The Perfect Green Screen Key Effect in Photoshop

There are few if any decent tutorials on how to chroma key a green screen image in Photoshop. In fact, I couldn’t find a single decent one, so I created my own.

One of the problems with many 3D programs I use (specifically KeyShot and Vue), is they don’t render out a transparency channel with the alpha. So the light bulb shown below only has an alpha channel showing the silhouette of the bulb, with nothing in the interior. So, the challenge is to how to render an image which can be post processed in Photoshop so that the interior transparencies are preserved.

This tutorial does a good job of explaining how to take a green screen image with transparencies, like a glass or a light bulb, and create a really nice mask for compositing over all sorts of other images. This is great for creating transparent PNG files which you can use in presentations, or on websites, or in advertising. Hope you enjoy the tute..

Creating a Transparent Green Screen Effect using KeyShot or Vue and Photoshop


Step 1:

First of all, create a glass model and set the background color to smDot_01.png GREEN 0,255,0 RGB. This supposes you have little to no green in your original image. If you have green in your original image, then can use RED (255,0,0) or BLUE (0,0,255) for a background color. Set up your render so the final looks like this, and save as TIFF or EXR with Alpha or some other non destructive format. smDot_02.png Do NOT use JPG!


Step 2:

After you have the image rendered, open it in Photoshop and smDot_01.png double-click on the Background layer to change
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the name so it is editable for transparency.


Step 3:

Choose the Channels tab and smDot_01.png Ctrl-click on the Alpha 1 layer to select the lightBulb. Invert the smDot_02.png selection (Ctrl-Shift-I) under the selection menu and delete. Now you should have only the green bulb.


Step 4:

Change the Mode of the image smDot_01.png from RGB Color to Lab Color (Image > Mode menu) then smDot_02.png duplicate the a layer by drag dropping it onto the new layer icon. You should now have a new layer named “a copy."


Step 5:

Switch back smDot_01.png to RGB mode (Image > Mode menu) and then smDot_02.png ctrl-click on the ‘a copy’ channel layer to select it, and with the Green bulb showing, click the smDot_03.png Layer Mask icon to add a layer mask. Your layer should now show a gray mask.


Step 6:

Add a smDot_01.png background layer. It can be a photo or a solid color, but something which you can use to view the transparent object through.


Step 7:

Now for the magic. First, let’s get rid of the green hue. Click on the RGB channel smDot_01.png (the green light bulb on the left) of Layer 0, and then smDot_02.png open the Hue/Saturation dialog (Ctrl-U or Image>Adjustments>Hue/Saturation menu). Select smDot_03.png ‘Greens’ and then smDot_04.png slide the Saturation slider all the way to -100 and smDot_05.png press OK. All the green is now smDot_06.png removed from the light bulb.


Step 8:

Now, the problem is the object is transparent throughout. To fix this, smDot_01.png click on the Layer Mask for Layer 0 and open the smDot_02.png Levels dialog box (Ctrl-L or Image>Adjustments>Levels menu).
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Check to make sure the Channel is named smDot_03.png Layer 0 Mask then click the smDot_04.png Auto button to auto set the histogram sliders. Then smDot_05.png select the right most slider and drag it to the left, all the while watching your image to find the correct point which looks natural. Press smDot_06.png OK and now you should see smDot_07.png your light bulb at full opacity at the base, but clear in the transparent areas.


Step 9:

Lastly, I’ve smDot_01.png created a new layer (Layer 4), and with the smDot_02.png brush settings shown clicked a couple times in Layer 4 to create a nice bulb glow. If I want, I can hide Layer 3 and export this bulb as a tranparent PNG which will composite nicely with just about any presentation or background image.


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3 Responses to The Perfect Green Screen Key Effect in Photoshop

  1. Steve October 7, 2010 at 11:02 pm #

    Very helpful tutorial.
    Wish your blog had a print button as well as facebook share buttons.

  2. altuit October 7, 2010 at 11:36 pm #

    Yep, it’s due an overhaul. Thanks.

  3. Zander September 10, 2011 at 12:08 pm #

    Thank you for the great tutorial!

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