RAW vs White balance

Started Nov 20, 2006 | Discussions thread
GordonBGood Veteran Member • Posts: 6,308
Re: I don't believe it unless you tell me...

Dark Mist wrote:

I did follow what the thread is about. I'm just unsure how the
histogram gets generated from the RAW data. It seems to me that
some software must be used to read the raw file and make the
histogram. Even the histogram display on the camera's LCD is a
software interpretation of the RAW data held on the memory card.

The software works as follows:

1. Find the start of the raw data.

2. For all the rows and all the columns determine what colour channel the reading will be binned against from the Bayer array of the pattern such as:
RG
GB
repeated horizontally and vertically as for the Pentax cameras.

3. Uncompressed/Unpack/otherwise read the 12 bit data (again in the case of Pentax).

4. According to the value read, increase that bin number for that colour by one (all bins having been originally be initiallized to zero counts).

5. When all rows and columns have been read and binned, display all the bins (values) across the horizontal axis for each colour, with the colours being the logical or of the combinations of colours (ie additive colours) and the height proportional to the number if times the bin was increments.

That's a raw data colour histogram with no processing and that's what was produced here. If you read Java, the source code was provided with the program and one can see that this is what's done.

Regards, GordonBGood

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