A sharply defined subject on a green screen or almost any flat color contrasting background (clear sky) may placed on another background very successfully by using Photoshop’s Refine Edge command for an accurate selection, elimination of spill light and appropriate mask.
1. Open a file that includes the subject. Let’s call it Subject.
2. Open another file that includes the new setting. Let’s call it Setting.
3. Click on the Background in the Setting’s Layers panel and drag it on top of the Layer in the Subject’s Layers panel. (You may now close the Setting file.)
4. The Subject Layers panel shows the subject, marked Background, and the Setting as Layer 1.
5. Click and drag the lock on the far side of the Background layer to the trash in the Layers panel. The Background Layer now reads Layer 0 and the lock no longer appears.
6. In the Layers panel click and drag Layer 0 above Layer 1.
Now the subject is on the top layer with the setting in the layer below it.
7. Use the Quick Selection tool (it is nested with the Magic Wand tool) to select the subject. If the tool takes in more than you wish, hold down the Option key to subtract from the selection. The selection will not be precise in the hair or fur area. That is ok at this point.
8. With the Quick Selection tool still selected and the marching ants appearing, note, in the Options Bar, “Refine Edge…”. Click on it. A menu will appear. In the View Mode section, use the down marker and from the options, choose On Layers (L). Leave the boxes to the immediate right unchecked.
9. In the Edge Detection section click on the Smart Radius box and move Radius out to 4 for starters. (This varies greatly with subject.) Click on the box to the left of Edge Detection and then click on an edge in the image where Subject abuts Setting. With the cursor half on the subject and half on the setting outline the subject. It will follow the actual contours of the subject – frizzy hair and all.
10. In the Output section click on Decontaminate Colors to remove any subject color fringing and in Output To: choose New Layer with Layer Mask.
11.Option: Experiment with the effects in Adjust Edge before clicking OK. At times, depending on the subject, those adjustments improve the end result.