  # Kolen Cheung

5

## Everything posted by Kolen Cheung

1. Does anyone know the fps of the 24p in A7 and A7R? I didn't find this information in the manual and from my A7 and A7R, the footages show as 23.981 fps in FIlm Convert. Thanks.
2. A quick question. Does it have a 30 minutes limit in the US version? Thanks.
3. The Math is easy to explain. First, 4:2:0 means it has half of the resolution in both directions in the chroma channel. So if we downsample the resolution to a half, we have full color information in both directions, hence 4:4:4. Second, originally the luminance has full resolution and are 8 bit. We can consider 8 bit precision means there are 256 possible values, and as each of them are precise up to an integer, the absolute error is 0.5. Averaging 4 pixels will divide the absolute error by 4, hence 1/8. To make it an integer, we will multiply it by 4, hence 10 bit. Another way of saying it is there are 256 possible values for each pixel, adding the 4 pixels together make it 1024 possible values, hence 10 bit.
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