Working with LAB color space

[dots]

Many thanks. I understand now. Back to the drawing board!

 

[dots]

Dodge or burn presents the same saturation side-effect issue due to RGB, yes? Is there any software which allows dodge an burn capabilities in LAB?

 

[clanthar]

Dodge or burn presents the same saturation side-effect issue due to RGB, yes?

Yes! I preach at my students constantly: The best tools and/or methods are the ones that change one thing at a time. For example Photoshop has these white/grey/black eyedroppers in the Levels and Curves dialog. You can supposedly use them to set a white point or black point. One click with either the white or black eye dropper changes 3 things in an instant -- are you really in control? Did you really intend all three of those changes? Do you even know what three things you changed?

Photoshop and GIMP both provide blending modes which are ideal for dodging and burning. I never use a doge/burn tool but I do dodge and burn a lot.

Blending modes:

Multiply = burn (darken)
Screen = dodge (lighten)
Soft Light = raise contrast
Difference = lower contrast

It's a simple matter to extract the Lightness channel from a Lab image and then work on just that as if it were a B&W photo. When you're finished you can replace the adjusted Lightness channel.

To burn an area in the photo extract the Lightness channel and place it on a layer. Duplicate the layer and set the blending mode to multiply. The entire image will darken. Adjust the layer opacity to the desired effect. Add a layer mask to the dupe layer and paint out the effect where not desired by painting on the mask (use very soft edged brush). A mask can be created from a selection.

To doge use Screen mode. To doge and raise contrast use Screen mode and then repeat process with Soft Light mode.

Flatten the layers when you're finished and replace the Lightness channel with the adjusted Lightness channel and you've altered tone without altering color.

Joe

 

[dots]

Thanks!

 

[unpopular]

Photoline allows you to select which color space an effect is applied. I don't know if it's actually somehow applying curves in that space or it it's simulating the effect, but it does work well. You can apply a curves to the lightness channel on an RGB image by selecting LAB from a drop down menu.

I very much do not recommend using the crude dodge/burn tools, but rather use a curves adjustment layer and mask in areas that should be affected. I kind of feel like the dodge/burn tools are a bad habit.

 

[unpopular]

Also, one thing I often times will do is make an adjustment (typically in RGB mode) that I know is slightly more extreme than what I am after, duplicate it three times and place each copied adjustment layer in three modes: Lightness, Hue and Saturation. This permits me to adjust each quality fo the adjustment separately by manipulating opacity.

 

[Buckster]

Easily the best video tutorial series I've ever seen on LAB: Photoshop CS3 Tutorials | Mastering Lab Color

 

[dots]

Thanks for the link!