Keying Problems/Help
by Justin Toney
on
Mar 18, 2008 at 3:50:29 am
Before I begin, please use this image as a reference...
I am having a terrible time with a key in After Effects.
For this project I am using Primatte Keyer which is doing
somewhat of a good job. I have a few different layers setup
where each focuses on a different issue (from basic key to
key for hair). This was suggested to do because it would
help created a cleaner alpha channel. Next I was told to
take these layers and use Alpha Add so that they would all
come together to form a single alpha channel (I hope I did
this right). Afterwards I brought that composition into a
new composition which included the original footage. The
treated comp was used as an alpha track matte which gave me
unfavorable results (as seen in the picture). What is
happening is that it appears that there are waves going
across the edges of the keyed image. I can see the blue
screen moving around and it doesnt look good at all. I have
tried to choke it a bit but the blue still appears. Does
anyone have any suggestions on how this can be corrected?
Additionally there is an issue with spillage on the comp.
I have tried using many spill killers but mixed results.
However, none seem to remove the blue without totally making
the image useless.
If anyone has any suggestions I would love to hear them. And
if I am not doing the alpha correctly, just slap me a couple
of times and let me know. Thanks a bunch!!!
Re: Keying Problems/Help by Brian Berneker on Mar 18, 2008 at 6:41:17 am
Man, I don't know where to start.... if your using AE CS3, I'd say ditch primatte and use Keylight. Nothing against primatte - I honestly don't know it that well, but Keylight has been the best keyer I've ever seen and it comes standard with AE CS3.
Re: Keying Problems/Help by Andrew Wade on Mar 18, 2008 at 7:15:54 am
the problem your seeing us due to a poorly lit forground. that is some pretty bad spill on the actor there.
I'd reccomend using keylight as well its an excelent keyer. and comes with some good spill suppression. If you are going to use keylight pay attention to the graining that can sometimes occur once you apply the final key. twear the despot controlls to get it looking right,
Re: Keying Problems/Help by Justin Toney on Mar 18, 2008 at 12:34:04 pm
Like I said, it was lit poorly which I had absolutely no control over. I will try your keylight and see what I can come up with. I have absolutely no experience in using that so hopefully I can get something.
Re: Keying Problems/Help by Steve Tarlton on Mar 18, 2008 at 4:55:05 pm
Not having seen your original footage I couldn't say for sure, but I would guess that you wouldn't get the "wavyness" on the edge. You could have the so called "jaggies", but if you turn up the screen softness a little that should help. If you keep tweaking keylight you can probably pull an acceptable key.
Re: Keying Problems/Help by Darby Edelen on Mar 18, 2008 at 6:55:49 pm
I realize we're looking at the effects applied to the original layer and not the layer that has the key applied, but I couldn't help but notice the PrimatteKeyer effect applied after several Change To Color effects and a Hue/Saturation effect. Do you have any of these effects applied on your keyed footage layer? You should pretty much never use any color correction effects before trying to pull a key...
Darby Edelen Designer Left Coast Digital Santa Cruz, CA
Re: Keying Problems/Help by Darby Edelen on Mar 18, 2008 at 9:49:18 pm
[Justin Toney]"What I was told is that I should apply color effects to make the keyed footage more keyable"
I personally think that's a bad suggestion, you're more likely to make the footage less keyable, especially with Hue/Saturation changes. Most keyers work to determine the foreground and background based on a difference in hue and saturation between some defined 'screen color' and the color being tested. If you have a green screen and you try to make the green 'greener' in hue and boost the saturation, you are also making everything else 'greener' and more saturated and therefore more likely to be keyed along with the screen. Although you can limit the range of your hue/saturation adjustment, and this may possibly help your key, it is more thank likely redundant because the keyer is already looking for a very limited range of hue to key... and if you're off at all in your limited hue/saturation adjustment then you could inadvertently make certain areas of the footage more or less keyable.
My analogy would be having trouble finding your keys in the morning. It would be like going outside, attaching your house to a crane, flipping it upside down and going back in to look for them again... Eventually the keys might come tumbling out, but more than likely you'll just make a mess of your house.
There are adjustments you can make that will benefit you though, such as reducing noise/grain.
Darby Edelen Designer Left Coast Digital Santa Cruz, CA
Re: Keying Problems/Help by Justin Toney on Mar 20, 2008 at 3:25:21 am
Its all coming together nicely, but if I choke the comp too much I start losing more good stuff so I guess I will need to find a happy medium between "waves" and surface area. I still have some blue spill that I can't remove though :(
