The First TenBefore – Keying

Hi,

First I want to give a shout out to Morgan, the presenter and organizer of this project; without him I may have been humming and hahhing about how difficult this was going to be and how I could not find someone to present. Just shows you, God’s timing is perfect and God provides.

Secondly to Dylan, who did the TenBefore transition and background, he’s going study at varsity only next year and think that he’s gonna teach them a few things

Also, just to point to the Previous two posts regarding this series:

The First Ten Before - Introduction

The First Ten Before – Camera, Screen and Lights

Ok, now the nitty gritty stuff that Compositing Green Screen footage is made of.

Here is a typical shot I started off with. Morgan delivering some information for one of the segments. This is medium shot that I found much easier to light and most certainly to key.

I ended up choosing the Primatte Keyer over KeyLight and Chroma Key mainly because it produced the most desirable result after much trial and error. Primatte also allowed me to resample differently for foreground, background, spill sponge and matte sponge.

Because of the inherent short comings of colour decimation in PAL, or for that matter; NTSC and HDV, I had to figure out how to blur the UV channels. This was because of PAL’s 4:2:0 colour sub sampling algorithm; which may be ok for saving on space, bit rate  or whatever, but ummm, it’s an utter head ache for colour keying. hmmm that is why I would love to try out the RED One . A very useful book that give an all round and easy to understand description of colour decimation along with all things compositing is Steve Wright’s book called Compositing Visual Effects: Essentials for the Aspiring Artist, check it out at Amazon here.

I did try the convert to YUV, blur the UV channels and then return to RGB, but not with much success. Instead I found two useful macros for Shake at highend3d - the FourXXEnhancer and PreprocessDV which can be used together or separately. 

I used a small holdout matte and a garbage matte to help the keyer out a little.

Also, maybe as a cheat, I used another keying macro for Shake from hightend3d called Light Wrap, just to sort out the edges of Morgan and to get the effect of actually being in the room. Ok, you would have re-render if you ever had to change the backing, especially if the colour change was huge.

Here is the final result of the matte I was able to produce. The edges were not perfect, but I was quite happy with the edges around Morgan’s head.

And here is my Shake node structure:

Next I’ll chat about how I composited and edited the final sequence.

Feel free to offer and comments, suggestion and criticisms, we are planning to make another attempt that will hopefully be much better and every bit of help would be greatly appreciated.