Photo Retouching - - Making selections between two similar colours

gizmo001i · #1 05-28-2008, 04:28 PM

Hiya guys,
I have no real problems with making selections of normal pics, even down to so called difficult selections. But the one thing I just don't seem to be able to find, is information on making a selection when the forground and background colours are similar. ie red and orange. I have found plenty of tutorials about hair and trees etc, but nothing about this. Can someone please let me know the best technique for making such a selection, as at the moment, I am reduced to spending copious amounts of time refining the edges with a normal brush and the appropriate colour. Which can result in a non-perfect selection depending upon how long I have been at it and how much patience I have at the time lol. Any advice will be very welcome.
Many thanks
Ian

mistermonday · #2 05-28-2008, 07:26 PM

Ian, welcome to RP. Have you tried Select > Color Range? Reduce the fuzzy slide to 0.
Regards, Murray

gizmo001i · #3 05-28-2008, 07:39 PM

Hiya Murray,
Thanks for the welcome. Yes I have, but I find that if there are any light spots (or dark) due to the lighting, I can then often get a cross over with the selection. An example, is some glamour pics I took of my wife who has fair skin. Regretably, I used a white background which didn't quite come out white in the photos. So I would like to be able to change the background colour. However, the colour of my wifes skin is so close to that of the background, that when using replace colour or colour range I get alot of bleed over on the selection. So much so that I need to very carefully and painfully select everything by hand.

pixelzombie · #4 05-28-2008, 07:43 PM

Quote:

Originally Posted by gizmo001i

So much so that I need to very carefully and painfully select everything by hand.

sometimes your only route is a lot of manual work...

Joeven · #5 05-28-2008, 08:36 PM

Hey Ian. Have you tried copying the layer and changing the blend mode to Difference? Sometimes you can get enough separation between the colours to get a good selection. Throw the layer out after you've made your selection.

Joe

lurch · #6 05-28-2008, 09:05 PM

Depending on what color your non-white background ends up, you might find that the a or b channel in Lab works for you. Skin (even pale skin) should be red. If your background isn't pink or orange, should work . . . should is a loaded word, of course.

crazyfly1 · #7 05-28-2008, 09:23 PM

Ian, I would try looking at your rgb channels. Find the one with greatest contrast between the colors. copy that channel and enhance the difference with levels, and d&b.
Control click to make selection now go back to the layer menue and control j to jump your selection to it's own layer.

mistermonday · #8 05-28-2008, 11:04 PM

Ian, in addition to the methods above, there are a number of other techniques that include other PS tools or advanced blending techniques. Can you post one part of the image that is representative of the two close colors you are trying to separate?
Regards, Murray

DiamondsDr47 · #9 05-28-2008, 11:30 PM

You can use selective methods let’s say pentool+others...without a sample everyone trying to shoot out of darkness in order to help you, help others show at least partial sample and i'm sure you get faster, to the point...
Best regards,
Edgar

edgework · #10 05-29-2008, 08:08 AM

Quote:

Originally Posted by gizmo001i

Hiya Murray,
Thanks for the welcome. Yes I have, but I find that if there are any light spots (or dark) due to the lighting, I can then often get a cross over with the selection. An example, is some glamour pics I took of my wife who has fair skin. Regretably, I used a white background which didn't quite come out white in the photos. So I would like to be able to change the background colour. However, the colour of my wifes skin is so close to that of the background, that when using replace colour or colour range I get alot of bleed over on the selection. So much so that I need to very carefully and painfully select everything by hand.

Sometimes it's possible to find enough contrast in one of your channels to build a decent mask from, but more often, the process of enhancing contrast obliterates the natural edge between regions in the original image. Sometimes, the only useful solution is Quick Mask and careful use of your brush, to keep the edge of your mask reasonably in line with the edge of whatever you're trying to separate. The thing is, your eye is far more efficient at discerning natural edges than any algorithm might be. But, once again, the best solution is also the most boring and time-consuming. Nature of the beast.

roger_ele · #11 05-30-2008, 01:18 AM

As previously mentioned/alluded to. Anything in an adjustment layer/blending mode that increases the difference - play and brainstorm along those lines with what could make the greatest difference and throw it out after making the selection. Lab, flip the a or b. - Pump up saturation, - selective color - curves, etc.... control-click the composite channel when you have it and save as a new alpha channel. Paint out the obvious areas and then along the edges use a brush in overlay blend mode, paint with white on the white side and black on the black side to clean or the edges. I don't mask tons so I might have a step skipped, but when I need to get tricky this is the direction I go in.

Roger

gizmo001i · #12 05-31-2008, 07:06 PM

Thanks for all the advice guys, I haven't had time to try them yet, but I will. One way around it I found was to load the raw image and set the sliders to give as much difference between the colours as possible (which is similar to alot of the advice given here). I then make my mask and any changes needed. Once done, I save the photo and then reload it into windows again as a raw file and reset the sliders to give the correct output. However, i will have to give your ideas a go as mine may be a long winded way of doing it. Once again, many thanks.
Ian

crazyfly1 · #13 05-31-2008, 08:29 PM

When you load your image from raw hold down the shift key and you will turn load image into load object. That way you load it as a smart object and you can just go back into raw and move the sliders without saving, saves you some work and drive space.

gizmo001i · #14 06-01-2008, 12:16 AM

Here you go guys, here's a couple of pics to give you some idea. These are slightly easier than the others as there isn't so much of her body in them, but they will give you some idea as to what I mean.

crazyfly1 · #15 06-01-2008, 01:25 AM

gizmo001i,
Channel masks is the way to go.
This would need to be cleaned up a bit but I timed it and it was 7 minutes.
The other is a little tougher, it would likely need multiple masks for different parts of the image and the you combine them in calculations.
Anyway, I used the blue channel, made a copy of it, equalize, increase contrast with levels, dodge and burn. Once it is black and whit fill in the inside of her with black and then you have your mask.
If there is an easier way that works with almost no contrast between items to be masked I want to know.