chromakey semi-transparent

black flour wrote on 6/14/2007, 2:17 PM
When I use chroma key, my subject becomes semi-transparent. I have experimented with it several times and asked pros for ideas why my subject was always semi-transparent. They suggested lighting tips. I am using two 500W tota lights and a chroma green roll of paper 4'X20'. It seems no matter what settings I have for Fstop or shutter speed, the subject is ALWAYS semi-transparent. I have looked at websites that offer tutorials, and their subject always looks exactly like I would expect.

Any ideas?

I'm using Vegas 7.0

Comments

winrockpost wrote on 6/14/2007, 4:48 PM
green screen is about lighting,, posting some pics will get you some advice
Tim L wrote on 6/14/2007, 7:04 PM
How are you applying the chromakey effect?

A very basic (simplified) workflow would be:

1. Apply the Chromakey effect to your clip.

2. With the Chromakey effect disabled (unchecked) in the Video FX chain, click on the chromakey eyedropper, then click and drag a representative, rectangular sample of your background (greenscreen? bluescreen?) in the preview window.

3. Now re-enable the chromakey in the effects chain, but in the chromakey FX window tick the "Show mask only" option.

4. Now drag the "High Threshold" slider down (to the left) until all of your subject shows as solid white. If it looks grey, it will be transparent.

5. Now drag the "Low Threshold" slider to the right until all of your background in the preview window turns black. But don't let it affect your solid-white subject.

6. Add a slight amount of blur (in the Chromakey window) to smooth the edges of your subject.

7. Finally, untick the "Show mask only" box.

Adding a little bit of Chromablur effect ahead of the Chromakey effect can also help smooth the jaggies, especially for DV video sources. Search the vasst site or other places on the web for more advanced techniques for Chromakey.

If you still have trouble, you might have to improve your lighting. Be particularly careful when shooting to not let the subject get too close to the background -- make sure you don't get shadows on the background. Also, adding some rim-lighting on the subject may help.

Tim L
Rattangle wrote on 6/15/2007, 7:08 PM
Take a look at
http://digitalproducer.digitalmedianet.com/articles/viewarticle.jsp?id=31596