keying

[Realethan]

This is called “spill”, and it occurs when you subject is too close to your screen, both Ultimatte and Keylight generally deal with this automatically.

But it your case all you may need to do is manually balance your white and black points. No keyer is going to give you perfect results right off the bat, you’ll need to tweak the spill-balance and base-matte settings until something looks good.

I’ve used many choma-key plugins for ae including Ultimatte and Keylight, but i prefer dvmatte by dvgarage (especially if your footage was scanned to DV)

[Chris Smith]

Also consider doing the key in a few layers. Not every key is going to work for your entire image. You may need to isolate parts of the image with rough masks and key them with different values.

And just to make sure, you are garbage masking out most of the image except your subject, yes?

I know it’s simple, but some ppl make the key try to work for the entire image when all you need it for are the very edges of your subject.

It is also not uncommon to do garbage masks on the inside of the subject. If you happen to be having problems say on the front of someone’s shirt, keyframe a quick mask over it to keep it out of the equation.

Chris Smith
https://www.sugarfilmproduction.com

[Chris Smith]

Also for future ref, it sometimes helps when doing green/blue screen to softly back light your subject with slightly warmer light. Also use longer lenses and get your subject a good bit away from the screen itself.

So say instead of shooting your subject standing 5 feet in front of the key and your camera another 5 feet with a wider lens, stretch the whole thing out. Have your subject 15 feet away and your cam another 15 and shoot on a longer lens. This will help twofold: Your subject is likely to get less spill and putting your screen more out of focus smooths any irregularities.

Chris Smith
https://www.sugarfilmproduction.com

[Damian Dunne]

Thanx for the reponse guys. All very useful points!
cheers
D.

[Helgi Johannsson]

I recommend the book Adobe After Effects 6.5 Studio by Mark Christiansen, it has for example very thorough explanation on dealing with difficult keying using Keylight, but one could easily apply the methods to other keyers. Take a look.

[Damian Dunne]

Thanx guys! From all your reponses I have been able to pull a great key!! Though I have one last question on the matter 😛

As I was shooting on 16mm at a failry high ASA it has left me with a large grain size. So when pulling the key it takes out the green but leaves behind a lot of gray and blue grain. I have applied a matte choke but with mediocre results.

I know that in Discreets (sry Autodesks) Smoke, it has a pull down menu in the master key section where you can marque a certain area of the plate to reduce the grain in the key. Does AE have a similar function or plugin. What is the best approach for this problem?

Again…. Thank you in advance!
D.