RAW vs White balance

Started Nov 20, 2006 | Discussions thread
Jonas B Forum Pro • Posts: 14,596
Re: RAW vs White balance

edhannon wrote:

The idea that WB may effect RAW files caught my attention. It
would be great if I could reduce red channel saturation in tungsten
light by changing white balance.

So I wanted to see it myself. Unfortunately I have a *istD and the
histogram Java program is for those models that compact the Raw
file by using the top 4 bits of the 16 bit word.

It had been a long time since I have been able to play with writing
software, so I started a background project to implement the
histogram routine in MS Excel QBA. This way I would have more
flexibilty in analyzing the results.

It is hard to stop once you get going on a project like this ... so
now I have an Excel spreadsheet that has QBA modules that will not
onlly draw historams for the *istD but also create tone curves from
a series of "white wall" images. I plot the mode of the values in
the file. This is the most common value.

I did a white wall test early this morning before the sun came up
so I could use pure tungsten light. The results are below.

The first curve is from images shot with white balance set to
daylight and the second with white balance set to tungsten.

The differences between the curves is very small. What difference
there is I atribute to changing light conditions -- the sun was
coming out.

Clearly changing white balance will not reduce Red saturaton in
tungsten light.

Hi Ed,

I read your post with interest. It seems as you are back to the old idea about using a light blue filter then to keep the reds within limits?

When plotting the data, where from do you get the numbers? I guess you run the file through a raw converter (unless I missed something essential in your post)?

Can you elaborate a little? I'm thinking of a situation where you tell the raw converter that you used the Tungsten setting for the picture. Then the converter adjusts accordingly and your data shows just what came out from the converter, not what is in the raw data stream? Judging from your earlier posts I don't think you missed anything but I'm still interested in what the workflow was, exactly, when you got these curves. If you got the time.



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