Chroma key experiences, workflow,tips, etc

virgilr

@vicharris Thanks! Well, I put in a back plate that would be fitting the type of shot and focal length/aperture that I was shooting at.

Yep, I threw a bit of grain in to just help "sell" the shot- not to cover any keying garbage! I can post just the keyed footage over a solid colored background, but that's just boring... ;) It's a very clean key!

vicharris

It's just that easy, eh? :)

Mark_the_Harp

Hi guys - have you come across this resource? Not so much for GH2 as it's already-shot footage - but for experimenting with keying / tracking / matchmoving (there are two pages of different ones - see the link at the bottom of the first page for more: http://www.hollywoodcamerawork.us/greenscreenplates.html

They're all free.

And back to the actual topic, which is GH2 for Chroma-Key, while I'm not totally into Keying I've found this discussion really helpful as I want to put together a music performance keyed into a miniature Christmas scene - for fun really and also to get my head around After Effects a bit more. Keylight really seems to rock - given I've never had that much luck keying in Sony Vegas.

virgilr

@vicharris- yeah, it's just that easy... ;-) I'd say I spent ~3 hours total, from keying to grading. No tricks on the background plate. Most of the time is keying!

@Mark_the_Harp - I'm glad the thread is useful to someone! Good luck on your project, and yep, I've seen the hollywoodcamerawork plates, footage, etc. My friend bought their director series DVD's- those guys are awesome, I love their commitment to the art and craft of film making, and sharing it!

One thing I'm learning with keying- it'll never, ever be perfect. There is always some compromise. THE MOST IMPORTANT THING is lighting your green screen properly! This was simple- I just stuck a piece of green poster board bought at the dollar store to the wall and set up the shot. But even then, I still had some shadow on the screen because I didn't have enough light on the screen vs my talent lighting. I also had spill since I didn't have a large enough green backdrop to put the talent far enough away from the screen to avoid spill.

Keylight takes some working with, that's for sure- it's not a one-click solution. I'm sure there are some other fantastic keying tools out there. both for Ae and in other packages. I just think it's fantastic that it's part of the Ae package! It does do a great job, but take your time and don't get too frustrated. I did a whole lot of resetting the plugin when starting out (still do!) because there is very much a rabbit hole effect when tweaking keys- you think you're on the right path, you have a ton of tools and options to fix problems, but whenever you have to start making extreme adjustments it's best to take a close look at the footage for problems or start over and think your way through.

Thanks to both you guys for your awesome comments!

virgilr

Here's a great series of tutorials on getting started with keylight from creative cow- not every detail is covered, but it gives you a sense of how keylight works, and all the f%^&*#'ing problems that keying poses and how to try and deal with them!

http://library.creativecow.net/search.php?q=Multi-layer+Keying+in+After+Effects

Check out the Multi-layer Keying in After Effects series by Andrew Davis.

under1979

Hi there.

I was supposed to shoot some chroma shots for a shortfilm by end of January with BMCC. It doesn't seem possible due to the BMCC delays and bla bla bla...

Now, i'm considering to get a GH3 for this task. Has anybody experienced chroma tests with GH3. I can do it with my current hacked GH2 but i NEED this extra DR from GH3.... Another option would D800 but, honestly i rather stick with my panny M4/3 lenses... Anyone?

virgilr

@under1979 - Unfortunately not me! Not sure if extra DR would help in chroma keying- usually the shots are done in very controlled lighting conditions where maybe 4-6 stops of dynamic range is captured. Obviously it would be ideal to shoot with the BMCC - I'd love to key some raw footage at 4:4:4!

I know that there would be other shots than chroma key shots on your project and you may require the extended DR of the GH3, as well as matching footage, etc so I can see why your asking.

Mark_the_Harp

I was going to key some harp shots but just remembered why I've had problems in the past - the vibrating strings have always caused me trouble in trying to key them. I think it's because you see through them (nothing behind, unlike most other string instruments) and the strings blur as they vibrate and that blur changes, moment to moment, so the video levels aren't consistent. Maybe I'll try shooting at a high shutter speed in very good light, and get clean images of the strings to make it easier to remove the background then somehow add shutter blur back to the keyed image of the harp after the background has been removed (if that makes sense) to have the strings blurred again.

Or perhaps I'll shoot against a dark background and experiment with what is the best way to overlay the harp image.

fredfred27

That is a tough one! My guess is that the speed of vibration would be too fast to stop the blur. Say you pluck A 440. The sting would complete a full cycle in 1/400s. Even with a shutter speed of 1/400s, the string would still completely be blurred. Each frame would capture an entire cycle. Good luck!

Mark_the_Harp

Yes - and I had a go at shooting against black and essentially doing a luma key. That seems to work much better. Still going to be tricky as obviously the lighting needs to match the scene to work convincingly, and also ensuring that none of the levels of the "wanted" image are anything like the background black. So will keep experimenting but luma keying does give me a very crisp edge to play with.

virgilr

@Mark_the_Harp - that was a brilliant idea to shoot against black! I would try and two-point light your subject, keeping a tonal balance that matches your backplate in terms of light source/shadows, yet avoid any exposure in your subject that is 1/2 stop away from your backplate. Then you can post the keyed footage to get a better match to your backplate in terms of intensity, color balance, etc. I think you'll wind up in a mess if you try to light the actual footage to match your plate without some post to get it closer. Just my $.02

Mark_the_Harp

Exactly - so light / expose the shot for keying so everything is slightly above the background black (and match the lighting / direction so it works when inserted) so i can make the black bg transparent, and then adjust that footage down (or whatever) so it matches in levels etc with the "backplate" (which I assume means the eventual background in the final scene?) - all makes sense. I'll give it a go! The background in this case of course, being on real life a miniature model. Could be fun!

Brokenbarrelpro

@virgilr - I've personally had very good results from chroma keying with the GH2 and a green screen (so much better than the old HDV chromakeying!!). My latest is here:

This was using Driftwood's VY Canis Majoris 'Green Screen matrix setting' at 720P 50fps, Keyed in After Effects using Primatte Keyer, Neat Video denoise plugin, colour corrected, then adjustment layers with unsharp masks and sharpen effects. The denoise plugin really cleans up the alpha channel; I will not chromakey without it, and you can always bring the image detail back with the sharpen +unsharpe marks.

Earlier work (my first GH2 chroma key) that didn't look so good:

This video below was also using Driftwood's VY Canis Majoris 'Green Screen matrix setting' at 720P 50fps, but not as good an outcome as the latest video:

Vitaliy_Kiselev

Howdy, Stranger!

Categories

Tags in Topic

Top Posters