View Full Version : greenscreen key problem

04 April 2010, 08:28 AM
Hi, I'm having a really tough time with my green screen keying. I'm using primatte and key correct and have followed the tutorials on the red giant page. However, when I ram preview the footage after keying / correcting it, the actors are very digital looking, like distortion or snow , especially in the shadow areas. I have searched tutorials and played with the settings until I'm exhausted. Anybody ever have this problem and correct it? Thank you, Kaz

04 April 2010, 06:57 AM

One of the most important factors in determining how good your key looks is the footage you start with. what was the source footage captured with? has it been transcoded prior to keying? what resolution are you working/delivering in?

Also, you may like to check out Mark Christansen's "Studio Techniques" book which has editions available for CS3 and 4, as he has some pretty foolproof keying methodologies using multiple passes of Keylight.


04 April 2010, 07:56 AM
Hi, and thanks,

I captured it with a canon xl2. The lighting wasn't great, but not terrible either. I'm not sure what transcoding is... but please elaborate =D And what resolution do you recommend? I capture the footage with premiere pro, then import directly into after effects and key it. I'll definitely check out that book asap.

05 May 2010, 05:08 PM
You want HD footage with progressive frames if possible - It sounds as if you are capturing DV1? If so, there is half of your problem. In order to key footage you need pristine footage without artifacts, crazy shadows or blown out lighting. If your source footage is heavily artifacted (Noise, grain etc) then that might be part of the issue. Without some frame of reference like a screen shot of the footage then the advice I give you is just guessing on my part.

If the footage is interlaced - de-interlace it before keying it, but honestly you'll never pull a perfect key the first pass. You have to do several passes for it to look good. For artifacts and noise there are several filters you can use - mostly it's trial and error depending on the source footage.

Post a screenshot of the footage you're working with and perhaps one of us can help you out.

05 May 2010, 08:47 PM
Hey Suz, and thank you. I learned that my lighting is just terrible and has way too much grain in it. I'm going to get a light today to see if that helps and I'll update you with my new results. I'm a little fuzzy on the tech details of capturing / importing / and interlace / fist pass etc , but I will do some studying and take your advice on that. talk to you soon, btw i'm from GA and coming home to visit this weekend :)

CGTalk Moderation
05 May 2010, 08:47 PM
This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.