Masking in LAB Color space (Advanced)
If you know how to channel mask and how to create a mask from the R,G or B channels and enhancing it with curves and dodge/burn, perhaps even using calculations to mix channels combined with a blending mode, then you are ready for this one. If not, please read the following tutorials first:
Masking and removing backgrounds in photoshop
Masking with calculations in photoshop
LAB masking
Whenever I start to mask something out, my first trip is ALWAYS to the LAB color space, especially if the the object I want to mask out is colored in any way.
Try it right now. Open an image of a flower, or a colored car or something (GIS one of you don’t have one handy), then change the color space to LAB.
Go to the channels palette and look at the A and B channels. One of them will be brighter, pick that one.
Now do the useual and copy the A or B channel you picked, enhance the black and white point with curves and you’r allmost guaranteed to get a mask that’s close the perfect in one go, maybe a bit of dodge/burn and curves but LAB is amazing for many times giving you a perfect mask in a couple minutes that would have taken much much longer in RGB.
In case you’r wondering why, it’s because LAB couldn’t give a rats ass about luminance and stores only color info in the A and B channels. That’s why the mask is so easy to create. The A/B channels will be consistantly light in the areas of color. In RGB luminance is store in each channel so if something goes from dark red to bright red the brightness of the channel will vary making it hard to create a channel mask from it. But in LAB, as long as theres red at all, the A/B channel will be the same brightness, making it dead easy to make the channel mask.
If you’r “one of those” that are worried about the roundrip to LAB just duplicate your image, create the mask and copy the alpha channel over to your RGB version. If you’r working in 16bit I seriously doubt you’r going to be able to detect any degradation, do a diff blend if you don’t belive me.
