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Blue Screen

#1
Anyone out there knows how to crop out a blue screen? I have taken digital photos with a blue screen background. But when I use photoshopto crop using the magic wand option, I only can select part of the blue, not all. Any other options? Thanks for the help!
 

Rich

Well-Known Member
#2
I'm guessing that your blue screen has slight variations of blue and the magic wand is only picking one them. Try Select>Similar and see if it picks up the rest of it. Keep in mind that if your photograph has a similar blue in I believe it will also then be selected. You'll then have to "unselect it". Hold down either the Alt or Ctl key while using your selection tool to selectively unselect the affected areas of your photo. Note: I don't have PS here at work and I can't remember which key..doh. Am I close guys?

Rich
 

vogonpoet

Well-Known Member
#3
Hi Poohfin and welcome to the forums.

Instead of using the magic wand tool, have you tried the 'colour range' tool? This is found under the SELECT pull down menu.
It gives you the options of specifying a colour and then using a tolerance slider and the preview window, you can fine tune the amount of colour that is used to create the selection.

Also with the magic wand tool, there are options that allow you to set a tolerance also, it is just not as easy to see the selection as with the colour range tool.

You might also consider using a channel as a basis for creating a selection.

With the colour range tool, a little tip is to pre select as close as possible to the subject you are trying to isolate from the blue bg, with a standard lasso, or rectangular marquee selection. This limits the amount of data used when in the colour range tool and can make the results better.easier.

Hopefully, the blue variations are suttle enough that the colour range tool will do the job for you.

What version of PS are you using?

There is in later versions of PS the "Extract" command that might also be a good method for the problem you describe.

Lets us know how things work and if you have further questions

:perfect:
 

{OZ}

Well-Known Member
#5
Hi poohfin,

I think the reason you can't select the whole background with one-click magic wand is because you have different values of blue. The background has to be evenly lit which is a very hard thing to do.

what you might want to try is that you can select the blue background with Select -> Color Range and from the Color Range dialog box select Sampled Colors. by using the eye dropper with the + sign, you can add different values of blue to the selection. after selecting your blue values, you can switch to "quick mask" mode and detail your selection.

There are alot of ways of making selections. You can use the lasso tools or the pen tools or by switching to the quick mask mode could be other options. Whichever works fine for you.

hope this helps

OZ
 

{OZ}

Well-Known Member
#6
wow!! we've all been typing at the same time?? :rofl:

this looks funny tho.. we've all been talking about the same things..
 
#9
Nah that would be me Oz I have only just got through now :rofl:


poohfin even when they use blue screening in movies quite often even after keying the color and adjusting the mat they can still sometimes have color fringe around the object which has to be removed by using a method of different alpha channels for different areas,ie hair becomes on alpha,arm etc,then all alphas are composited together and then run as one alpha removing the fringe altogether,although I dont now if this happens with the bigger studios now :D


Let us know how you get on,this could be quite tricky depending on your image :)


Stu.
 
#11
Naaa that would be ME Stu :p :rofl:

On top of all the great suggestions here, i'd like to add one of the simplest...

USE the Magic Wand tool poohfin... but increase the "Tolerance" of the tool. Start it at 32, and if it doesn't select all of the blue bg, then add 16 to that amount and try again. Repeat this until the tool selects all of the bg.

If/when it selects too much (by including some of the subject), then drop the Tolerance number down by 8. Tweak it from that point to make the tool select just the bg.

And that's probably the simplest thing to do.

PS: BUT... no matter which method you use, try ALL of the ones mentioned here ok?! Learn as many ways as you can to do this type of thing. Some methods will always work more efficiently than others, in specific situations. So more knowledge means more power for you. :perfect:
 

vogonpoet

Well-Known Member
#12
Mark: late again !! :p heh

  • creating selections in PS is half the battle, as in , learning all the methods available, plus inventing your own methods, is one of the secrets of PS. It takes a little time, but is more than worth the effort. A combination of learning the generic selection tools (marquees, lasso, etc) combined with the colour range tool, the pen tool, and ultimately using your channels to isolate and build a basis for a selection or a mask. Hours of fun for everyone ;) [/list:u]

    never tried the 16 thing with the wand Mark!
    :perfect: gonna have to play now!
    enjoy

    ::edit:: cant believe I omitted to mention the 'quick mask' mode! (slaps self), with which you can make a rough selection, then jump over to quick mask mode, where you can use any of the painting tools to refine the selection, due to the fact the selection is now displayed to you as a masked areas on which you can paint in or paint out areas of the mask, as well as blurring, sharpening etc etc etc...then you jump back to regualar mode and your seleciton now reflects the edits you made in quick mask mode! very handy sometimes. info overload!

    ::edit 2:: Mark ! heh

    cheers
 
#14
Hi people,

Thanks so much for the help that you guys provided. I shall try it out on my pictures and will let all of you know how it turns out. Thanks!
 
#15
Hi,

I have tried the methods, and it seems that it is still not able to select all of the blue. But of course, I managed to get most of it...
 

dv8_fx

Retired Administrator
#16
If your talking about the blue that forms a thin halo around the object you want to isolate, it really won't. That halo is the threshhold of where the solid blue starts to blend with colours next to it. This happens most especially if the image was taken or scanned with a lower resolution.

If you really want to clean that out, it's tedious so patience is the key. Or you can use the blend or blur tools.

vee
 

Anamacha

Well-Known Member
#17
Poohfin:


Hello, and welcome:)

I'm trying to do pretty much the samet hing (the bluescreeen background) with the website that I'm putting in a lot of time on, faerydance.

You guys all have given great info :perfect: ... but I can't believe that someone hasn't mentioned the following:

Check the CONTIGUOUS option fot the Magic Wand tool. If it's on, it will only select areas of the same colour that are CONNECTED. If it's off, then it will select ALL areas of that colour (and that tolerance thing that you've selected).

I've had good luck making difficult selections in Quick Mask mode. As someone else menti0ned, this basically allows you to make a selection with any of the painting tools.

One more thing: You might try the selection | Modify | Expand command. It's a little heavy-handed, but it will grow your selection by one pixel in all directions -- and maybe get you what you want.

If this STILL doesn't work for you, why don't you post the graphic for us, and we'll have a go at it?



Anam
 
#18
If a colour is to be selected, then I would always start with a close look at the channels. Most probably these will have different greyscale values.
I would choose my channel, duplicate it and try to select on that one with masks (start with a soft large brush and the more you approach the edge, the smaller your brush should be, but always use a soft-edged one. finally you should go just across the edge with the soft outer edge of the brush).
Then I would apply that selection to the entire image.
I always try to work in greyscale because most colours contain R,G and B. So when you set a sensitivity at, say 10pix, the R,G and B components will each react differently and no-one can get a clear view of what this exactly will do to the image.
 

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