Comping grey screens

Afternoon all
After seeing a lot of very helpful comping tips recently I thought I’d ask the question about comping on to grey screens. Usually I’d use a couple of blending methods to get the desired effect and then luma key anything that goes over the top, which usually then has a few masks to help clean it up, nothing crazy just keeping it simple as I usually tend to work in longform so I’ll have a list that’s pretty extensive!
Does anyone have any good tips they’d be happy to share? I’ve attached a pic of part of the screen to hopefully give you an idea of where I’m starting, the footage to be comped will be dark cctv footage. The footage is locked but they’ve given me tracking markers for fun!

Roto the person, then use Soft Light or Overlay to restore soft and semi-transparent details. ASSUMING the gray is 50% in rec709/sRGB then the details will come back real nice because both overlay and soft light make 50% gray do nothing and do a variation of screen and multiply for values above and below that.

In practice it’s rarely as automatic as I’m making it sound. (see also: every other “trick” in Flame. haha)


I’ll give this a try and see where I get to.
Roto is not what I wanted to hear but then I don’t think anyone does really!
I think I’ll park these 21 shots for now and crack on with the 120 other shots I need to do!

When it comes to cctv screen comps into grey screen, I have done a few.

I like to grade the screen, using the footage, to keep the light grey when appropriate. Trying not to replace but enhance is also a technique I like to use for sky replacement where possible. Shame about those tracking markers but clean them off using a soft patch.

Then a soft luma key and some roto like @andy_dill mentioned.

Look out for the screen edges and hair getting too dark when using this technique.

1 Like

I like the idea of grading the screen with the footage, I’ll have to have a play with trying to make this work. Definitely won’t be replacing the screen but enhancing, it’ll help with the spill that hits the people in front as well.
Thank you for your response.

I’m not a huge fan of grey screens. Some live and die by them, but, when editorial can’t pull a key and then need you to pull all the keys for their edits so they can slug stuff in and get it approved, you’ll change your mind real quick. I’ve never not been able to fix a spill problem. Or, maybe I’m a terrible compositor.

Plus, the guys hair and sweater is basically grey, so…this time…potatoe potatoe I suppose.


I’d love to say this is the worst shot but it really isn’t :tired_face:

Same. I had a moment where I thought they were great, but then another op said something that summed it up for me: “I can make a green screen gray very easily.”


Still photographers like grey.

They don’t want any of that lovely green spill all over the set

This is why I continue to recommend, for shots like this, green paper on the screen. Very little spill, much better than grey, and you don’t even need a functioning monitor.

I think all screens will give spill. Does a grey spill look any better than a green spill that has been suppressed? Not really.

I think they’re all fiddly. The best technique I’ve found for these types of things is either multiplying, adding, soft light, grading, rotoing, (delete as applicable).

When I was learning, a certain Yorkshire flame op showed me how to key. He plugged in the old keyer, selected all the different keyers under the hood and then used the one that got the best result (for this the old keyer was quite special).

“If it doesn’t work after a couple of minutes Johnny, try something else!” was his pearl along with, “There’s no magic button Johnny!”


In all seriousness, “Try everything until something works” is an underappreciated path for most every flame task, really.


It makes me despair sometimes when someone starts saying “This is the correct way to do it because it was shot on a blah blah” or “Well in Nuke…”

The biggest eye opener for me was learning to paint. Just you, a blank canvas, paint and a brush. There’s no magic button.


Well, right. And experience will give you a better idea of what to try first, and more options in terms of things that can be tried, but it can also lull one (me, often) into a “this should work and it isn’t working but I’m going to keep trying” mindset.

Apropos of the current topic: I have recent experience with comping gray screens and not to blow up anyone’s spot but I’m starting to think we should have stuck with black. Or at least significantly darker gray.


With a greater range of techniques you have a bigger selection from which to choose from. Your reasons for choosing one over the others might be down to speed or your assessment of the shot.

I often try the fastest approach first and I might find some issue that stops me from getting the whole shot done using just that method but I can then choose my next method and work on a shot that has less work required. Sometimes a shot requires me to go through all of my fast tricks leaving me the long slow approach at the end. Hopefully my various other passes makes this chore more bearable.

On a tricky shot this can be called the throwing mud at the wall approach.

Yeah I much prefer the screens off. Unless you are in an extremely low light and you must have some illumination from the screen (keep the screen as dark as your DOP will allow).

Convincing reflections can really help bed your screen comp into the the shot.


Having the option to use the real reflection can be quite handy: off screen-no trackers


I’m so tempted to suggest that you request that your clients use an led wall instead of the grey screens and real sets…

You know, just because…

Clients - they’re undeniably just assholes… all of them… it’s part of their ‘agile’ & ‘disruptive’ training…

Can’t live with ‘em,
Can’t volunteer them for Mars trips.

Joel Osis has a great tutorial on this matters:

1 Like

i had exactly this - but it proved a nightmare in other ways.
The not perfectly square green paper had been stuck onto the phone at an imperceptibly slight angle making it almost impossible to get an accurate 3d track - especially as part of the shot involved the phone being placed into a stand that held it at an angle leaning back. When we re-shot the advert for a new product they thought i was mad when i told them to just shoot it with the phone switched off and no markers. Worked so much easier that way.