Devin Johnston Posted March 3, 2011 Share Posted March 3, 2011 I'd like to talk to anyone who's had experience working with green screens, I potentially have an in house project coming up that might require me taking a person and putting them onto a digital set. I know how this works in theory but I've never actually done anything as technically sophisticated as this before so I'd like to know what I'm getting my self into. I don't know yet if there will be any motion tracking involved, if there is I have Syntheyes but to be honest I'm not an expert and the few tests I've done result in average results. Obviously keeping the camera still would be much less work but it would be much cooler if the camera was in motion. Please let me know if you have any advice. Link to comment Share on other sites More sharing options...
kmanus Posted March 4, 2011 Share Posted March 4, 2011 -make sure you have the green screen lit equally, this is difficult at the point where the "green wall" meets the "green floor." -make sure the subject isn't so close to the green backdrop that the green starts to reflect back on them (in areas like the shoulders/top of head/ legs/etc....) -make sure the subject isn't wearing green, if this is unavoidable, use a blue screen... I've never done any green screen for CG or virtual sets, but these are some fairly common procedures for working with green screens from a video production standpoint... Link to comment Share on other sites More sharing options...
Fooch Posted March 4, 2011 Share Posted March 4, 2011 If its just architectural background ppl, then do a series of talking people in short frames. Best to get them to keep their feet still because you might have to roto shadows out near the feet which is a nightmare when you have say 50 ppl. If its your first time, dont do fancy tracking bits. Just focus on getting good keyed people in and doing post movement. Thats just adding another level of complexity after keying + roto. To get good keys, you cannot avoid a little roto work. Keylight is great but its not a 1 stop solution. What kevin said is right. Make sure you have enough lights to make the back wall flat.. it will be a warm set, warning. If its a long 10 hr shoot with heaps of ppl, make sure you adjust your camera + lights throughout the day.. or best keep it enclosed so external light wouldnt effect it that much. Do a manual white balance. Plus if the subject is near the wall (keep them 1 meter away at least) you might cast shadows on the back. Do a trials with the same lighting so you can try a quick key. If you are roto-ing parts, roto in segments. Dont draw outlines of the entire "ppl" but divide it to parts of the body. Roto in btwn movements. I normally go incremental say 50 Frames first .. blocking it down then detailing the in between bits. MOVEMENT After you get comfortable with this then add the extra SIMPLE camera pans. Put the camera on a tripod or a rig that allows 1 axis pans. Dont go too crazy with freehanding it first. Put crosses and markers on the green background.You would have to roto them out but thats simple. When you are comfortable with that, freehand it with a good camera rig. Keep the movement smooth. Herky jerky cameras can be a nightmare to match when software fails. -make sure you have the green screen lit equally, this is difficult at the point where the "green wall" meets the "green floor." -make sure the subject isn't so close to the green backdrop that the green starts to reflect back on them (in areas like the shoulders/top of head/ legs/etc....) -make sure the subject isn't wearing green, if this is unavoidable, use a blue screen... I've never done any green screen for CG or virtual sets, but these are some fairly common procedures for working with green screens from a video production standpoint... Link to comment Share on other sites More sharing options...
Devin Johnston Posted March 4, 2011 Author Share Posted March 4, 2011 We're going to use a company that specializes in green screen shooting, several of these issues should be taken care of hopefully by the company. Are there any tutorials for doing roto work in say After Effects? Link to comment Share on other sites More sharing options...
Craig Ramsay Posted March 4, 2011 Share Posted March 4, 2011 Are there any tutorials for doing roto work in say After Effects? There's some on digitaltutors.com but you'll need to pay a subscription fee to access them. Link to comment Share on other sites More sharing options...
Crazy Homeless Guy Posted March 4, 2011 Share Posted March 4, 2011 If its just architectural background ppl, then do a series of talking people in short frames. Best to get them to keep their feet still because you might have to roto shadows out near the feet which is a nightmare when you have say 50 ppl. If its your first time, dont do fancy tracking bits. Just focus on getting good keyed people in and doing post movement. Thats just adding another level of complexity after keying + roto. To get good keys, you cannot avoid a little roto work. Keylight is great but its not a 1 stop solution. What kevin said is right. Make sure you have enough lights to make the back wall flat.. it will be a warm set, warning. If its a long 10 hr shoot with heaps of ppl, make sure you adjust your camera + lights throughout the day.. or best keep it enclosed so external light wouldnt effect it that much. Do a manual white balance. Plus if the subject is near the wall (keep them 1 meter away at least) you might cast shadows on the back. Do a trials with the same lighting so you can try a quick key. If you are roto-ing parts, roto in segments. Dont draw outlines of the entire "ppl" but divide it to parts of the body. Roto in btwn movements. I normally go incremental say 50 Frames first .. blocking it down then detailing the in between bits. MOVEMENT After you get comfortable with this then add the extra SIMPLE camera pans. Put the camera on a tripod or a rig that allows 1 axis pans. Dont go too crazy with freehanding it first. Put crosses and markers on the green background.You would have to roto them out but thats simple. When you are comfortable with that, freehand it with a good camera rig. Keep the movement smooth. Herky jerky cameras can be a nightmare to match when software fails. Solid advice as always. Do you mind if I ask what you background is as far as education and training/experience? You give a very specific description in the difficulties and solution to various parts of the question. I am just curious if it is self taught, or did you find yourself in this field via another of study? Link to comment Share on other sites More sharing options...
Fooch Posted March 4, 2011 Share Posted March 4, 2011 We're going to use a company that specializes in green screen shooting, several of these issues should be taken care of hopefully by the company. Are there any tutorials for doing roto work in say After Effects? Some parts are not absolutely correct but give video copilot's basic training a run. http://www.videocopilot.net/basic/tutorials/04.Keying/ Or if you are doing keylight, use this as a base http://www.thefoundry.co.uk/products/keylight/training/tutorials/ Its for nuke but the concept and background is pretty much the same. With roto work, mmm.. you would make basic shapes.. essentially my major mistake when starting was to trace bits. Its all about using bits of shape and following it around. Think of it as a stickman and go by increments of say 100 or 200 Frames , then fill in the movement in btwn. Dont roto each and every single frame. Block it out first. Oh, nearly forgot.. do a garbage matte first which is cropping it first. Use lots of layers etc. For example.. some auto keys might work for say the legs/body but not the hair. So do 2 separate bits and layer it over each other .. (make a rough cut out of the face etc for the bottom) Link to comment Share on other sites More sharing options...
Fooch Posted March 4, 2011 Share Posted March 4, 2011 Solid advice as always. Do you mind if I ask what you background is as far as education and training/experience? You give a very specific description in the difficulties and solution to various parts of the question. I am just curious if it is self taught, or did you find yourself in this field via another of study? Aww shucks. Thanks travis. I did architecture in RMIT, Melbourne. I was always into new media and worked a little as a flash designer during my uni days and got inspired by KDLAB and all the funky 3D bits.. this gave me a start into how motion worked and thank god for internet tutorials..! There was a max limit on how much work can be done within flash then which got me started into AE early on. Plus I was lucky to be in a research team called SIAL (http://www.sial.rmit.edu.au) which was really experimental (really into game engines for architecture then) which made me pick up a lot of video skills within architecture. Became the default person / staff in uni for "if shit needed to be done call ...." so I got to pick up camera skills because events needed filming in the design department, etc... That lasted a few years where I lectured in uni, researched etc.. Then in 2006 I moved to london and joined squint which was an ultimate crash course on how to do really good work. The great thing about squint in london is we get solid film pros + experts in to help us in comp/post production. So my 2 years there really polished up the post and matte painting part of my skill sets. (Heck, when you work on projects as guys who did the CGI in batman / harry potter etc you are bound to get better). Plus the huge amount of new & difficult/interesting projects we got made learning a necessity. Came back to australia in 2009-ish and we opened our aust studio. Education via osmosis and oh the internet. Best investment the studio made was to get a lynda.com account where everyone learned the skillsets. Plus good gnomon tutorials and of course tricky projects which needed it. Link to comment Share on other sites More sharing options...
Devin Johnston Posted March 4, 2011 Author Share Posted March 4, 2011 You've already done everything I dream of at 30, what do you do now? Link to comment Share on other sites More sharing options...
alias_marks Posted March 4, 2011 Share Posted March 4, 2011 Not sure if it's been mentioned, but I'd watch out for reflective jewlery, watches etc. that might pick up some of the green. Link to comment Share on other sites More sharing options...
Jeff Mottle Posted March 5, 2011 Share Posted March 5, 2011 Devin, if you like I can put you in touch with a few viz companies that have green screens they would be willing to rent out and assist with production. I know of 2 or 3 for sure that have green screen studios in house. Link to comment Share on other sites More sharing options...
Fooch Posted March 5, 2011 Share Posted March 5, 2011 Not sure if it's been mentioned, but I'd watch out for reflective jewlery, watches etc. that might pick up some of the green. Oh yes! Plus I know this might sound weird but if you can keep the fg/close up ppl wearing a hat, or have short hair it would save you time. Dark hair is always easier to key. Long flowy white hair always means more work hours to patch. Frilly skirts or anything a little transparent can be a pain. Wouldn't destroy a shot. It justs makes it harder than it should be. Shoot on full HD and make sure it's progressive. The days of Sd footage that's interlace brings shivers to me. Check the compression settings of the output as well. Some cheaper dslrs output bad h264 which can be bad for keying. Edges of subject can have a little compression muck in it. If budget allows it, this is pretty good. Check it out. You can get away with minimal lights to get a good key. http://www.reflecmedia.com/education/products/litering/index.htm You can only use 1 camera for it though which I found out the hard way! (no close up cam with a wide camera) Link to comment Share on other sites More sharing options...
Fooch Posted March 5, 2011 Share Posted March 5, 2011 You've already done everything I dream of at 30, what do you do now? Get better in max I cheat heaps in post. Would love to get more kick arse at rendering. Plus work my butt off to make sure squint aust grows (gasp. Always a struggle and a learning curve) Link to comment Share on other sites More sharing options...
Devin Johnston Posted March 5, 2011 Author Share Posted March 5, 2011 That would be nice Jeff thanks. Link to comment Share on other sites More sharing options...
DorothyHick Posted March 10, 2011 Share Posted March 10, 2011 I am so great for a nice post, thanks. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now