Studio Lighting - Green Screen

Today we had a go at using green screen. Green screen is a technique used often in film, tv and photography for special effects purposes. It is used to separate the subject from the background and give a clear-cut outline, they are then easy to ‘cut’ around and place wherever necessary. In photography such as advertising this can be useful to scale objects, place them on a white background, or to photograph a background at a later date.
In film it is used where actors have to react and act alongside CGI characters, or in CGI scenes that would be impossible to film in real life, as they don’t actually exist.
In tv it is used for news and weather reports for example, to superimpose news stories and weather graphics behind the broadcaster.

Green Screen being used on set of the 2012 film release The Avengers. 

Weatherman stood in front of green screen with superimposed weather graphic. 

In the studio we used an improvised green screen using green fabric hung on a backdrop stand approx. 6 feet behind the subject. We then took turns to stand in front of the screen and have our photograph taken under a simple lighting set up; in Photoshop we could then apply whatever background we wanted.

It is important to note that the subject MUST NOT contain the background colour (in our case, green). If it does, you must change your screen colour to one that is not intended to be seen in your image, or use a different colour object; the typical colours for this technique are blue and green.

Here are some I made using backgrounds from Google images:

We did a very simple example of this technique. To get the results shown, follow these simple steps:

Open the image in Photoshop, click on ‘select’ from top menu bar, then ‘colour range’. 

A box will pop up with three pipette style icons. Use the first pipette to pick the colour you want to select, in this case the green background.

If the background is not evenly lit you will then have to choose the pipette with a + symbol next to it, click the rest of the areas of the background until it is all selected in the mask window.

Click ok and Photoshop will select the background, invert the selection, and then go to

'select' > ‘refine edge’ to tweak the selection parameters to your liking.

Then you can create your selection as a new layer and place it wherever you want.

To get the most realistic results from this technique, you should make sure your background and subject are lit similarly. If the subject is too bright and the background too dark or vice-versa, the image as a whole won’t look correct even if both images are ok on their own. If you are including full length shots, the horizon line needs to be the same in both images or it will look odd and be obvious that the image is not real.

When making selections, if you are using a real green screen that is evenly lit, you can select your subject with just one click down to the tiniest hair and avoid having issues with soft edges/green being left over.

Here is an excellent example of a use of green screen by photographer Nathan Walton: 

http://vimeo.com/68839278 

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