Linearized plates, how should we be keying?

Hey All-

We’ve got a whole sequence of driving comps. They’ve been linearized before we got them- from S-Log (I believe). How should we be keying? My understanding is that the Master Keyer works best in Log? And keyer 3d works best in video space? I assume we convert to log and key? (Getting some very weird results so far, and just unsure of it being a color space thing or if it’s just something that was shot poorly for green screen (praying for the former)).

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Obviously it would be great to know how to work backwards and invert back into the original log but it is probably only important for your OCD to get it perfect.

Any old convert into log. ACEScc, ACEScct or any linear to log should help you with tasks better suited to Log. Tracking, resize or keying for example.

So long as you can convert back or view a context upstream. Think of it as a technical working colour space. If you are just converting to log to help pull a key no inversion is necessary.


This came up for me the other day…haven’t done any keying in ACEScg, what’s your favorite way to bounce these in and out of Log?

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Input transforms in the CM node. You can even use the “invert” button to go back.


Oh nice, I normally do the custom colour transform, but the input transforms seem like a real timesaver and less of a jigsaw puzzle, thanks Andy!

I have been smashing the IBK keyer recently. Really good for detail. Works better in linear I believe.

Somone posted an advanced keying tutortial. By generating a clean plate and feeding it into the matchbox also, then doing a divide between IBK on the plate and IBK on the clean plate. Hard to explain. I will try and dig it out.


Thanks Richard, I forget about the IBK! I feel like I saw this tutorial a while back as well? He uses an infill blur to make the clean plate, maybe?

The IBK tutorial for nuke explains it pretty well from memory.

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I’ve been playing around with th IBK in Nuke and it is so much easier to get all the time details back than Flame.

@PlaceYourBetts would you be able to share your IBK setup? I never same to get good results from it at all.


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Who votes for a @PlaceYourBetts Logik Live on IBK?


Happy to offer some of my time but I’d feel like a bit of a charlatan.
I have gotten all of my techniques from helpful geniuses like Mihran Stepanyan and Eyal Shirazi


Sometimes a picture can be worth a 1000 words


One thing about IBK is that it really is only as good as your clean plate. I almost always paint up a clean plate from actual plate rather than using keying/blur. Sometimes I’ll even go so far as to do a camera track, 3D stab, paint up a frame and then project that back onto card for the greenscreen to create the cleanplate. Nuke has an IBK helper that automates the keying/infill blur to create a fake clean but I find it causes problems as often as it speeds things up.


@PlaceYourBetts that is some setup you have there! Is that based on Mihrans video?

Obviously there is a matchbox that does the IBK for you but a while ago Erwan Leroy ( was kind enough to show me how it worked. I keep it exposed and use it like this.

Several techniques blended into one here. I think it was @mihran who showed the green channel extraction that uses Photoshop Colour blend. I just thought that was so curious that I was determined to try it out. I wasn’t fond of using it for matte generation but I snuck it into the clean plate generation. Curiously versatile on a range of fluctuating shots because it ditches the shading and just uses colour. I found that I could drag and drop that cleanPlate schematic onto most of my shots and with it would generate an excellent hard key.

As @greg mentions, IBK relies on the quality of your clean plate. Most of the errors that occur come from this. Pixelspread Interpolate oftten adds flicker or dark lumps. The other thing to note is that your matte often comes out quite thin. It generates an excellent green suppressed edge key but often requires some type of fill matte.

I spammed this setup on a blue screen job recently and it was excellent. Got me to 80% very quickly.


@PlaceYourBetts Logik live awaits! Would love to see a full breakdown of your process in your own words.

I have quite a few blur screen coming up so I will try and use this technique. I will probably ha e questions of that’s ok?

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Don’t forget you can upload setups here or upload setups to the Logik Portal.



We have a portal?

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The Logik Portal. Yes.


Ah right, I’m still stuck on 2019 So can’t benefit from all this :frowning: