Gear Talk > EOS Bodies - For Video
5D Mark III Magic Lantern wish list poll
psolberg:
I wish they would improve the soft output of hte 5DIII to match the GH2. unlikely since it seems you have to remove the OLP to get any sharpnesss out of hte 5DIII video.
HurtinMinorKey:
Does anyone know where you can download a editor that can edit Canon firmware ?
peederj:
--- Quote from: psolberg on April 30, 2012, 07:23:14 AM ---I wish they would improve the soft output of hte 5DIII to match the GH2. unlikely since it seems you have to remove the OLP to get any sharpnesss out of hte 5DIII video.
--- End quote ---
I have never seen any evidence that OLPF removal, which will only affect the 22MP image directly, affects the 2MP video in any significant (positive) way. That's a false meme that has even bled into the stills people's vernaculars, and it should be crushed until and unless reproducible, verifiable evidence (i.e. resolution charts, moire charts, etc.) is presented.
The damage to the video is done in the digital downscaling, and if ML can hack into that and provide a better method, the 5D3 will be unleashed. If Canon really wanted to protect the 1DC and C300 from the 5D3, they will have made that inaccessible.
herbert:
--- Quote from: HurtinMinorKey on April 29, 2012, 07:54:49 PM ---
--- Quote from: syder on April 29, 2012, 06:48:53 AM ---When expressing chroma subsampling ratios the 4:2:2 doesn't refer to primary colours as G:R:B, it's Y:Cb:Cr which refers to Luminance (Y) and two colour difference components Blue Difference (Cb) and Red difference (Cr)
--- End quote ---
I think that they are one in the same (G:R:B and Y:Cb:Cr) in this application, but I'm not certain.
--- End quote ---
The 4:2:2 is a type of chroma sub-sampling.
Since the human eye is more responsive to brightness than to colour it is possible to save space when storing an image by storing more brightness values than colour values. This is done by converting the RGB colour space to Y:Cr:Cb. The colours (Cr,Cb) are then sampled less than the brightness (Y) when the image is saved.
Note that the Y:Cr:Cb colour space can be converted back to RGB (it is simply a different 3-dimensional representation of the same data). Missing Cr:Cb values are filled in from surrounding values and then each pixel is converted back. This is done when viewing the movie.
Check out the Wikipedia article that has a few picture showing how the image stored in different sub-sampling schemes looks:
http://en.wikipedia.org/wiki/Chroma_subsampling
--- Quote ---The subsampling scheme is commonly expressed as a three part ratio J:a:b
J: horizontal sampling reference (width of the conceptual region). Usually, 4.
a: number of chrominance samples (Cr, Cb) in the first row of J pixels.
b: number of (additional) chrominance samples (Cr, Cb) in the second row of J pixels.
--- End quote ---
From this you can appreciate the 4:2:0 is worse than 4:2:2 since the former will only change colour every other horizontal line. Both will change colour every other vertical line. The holy grail is 4:4:4 since that does not throw any information away. If also takes up more space.
The second factor in quality is how many bits are used to store the data. Canon DSLRs use 8-bits (values from 0-255). The Cinema cameras use 10-bit (0-1023) or 12-bits (0-4095) so get a lot more gradation of tone. This also takes more space.
I believe the combination of sub-sampling, bit-depth, image size (e.g. 1920x1080) and frame rate (e.g. 24/s) are all combined to create a bit-rate for the movie. This is how many numbers are passed through the system per second. It is this final number that states the overall quality of the system and also the type of storage media requirements involved.
HurtinMinorKey:
--- Quote from: herbert on May 02, 2012, 08:04:35 AM ---Note that the Y:Cr:Cb colour space can be converted back to RGB (it is simply a different 3-dimensional representation of the same data). Missing Cr:Cb values are filled in from surrounding values and then each pixel is converted back. This is done when viewing the movie.
--- End quote ---
This is what I was saying, they are the same essentially in terms of the relevant data they carry, with maybe a affine transformation between them. Which is why I thought that MAYBE, the Bayer pattern, which is like a native 4:2:2 sample, might have something to do with preventing a 4:4:4 output, without serious processing/interpolation.
Also, 8bit is nice, but since monitors are only 8-bit(RGB totalling 24) the extra bits are ONLY use full in post. Theoretically the extra-bits don't give you a better picture, if you have the proper white-balance/exposure to begin with.
I think I've read that wiki article 10 times, great stuff.
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