Adobe Photoshop Training with Dan Margulis

About a month ago, I posted, trying to jog my memory about a technique Dan showed us in his 3 day class. Some he restored the blue sky in a mountain scene. In the raw version the sky was white, not because it was cloudy, but because it was too bright for the rest of the scene.

I think I recovered the memory of what Dan did:

1. Make a very rough selection that includes the sky and nothing else

white (Hmmm, what if there were snow?)

2. Use selective color->white to add color to the sky.

Great! Now I can make the sky any color I like in this (all to common) situation. But the question is, what color should I make it?

Take a look at:

http://rutt.smugmug.com/gallery/37643

Here are two shots that I retouched that started off with white skies. In both cases, I steepened the A and B curves in LAB to try to bring out the New England autumn colors. (I think this was especially successful in the river shot.) And then I followed the above formula. But the question was, what color to make the sky anyway? I don't think I really know the answer. In the river shot, I found a little blue (actually cyan) in the branches of the tree in the upper left. I figured this was a good color and used it for the sky. But it looks too cyan to me. Is this just a matter of trial and error, or is there some useful fact about this that I don't know?

There is another more technical photoshop mystery. When I make the selective color move, PS 7 gives me lets me specify the new color in CMYK, no matter what color mode the photo is in. But it behaves very differently in CMYK than it doesn in RGB. In CMYK, increasing the cyan makes the sky look blue. In RGB, it makes it look cyan. Why?

___________________________________________________________________________

John

I'd use the blue reflected in the water. Try a gradient rather than a solid blue. Darkest/saturated blue at top and lighter at edge of building. If this wasn't there I'd use sky from other photos taken in similar time of year.

Lee

___________________________________________________________________________

John Ruttenberg writes,

Like most repressed memories, this one isn't historically accurate.

The method I currently advocate for totally blown-out skies is as follows.

1) Convert to LAB.

2) Establish a duplicate layer.

3) Drive the duplicate layer toward blue by pushing the B channel curve in the blue direction.

4) Open Blending Options in the Layers palette. Choose Luminosity>Underlying Layer and move the left slider almost all the way to the right. Break that slider in two by clicking on it with the Option key depressed and spread the two halves slightly.

5) This will limit the blend to blown-out areas and the lightest transitions. It will add a blue feeling. If other light areas away from the sky are getting too blue they can be eliminated at this time with a layer mask before flattening the image.

The advantage of this method is that often the background gets very light where it hits the blown-out sky. The edge between the new sky and the background will be very smooth, since it doesn't darken any part of the background, but it does make it slightly more blue to match.

One would like to be able to do this in Color mode in RGB, but it won't work. As the luminosity of the sky is 100, Color mode can't add color to it because in RGB the lightest possible color is a pure white. But in LAB there is no such constraint. 100L 0a -7b is a blue that's too light to be in the gamut of either RGB or CMYK. But Photoshop has to convert it into *something* when the file goes into RGB, so it picks an agreeable light blue, without darkening anything else.

Dan Margulis

___________________________________________________________________________

Dear Dan,

Is it Luminosity, or Lightness?

Best regards,

ib

___________________________________________________________________________

I think there may be a technical difference but in practice people use the terms interchangeably, Photoshop tends to use "Lightness" in referring to the L channel. That's the term that I should have used in describing the Blending Options dialog.

Dan Margulis