Dynax Digital Forums

Now I am being a PITA. Sorry. You will hate me..I am confused (again..still)   

Part A. You got me here Stef...this make no sense to me: the cursor over the red pen than each channel: red/ green and blue should give you a similar if nto the same number. As said before pure white is: 255/255/255; pure black is 0;0;0 and red i.e. should give you a number such as (and I make the number up!) 65;65;65. It is not important which exact number but much more that all three numbers are as close as possible in their value. If you hold the cursor over the red pencil and it says something like: 65;87;23 than you can be sure that you have a color cast.

How can that be? Red has a lot of red and little blue or green. Am I misinterpreting something you said?

Here are three diff reds..all have diff R-B-G values, yes?


This is the color of the red near the arrow point ... 


Part B ... I was aware that the white or gray card should be in the same light as the subject. However, this is where this all falls apart for an outdoor photographer. Having a white or gray card in the same light as a bird or moose is not possible. So we process according to what we THINK it should be. That gets confounded by natural light colors and variations in plants and animals. It's a crap shoot. (I am making too much of this obviously because we all see nice pictures here from a lot of people.)

And what of the color cast is a real part of the scene? Then we should not mess with it. That's why we sometimes like the "magic hours" ... specifically for the warm color cast.

I'll stop now. Methinks I am trying to make this too complicated.

Cheers!

Clive
PS: You leaving town for the Olympics or going to to Whistler to watch?

Clive- apologies from me. One shouldn't do two things at the same time...I made a mistake: red should obviously be 255 in the red channel and the others should be 0. As this is very rarely the case I would try this tutorial:
http://www.dynaxdigital.com/digital-darkroom/add-a-tip-for-photoshop-please!/msg29374/#msg29374
I have just done it with your image and it works very well at least according to my colour callibrated monitor.
In a nutshell: there is no denying that yes there are situations where eliminating colour casts are tricky in post-processing and that's why you should use a custom wb to begin with. In yor example with the landscape: you could take a custom wb by holding a white sheet of paper in the general direction ofyour landscape and measure the wb from there.
As a photographer wb and colour casts are indeed issues of great importance but we can only do a certain amount to avoid the problem. It is not a scientifical approach but when using the correct wb to begin with and follow the correct steps in post-processing we can minimise the colour cast problem. There are for sure instances where we will run into problems- your pencils are a good example. But here again a custom wb would have helped. As Chappo says: colour is to some extent subjective- but only to some... when it comes to out of house printing eliminating colour cast does become an issue.

Sorry for the confusion above... my mind was somewhere else...
Stef.

Clive- I wanted to wuickly come back to the above crap that I have written in a moment of confusion...
What I actually really wanted to say is: when you click something in your picture that you know is pretty much neutral grey THAN the three values should be identical. The best method is really the threshold method described above- works in most cases.
Stef.