Howard Roll wrote:
...sensor data from a Bayer sensor you mean? In a 3 chip system the ratio is highly relevant and likely the source of most of this confusion.
Uncompressed bayer is 4:0:0 at the sensor level, Braw is more complicated.
A Bayer sensor as a ratio of red, green and blue pixels ?
There’s no red, green and blue in 4:2:2 or 4:4:4.
The first number is both the luminance, and the colour information of Green. Then the second and third numbers are the colour difference signals of R-Y and B-y, or the “UV” part of YUV.
They aren’t RED and BLUE, they are RED and BLUE when multiplied and subtracted with the Y signal. They have no brightness information.
In one system the luminance is encoded on the Y part of the YUV.
In RGB the luminance is encoded into all the channels. R, G and B all have luminance values.
This makes them fundamentally different and the use of 4:2:2 type terminology to talk about sensor data isn’t correct and creates false impressions.
Here’s a phrase from RED’s education site about Bayer sensors.
“Note: Those with a video encoding background may want to try and apply the 4:2:2, 4:1:1, etc. categorizations to a Bayer sensor, but this terminology is intended for compression methodologies and final images, not the sensors themselves. A 4K Bayer sensor is capable of producing full 4K 4:4:4 RGB files, for example; 4:2:2 is what could be applied to this file afterwards.”
https://www.red.com/red-101/bayer-sensor-strategyJB