Julia Borg's white balance tip

Started Mar 3, 2007 | Discussions thread
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Pedro Dias
Pedro Dias Senior Member • Posts: 1,090
Julia Borg's white balance tip

I went out today to try out Julia Borg's tip for more accurately match the histogram of the internal jpeg with the RAW image that I always shoot.

I am using windows Vista, and had no way of passing the uniwb file onto my camera. Instead, I downloaded and used the JPEG (looks like a McTabeth color table) that was in the post, passed it over to my D200 and loaded it up onto my D1 custom white balance setting.

The easiest way to test Julia's theory, was to take my pitch black dobermann outside in the snow, cloudy weather, and here's what I did:

I shot a couple of shots directly against the snow, adjusting the histogram so that it ends right at the right end of the scale. This was about EV +2.0 at ISO 800.

I needed at least that much to get detail out of my dog's fur.

Now, shooting and working with the histogram "in situ" was fun, I was getting perfectly exposed images every time, nothing out on the right side, and the black side was fairly pushed to the right - very well! Happiness is near!

But, coming home, I discovered two things:

1. once loaded in NC4.4, the RAW histogram shows something completely different - the image is not perfectly exposed, but it is overblown, and not only that, the histogram suddenly stops to the right, but not on the far right.. let me illustrate:

There is a VERY steep curve on the right, almost a "chop" as you would expect to see on an overblown jpeg. Double-checking again in the camera shows me a near perfect exposure, where the whites tone out alot less harshly.

In terms of noise, reducing the exposure by a full stop simply elliminated noise. It was magic - noise completely gone (cept for some luma stuff, of course) - but, detail was still not good enough in the fur areas, and raising the shadow areas brought back some noise, not too much though, but enough:

You can now clearly see the "chop-off" on the right side of the histogram.

The darkness of the image can be corrected to some extent by setting white and dark points, however, this creates a nasty effect in the snow, where it kinda looks like it does when you look at an image of clouds on a screen with 16-bit color depth - the tones are completely lost.

I wonder what I am doing wrong. The images also have the added "feature" of not being able to be converted at all in ACR or any other RAW converters for that matter - they all get a horrendous green cast to them.

I am sure that there is something in the process that I have completely misunderstood, or forgot to do. I'm just not sure what.

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