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keylight, white outline around subject

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Richard Grahamkeylight, white outline around subject
by on Sep 9, 2010 at 12:21:45 pm

Hi all. I have been trying to get to grips with keylight in after effects for one personal project in particular for my dads retirement. Ive learned alot in the past month being a bit of a research junkie. This sites search function alone has been great. Im a quick learner but I am having a few problems getting a key that I am happy with. I am using a Panasonic sd60 which isnt ideal. However it is a big step up from my samsung dv camera.

My main problem is when I first apply the key, ie use the eyedropper to select a green closest to the subject, I get a pretty good key off the bat apart from a strong thin white outline around the subject. I alwasy set my background to black to start off as it does show up flaws like these. Using the matte view option, with minimal tweaking, all looks not too bad. I just cant get rid of this white outline without using screen shrink or such like. Now, maybe thats all I really need to do but it is losing detail. Can anyone think of a reason for this? Ive watched alot of tutorials and havent come across this as of yet. Using the shrink, it just seems like im masking the problem. Any help would be appreciated.

Richard


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Dave LaRondeRe: keylight, white outline around subject
by on Sep 9, 2010 at 4:19:30 pm

[Richard Graham] "...it is losing detail. Can anyone think of a reason for this?"

Sorry to say, it's a shortcoming in your camera... actually, it's a shortcoming in ANY HDV camera.

They all have lousy color resolution -- they only record one-fourth as much color information as they do black and white information. If you think of the total TV picture as a B&W image with the color overlaid, there are 1/4 as many color pixels as B&W pixels... to make the total TV picture, these color pixels are 4 times bigger than the B&W pixels.

It's good enough to fool the human eye, but not a computer. When you do a chroma (aka COLOR) key, what's good to have a lot of? Color information! And you just don't have it, so you see annoying blended colors at the edges of the subject.

I'm afraid you'll have to make more use of that screen shrink control in Keylight than you wanted to.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Richard GrahamRe: keylight, white outline around subject
by on Sep 10, 2010 at 8:11:35 am

Hi Dave,

Thanks for the reply. Your name has become familiar to me while I made use of the search engine over the past few weeks. 'Daves' stock answers' have taught me alot.

Yes, I know my camera has to take alot of the blame. But, as this is just a hobby, I can't justify moving up a level. Anyway, I found a similiar thread here where somone mentioned the camera adding some edge enhancement. I had already checked this and it was at 0. Last night though, I checked again and discovered that I could go to minus figures. This helped alot, not 100%, but alot. I know Im never going to get great results with a point and shoot camera but its going to end up on dvd anyway and the samples Ive burned seem ok.

I remember you mentioning on another thread to convert avchd before keying. My untrained eye and skills cant see much difference but Im sure its there. Ive worked hard at getting the best I can out of this camera and feel reasnonably happy. Ive read the keylight manaual more than once but still have a lot to learn. I have also discovered, despite Ultras great review in cs5, it is not a patch on keylight.

One other thing that has bugged me though is when I have imported my clips into premiere, selected 'replace with ae compostion', gone into ae and done the key, when I am happy with it I discover that when I go back to premiere and watch it update, the video isnt quite the same. It looks like there are still a few probs with the key despite looking great in ae. Thats a different question for another day though.

Thanks again for the reply Dave.

Richard


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Dave LaRondeRe: keylight, white outline around subject
by on Sep 10, 2010 at 2:15:33 pm

[Richard Graham] "I remember you mentioning on another thread to convert avchd before keying. "

I can't exactly tell if you're running AE 10 (aka CS5) from your posts. If you're NOT, I do indeed recommend conversion. Even though it doesn't mention avchd by name, the same explanation applies:

Dave's Stock Answer #1:

If the footage you imported into AE is any kind of the following -- footage in an HDV acquisition codec, MPEG1, MPEG2, AVCHD, mp4, mts, m2t, H.261 or H.264 -- you need to convert it to a different codec.

These kinds of footage use temporal, or interframe compression. They have keyframes at regular intervals, containing complete frame information. However, the frames in between do NOT have complete information. Interframe codecs toss out duplicated information.

In order to maintain peak rendering efficiency, AE needs complete information for each and every frame. But because these kinds of footage contain only partial information, AE freaks out, resulting in a wide variety of problems.

I'm a Mac guy, so I like to convert to Quicktime movies in the Animation or PNG codecs; both are lossless. I'll use Apple's Compressor, Adobe Media Encoder or Quicktime Pro to do it.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Richard GrahamRe: keylight, white outline around subject
by on Sep 14, 2010 at 3:54:47 pm

Hi Dave,

Many thanks again for the reply. I am using CS5. What Ive been doing so far is the following:

capture footage with SD60 @ 1920x1080 50i avchd
import into AE for keying
render keyed footage @ dvcpro-hd
import rendered footage into premiere project for editing

I have tried converting to dvcpro-hd before importing into AE but couldnt see much difference to keying process. And the only real reason I have even been converting from avchd in the first place is due to my computers inability to edit avchd at a decent speed.

However, I will again convert to dvcpro-hd as per your advice and give it another shot.

Liek I said, turning down sharpness all the way has helped alot but Im still having trouble around the hair. To be honest I am not using a hair light. However, the subject is a good 8 ft away from the screen.

Last night I done things different and iported the avchd clip into premiere and selected replace with AE compostion. But the results of keylight looked different in AE and prem. For example the alpha channel looked great in AE but had blotches of transparency in premiere. Very strange.

Anyway, thanks again Dave.

Richard


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Dave LaRondeRe: keylight, white outline around subject
by on Sep 14, 2010 at 4:30:59 pm

[Richard Graham] "...turning down sharpness all the way has helped alot but Im still having trouble around the hair. To be honest I am not using a hair light. However, the subject is a good 8 ft away from the screen. "

I'm afraid that due to the nature of the avchd codec, you'll continue to have problems, due to what I wrote earlier. You can't improve the footage; the damage was done at recording time. You can, however, prevent more damage from being done by going to a different codec.

The ONLY way to prevent such a thing is to circumvent recording in-camera. Usually cameras have HD-SDI outputs or HDMI outputs when contain far more color resolution. It does, however, require the use of a pricey box like AJA IO, which just isn't reasonable for a hobbyist to buy.

So you're kind of stuck between a rock and a hard place when keying HDV.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Richard GrahamRe: keylight, white outline around subject
by on Sep 17, 2010 at 10:58:31 am

Thanks again Dave. I get what your saying. I guess I will just have to settle for mediocre keys. Not in my nature but nevermind. I have learned alot though but still swimming in the basics. After Effects is a great program.

Thanks for your suggestions but yes I am a hobbyist so the outlay just isnt worth it. I have always been interested in video editing but have only scratched the surface before.

I did a few more tests last night and this time used a hair light and it made a significant difference. I am still not getting great keys but it is a big step up. Before I was having to lose a lot of hair detail but Im now maintaining most of it. So, I think my current results are good enough for what Im trying to do. Theyre not gonna get much better with this grade of camera anyway.

Anyway, thanks for your help Dave. You are a valuable addition to this site.


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