Selecting and masking hair on a solid background isn't too terribly difficult, but doing it over a non-uniform, complex background can be very hard. This great tutorial will show you how to select and mask a subject's hair and convincingly composite it into another image.
Coming to you from Jesus Ramirez of the Photoshop Training Channel, this tutorial will walk you through the process of selecting and masking hair from complex backgrounds using Photoshop. The problem is often two-fold: first, having a non-uniform background means there are some areas that work well with certain selection techniques and tools and others that work with others, thereby making no one tool the complete solution. The other issue is that there will very often be areas that are simply too close in color and/or luminosity to efficiently and effectively separate them from the background. As such, instead of trying to precisely select every single strand (and very likely driving yourself crazy in the process), it's better to use a combination of selection and compositing or simply painting hair back in to make it realistic again. It's a balancing game of getting as much of the original hair as possible before you hit diminishing returns.
I just use the parametric mask….
Oh, wait. Wrong app.
That's not the be-all, end-all way to mask, but it is a good tool. I've never understood why Photoshop just didn't have parametric operators (filters). Motion graphics compositors like After Effects, Fusion, etc have always had it. In Photoshop you have to make a so-called Smart Layer to have parametric filtration, which is not that smart. Masking tools in programs like LIghtroom and Capture One are a complete joke.
Actually LR has improved their masking in their newest LR Classic update. It's a function called "Color and Luminance Range Masking". It's not perfect, but at least it's a great addition to the previous masking options: https://youtu.be/SFuHYJvBXIQ
I haven't tried it on hair yet though..
Yeah they lifted that right out of Darktable, however there are better controls and masking options in Darktable that I wish Lightroom and Capture One had. Check this out:
https://www.youtube.com/watch?v=SKknBy5lX7I
Good info, but his comment that this is the only way to do this is of course untrue, I'm not sure why he made that particular comment. Although equally as tedious (if possibly not more so) are blending multichannel seps from all available channels, as well as using Lab space sometimes to help in separations. Sometimes you can get a surprising amount of specific data, other times not, so all the different techniques, including those Ramirez outline in his video above, become a tool box of options.
you can try it https://youtu.be/767qISu1C5I