Luminous Landscape Forum

Raw & Post Processing, Printing => Digital Image Processing => Topic started by: papa v2.0 on December 03, 2007, 09:56:28 pm

Title: pure raw
Post by: papa v2.0 on December 03, 2007, 09:56:28 pm

are anybody doing pure raw

from un demosicased files etc


before white balancing etc  

or are you  three channels' then white bal

interested to know

Title: pure raw
Post by: John.Murray on December 04, 2007, 01:15:01 am

Perhaps you could define your terms and workflow for us?

Title: pure raw
Post by: 01af on December 04, 2007, 06:32:03 am

'Pure raw' is what's inside your raw files. It's nothing you can look at; it's just a giant heap of numbers.

As soon as an image was created from those numbers, it's not raw anymore.

So 'pure raw' is a concept that does not exist.

-- Olaf

Title: pure raw
Post by: Graeme Nattress on December 04, 2007, 08:19:45 am

White balance needs demosaiced data to work. Actually, you could white balance raw data using just multiplies on the pixels that represent red, green and blue, but most modern white balance doesn't work on a simple multiply.

Modern white balance uses a 3x3 matrix, so you need to  know the RGB for each pixel. That means it must be a post-demosaic process.

Normally the order of operations is:

linear raw data
demosaic - in software, usually a highly adaptive algorithm
white balance - 3x3 matrix
conversion to output colour space - 3x3 matrix
tonal mapping / curves - look up table

All the 3x3 matrices used can be concatenated together.

You can actually do more than the above, but that's the simplest that works and works well. (I write RAW conversion software BTW.)

Graeme