Changing hair background

[Rui Marto]

Hi. I was asked to put a horse, which was shot with a dark BG, into an arena, which is yellow and red. I've made a mask for the horse and everything is ok but the hair. I'm having trouble blending the dark bits between the hair into the yellow background.
Here is a sample:
http://img10.imageshack.us/img10/2510/manzaras.jpg

As you can see it looks pretty bad. Any ideas on how to solve this?

[Vernon]

Try this tutorial as a starting point, found here on RTP:
http://retouchpro.com/tutorials/?m=show&id=335

[Rui Marto]

"These techniques work only on images with strong contrast against flat coloured or white backgrounds .... (still working on a satisfying "shortcut" for a black background..)"

Dam...

Since the hair is white, I get the exact oposite of what I need. I've tried some "screen" modes and some inverted imagery and I'm finally getting somewhere but it's still far from acceptable.

[mistermonday]

Have you tried the Blend-If sliders. If you are in RGB, the grayscale would probably be your best bet. Or if you take the image into Lab color the b channel. Don't forget to split the triangles for a smooth transition.
Regards, Murray

[Crapaud]

If I understand your first post correctly, Rui, the sample you posted is the masked background.

Working from that, copy the blue channel and use levels adjustment and D&B to make it more B&W. Use the new alpha channel to create a mask. Fine tune the mask with a curve.

I've ignored the rope and concentrated on the hairs.

[John Wheeler]

Lots of good input on approaches. Here is another. Just change blend to lighter color and mask for the areas that you want the effect:

Screen shot 2011-07-15 at 2.55.36 PM.png

Murray's approach with the Blend If sliders does the trick as well by itself or in combination with the Lighter Color Blend.

[kav]

Something to keep in mind is that the extraction is only part of the work. Don't get too hung up on that step alone.

[kav]

Adding onto my previous comment, something about hair is that bits of it will sometimes melt into the background. If you don't have solid strands there they won't read as such even if extracted flawlessly which leave you with the options of redrawing, repairing, or getting rid of the offending strands (feel free to add to this list). I would start by cleaning up the flyaways you don't want to retain. After that do your basic extraction with the high contrast techniques suggested. What you need to make note of is that a lot of color correction, smoothing, and repair work come after this as well as possible lighting adjustment. It won't automatically be perfect no matter what. If you take a look at the other thread which mentions the david hill photo dissection, you'll notice that some of the initial cutouts are rough and blended in with the new background. Some also incorporate redrawn flyaway hairs to add further realism to the effect. This is all common but doing it with realism doesn't offer a very friendly point of departure for everyone.