 SDK too, but I didn't check on that yet)
>
> you should actually be worried about that (at least a little, see
> below) :)
>
> My observations so far:
>
> * I've taken a look using a hexeditor and mxflib on the MXF-files you
> provided.

Are these the files provided on the blog? Sabastian didn't mention if
they were the camera origianl raw files contained in an MXF or the SR
codec.

[...]
>
> Raw sensor data should accumulate to:
> 4160 x 2204 x (1 Green + 1/4 Blue + 1/4 Red) x 16bit = 27505920 bytes.
>
> Roughly a compression ratio of 1:3. There is still hope, that this can
> be done losslessly or at least with very mild compression.
>
> For comparison: a RED encoded 4k RAW frame has the following specs:
> (Taking the 4k-ColorDots-T8 from bealecorner.org)
>
> File size: 1292268 bytes
>
> Raw sensor data:
>
> 4096 x 2304 x (1/2 Green + 1/4 Blue + 1/4 Red) x 12bit = 14155776 bytes
>
> This is a completely different story, namely a factor of round about
> 1:11. (That said: recent RED cameras can be tuned to 6:1 in 4k
> resolution).

On the Red Epic, a compression ratio of 3:1 is possible at 5k. The Red
One topped out at Redcode 42, equivalent to about 7:1

> Looking at ARRI Alexa frames BTW reveals, that they store indeed simple
> uncompressed data 1:1 no strings attached. It's a pity, that this camera
> only delivers 2k - at least, it does it totally uncompressed.

Are you referring to ProRes, DNxHD or ArriRAW output?

> So I see three ways to go:
>
> a) ask Sony, if they will clarify this issue and/or provide us with a
> SDK.
>
> b) ask ARRI, if they have a 4k Alexa in the pipeline (despite the
> statement within their FAQ which tells us otherwise...) :)
>
> c) ask RED, if they ... wait, is there any point in doing so?
>
> Seriously: even the Wavelet encoded RED files look very nice. They do
> pretty clever difference encoding for the R and B-channel (they are
> compressed relative to the G-channel).
>
> On the minus side is there deliberate codec obfuscation on current
> firmware releases, which is a pity, when used within an Open Movie
> Project.
>
> The Sony F65 should nevertheless deliver the better picture quality
> regarding the used codec compression ratio (keep in mind, could be
> lossless, we don't really know.), the higher bit depth and the better
> resolution within the green channel (which is very important since Green
> has the strongest contribution to the luminance channel).

> At least in theory, since there is a lot more to picture quality than
> the codec in use.

Agreed! Image quality has much more to it than merely bit depth and
spacial resolution. The color gamut and perceptual sharpness are
equally, if not more, important. Zeiss has a good summary of the
perceptual sharpness of photographic systems, archived here:
http://www.zeisscamera.com/doc_ResContrast.shtml

The popularity of the Alexa is proof of that. Roger Dekins noted that
it's ability to render color gradations under lighting that film would
have saturated was part of his reason for claiming he was done with
film. The fact that it outputs "only" 1080p doesn't really factor in
to it. To quote an IA667 focus puller friend, the Alexa is the best
camera for episodic TV production he's ever seen. Everything about it
"just makes sense".

> <troll mode>
> Have we already talked about the type of lenses, you intend to use for
> Mango :) ?

The photos from the blog suggest Leica. Zeiss vs Leica vs Cooke! Fight!

Sincerely,

Andrew