Well after a bit of a break I’m back with what might seem like a bit of a tedious subject of paint for green screen backgrounds, more over, the difference between DIY paint and professional video paint.
This is something which has been bugging me for a while, why is the “professional” paint more expensive and meant to be better than just normal DIY paint you can get from your local hardware store, after all it still just green paint, isn’t it?
Well yes and no. Yes the greenness or purity of the green is important but its not just the colour which you need to get right for good chroma key work, its also the way the paint reflects light back from the surface to the camera. More importantly the evenness of the reflected light which will make a big difference as to how good a key you can pull with the least amount aggressive adjustment in the keying software..
Just like the evenness of the lighting used is important to help reduce hot spotting, if the paint does not reflect the light in the most diffused and even manor you will have almost the same problem as having poor lighting.
In the video I have two panels one painted with a DIY mix and match paint from Dulux and the other with a professional chroma key paint from Rosco. I show with the aid of technical tools like waveform monitors and some extreme tweaking in Adobe After Effects to show what you cant easily see with the naked eye or even tools like the Green Screener app which is one of my favorites for getting the lighting of green screens right.
Although my studio setup is very simple and not very challenging to get a good green screen background, if you have something like a 3 or 4 surface setup like two or three walls and a floor, all painted green like the image from Qcumber Studios below then you’ll need all the help you can get to achieve a well balanced chroma key. The last thing you need is for the paint its self to become a problem because its not reflecting it back in a uniform manner and creates hotspots due to the way does or does not diffuse the light from its surface.
As a bit more back ground info about the panels and paint, i painted three 8′ x’4′ foamex sheets. The Dulux DIY paint needed 3 coats to get a good solid colour and used just about 2 litres. The Rosco professional paint was a bit thinner and need 4 coats to get the same solid colour and used just under 2 litres.
The lights used were my two x 5′ lighting setup I have used in another video http://video-alchemy.com/green-screen-lighting and they were setup to get the best lighting according to the Green Screener app.
Something which is new is that this was filmed with my Panasonic Gh4 in 4k UHD and recorded in 10 bit ProRes 4:2:2 HQ with an Atomos Shugun, this gives a very clean artifact free video image ideal for chroma key work.
The quality of this pairing is really quite amazing and gave me what looked like an equal quality to the Sony A7s which what i was going to use but the small form factor of the GH4 meant that i had less issues with a shallow depth of field that i would of have with the full frame A7s.
Something which is also apparent is that when you get a really good video source even tools like Ultrakey in Adobe Premier can give you some very good results which are almost indistinguishable from the likes of Keylight in After Effects in the end result on Youtube to almost everyone viewing it. Towards the end of the video I’m using Ultrakey to do the chroma key removal with the two colour green background and if you open it up in full screen in 1080p HD on Youtube you can see how clean the edge is even with this less than ideal duo green background.