[superfrasky]

Hi friends. Im trying to make a perfect selection this image. The image was shoot with chroma background (blue). I need remove background (blue) but I can not remove blue highlights in hair. I have primatte chromakey (digital anarchy) but dont remove spill (blue) in hair. Anyone know a good method?
Thks

[byRo]

I would convert to LAB mode and have a look at the A and B channels.
Duplicate the layer and run levels on one (or both) of the channels marking a black point on the background and a white point on the hair.
You should be able to make a pretty good mask combining these two channels.

Rô

[meok]

Hi
This is how I would approach this: http://byloc.com/hair-extract.jpg

1. Original Image
2. Mask made using calculations. (Multiplied the inverse of an enhanced red channel into an enhanced blue channel.)
3. Result of applying that new alpha channel to the hair, we can clearly see the blue highlights.
4. Mask made with calculations by substracting the blue channnel with the red.
5. Result after using that second alpha channnel to mask a level (or curves) ajustment layer that subdued the blue cast.

Note that you can get much much bettter result if the file has better resolution and less jpeg artifact that the one that was posted. Hope this helps, good luck!

[superfrasky]

Originally Posted by meok

Hi
This is how I would approach this: http://byloc.com/hair-extract.jpg

1. Original Image
2. Mask made using calculations. (Multiplied the inverse of an enhanced red channel into an enhanced blue channel.)
3. Result of applying that new alpha channel to the hair, we can clearly see the blue highlights.
4. Mask made with calculations by substracting the blue channnel with the red.
5. Result after using that second alpha channnel to mask a level (or curves) ajustment layer that subdued the blue cast.

Note that you can get much much bettter result if the file has better resolution and less jpeg artifact that the one that was posted. Hope this helps, good luck!

Great work meok, but I dont understand step 2 and step 4, anyone can explain it more in detail?

[superfrasky]

I need help.... I can not remove blue background and blue hair highlights....HELP, HELP,HELP

[Cameraken]

Hi Superfrasky.

Meok provided a great method which works fine on this picture. However there is perhaps a more useful method here which works on most images.

http://www.russellbrown.com/tips_tech.html

And Larry provided a great explanation here

http://www.retouchpro.com/forums/showthread.php?t=11544

Larry painted out the colour Before the extraction but it can be done after with a layer set to colour and applying the same mask. It can look more natural if you add some colour from the new background.

Hope this helps.

Ken

[superfrasky]

thks cameraken, but meok method I think that is good for this image. the problem is that I dont know how make him (2 and 3 step of method)

[Cameraken]

Hi Superfrasky.

I think Meok must have a few extra steps. I don’t really understand calculations.

OK. I’ll try and learn with you.

Dupe the Red Channel
Dupe the Blue Channel

On the Red Copy Channel adjust levels
0 1.00 172

On the Blue Copy Channel adjust levels
0 1.00 213

Select Image > Calculations

Source 1
Channel Blue Copy

Source 2
Channel Red Copy Invert Checked

Blending Multiply

Click OK

This makes a new Channel, Alpha1
Image > Adjust > Invert
Adjust Levels
30 1.00 192

This gives something very similar to Meoks Second Picture.




Ken

[aztek1020]

are you using photoshop or paintshop pro?

[Swampy]

This was a challenge, but here's what I came up with.

Basically did a H/S to put some more color in the hair first.

Used the red and green channels combined (see the great calculation tutorial above, Thanks, Ken!) to generate a mask

Inverted the mask and deleted the blue background.

Used Photoshop's Color Replacement tool (Under the Heal brush) to replace any remaining blue spill. You can go back into Curves and soften the whole thing to more closely restore the ash blond (original) colors.

This looks best on a dark background.

[byRo]

I read through meok's method and it's pretty much the same as I did here using the LAB channels.

1) Duplicate the layer;
2) Run levels on the A and B channels marking the background as one extreme (black / white) and the hair as the other;
3) Use Image>Calculations to form a new channel by multiplying the modified A and B channels (have to invert one of them);
4) Make a new duplicate of the original image and apply this channel as a mask;
5) Run Levels on the mask until you get the best possible masking of the edge hairs (don't worry about the inner hairs);
6) Paint the mask to show all the hairs away from the edge;
7) The hairs are now separated from the background, problem now is the colours - take a paintbrush set to blending "Colour" and sample from the "good" hair and paint on the "blue" hair. Vary the sample to get a few differente hues;
8) Put in your new background.

Rô

[Cameraken]

Originally Posted by Swampy

(see the great calculation tutorial above, Thanks, Ken!)

Ha Ha. Swampy. That wasn’t a tutorial. That was a complete Guess based on Meok’s method. I have read loads of things about calculations and still don’t understand it.

I understand how to use it. But I don’t understand which channels I should be using or Why and I don’t understand which blending mode to Choose. I guess it will come with practice.

Rô. Your picture looks great.
Using Russell Browns method (as I did in my first post here) some of the stray hairs look very ‘fat/thick’.

I will try your method.

I still think Leuallen’s method of changing the colour of the stray hairs to the colour of the new background Before making the selection makes a lot of sense.


Ken

[bart_hickman]

For step 2, he multiplied the inverse of the red channel and the non-inverse of the blue channel. Both the red channel and blue channel were enhanced prior to multiplication. You could enhance them as needed (curve, channel mixer, etc..) to get good contrast. This can be done interactively using adjustment layers rather than layer arithmetic.

For step 4, he subtracted some percentage from the blue channel and replaced that with an equivalent percentage from the red channel. This works because the hair has roughly equal red and blue channels. Again, I found that the channel mixer was more interactive for this step--go to the blue channel, set blue to 20% and red to 80%.

Very educational.

Bart

[mistermonday]

I simply converted the orig image to LAB and selected the B channel (most contrast) and duplicated it. Then using the Apply Image command, applied the B channel to itself in Overlay Mode. A simple levels adjust to boost the contrast and the mask was pretty well done. Like Ro, I painted away the blue in the edge hair. Regards, Murray

[Kraellin]

if i understand what you want, you want to remove the blue background, but save the blue highlights in the hair? is this right? that's how i read it, so i did this:

craig