Ask Dr. Bob - Replacing Background

Today's question is what's the difference between Goobers and Boogers? Actually the difference is merely superficial. These are just two different words that represent what things. And more specifically what things that come from inside your head.
*cough*

Anyway, another idea for a tutorial came from POTN Member shannyD, she was asking if there were any tutorials made about replacing backgrounds on photographs. She'd seen a YouTube video, but it wasn't clear enough. So here I am with another easy to follow tutorial..

Ok we're going to replace the background on this photograph by Lisa Bee from Creations Photography. She also needed the background removing for a Year Book, but was told by the people she was going to send it to that replacing the background wouldn't work..

The photo is used with her kind permission, thanks Lisa.
Ok so the first step is to grab the Polygon Lasso Tool (using a feather of 2px) and trace around the outside of the girl. You want to be in tight, slightly overlapping as you go round, the 2px feather will take care of the overlap when you've made the selection.

An alternative way if you are comfortable with it, is to use the pen tool and trace round with that.

So now we have the selection made and are happy with it, remember you can use the Shift key with the lasso and you'll add to the selection, and holding Alt (Option for you Mac heads) you can subtract from the selection.
The selection needs to be inverted, so head up to the Select Menu and select Inverse or you can use the keyboard shortcut, Ctrl (Command)+Shift+I.


With the Background selected we need to replace it with a colour, so in the Layers Palette go to the Layer Adjustment button and select Solid Color...

You'll be asked to select a colour, Lisa wanted a Tan colour for the background on this particular image, so I picked something tan like that matched the girls clothing and skin tone.

Once you've clicked ok you'll see in the Layers Palette that there is a new Adjustment Layer, a Solid Color adjusment with a Layer Mask, the Layer Mask will be selected and you can go in with the Brush Tool (see the Selective Colour Tutorial for more on painting in Layer Masks) and tidy up any bits that are still showing or need tweaking.

This is all well and good, but the plain background looks a little bland, what do we photographers do to help spice up backgrounds? thats right we stick a light/strobe facing the background to give it some dynamism..
So, holding down the Ctrl (Command for you guys with a Mac) key and click on the Mask. This produces a selection that we will now use to add that light behind our subject!

Now we have our selection. We're going to go to the Layers Palette again and use another Adjustment Layer. This time we'll use the Gradient Adjustment.

We want a Radial Grad, using White as our middle colour and fading to transparent.

In order to get this, click on the gradient bar and you'll get the options to allow you to set up the gradient the way you want it.

Once you're happy with the way your Gradient looks, hit ok, and you're done!

You can also use the mask to create more creative backgrounds..

I hope this has been of help to those looking for a way to create a new background on portraits. Explore, have fun and happy Shopping..

OK UPDATE
sidx001 over on POTN wanted to know how to put a different background in. So here we go.
First take your custom background and drag it into the portrait and resize manipulate as needed. Then once you have it in place, in the Layers Palette deselect your Light Gradient.

Then drag the background in above the Solid Color Adjustment Layer.

Ctrl (Command) click on the Mask in the Adjusment layer to give you your background selection.

Then simply hit the Mask button in the Layers Palette, and your Done!

You may have to tweak the Mask a little with the brush tool to get the results you need..

Have fun!

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