| Chromanator Tutorials: Compositing Setting up a greenscreen The easiest way to composite is to use a greenscreen. Chromanator can automatically remove the green from the image, saving you the task of having to manually cut out your subject (perhaps an actor, or a miniature). A couple of clicks and you will have a perfectly keyed subject ready to be placed onto another clip. At least, that's the theory. Unfortunately, the process is often made more complicated due to a poor greenscreen set-up. Chromanator has been designed to work with less-than-perfect footage, so you do not need to worry about getting ideal shots every time. Here are a couple of examples of poor greenscreens, both of which Chromanator can still deal with:  
Note the uneven lighting on the left-hand picture. The bottom left of the greenscreen is shadowed, whilst the top right suffers from a major highlight problem and along the top are a couple of big creases. Chromanator's colour difference key can still remove most of the green without any difficulties, requiring only a simple garbage matte to remove the highlight. The right-hand picture is more problematic. In many compositing packages it would be almost impossible to use the shot. However, Chromanator can key out the green, despite the heavy shadowing. An animated garbage matte deals with the scaffolding and the rest of the image. Of course, the general rule is that good quality footage will make the compositing much easier. If you want to save yourself time and hassle in post-production, it is worth spending a little more time and money setting up your greenscreen properly. There are a few things to bear in mind: - When using miniDV, it is best to use a greenscreen (as opposed to a bluescreen or any other colour), because consumer video cameras tend to store more information for the colour green. This will aid the compositing process and result in a better key.
- Your greenscreen can be made from cloth, paint or paper. Each have their benefits and problems. Cloth is excellent if the greenscreen needs to be moved regularly. Paint is ideal if you have a dedicated, permanent studio space. Paper is a good alternative if you do not have the liberty of painting the studio area, but can prove difficult to move if necessary.
- No matter which media you choose to construct your greenscreen, you must ensure that it is of a uniform colour, is flat and untextured and has a matte finish.
- Check that the greenscreen is not shiny or overly reflective.
- Be careful to avoid creases, as these can cause problems.
- Try to construct it in an area large enough to light the screen and your subject separately. This will enable you to light your subject dramatically, whilst lighting the greenscreen in a flat and uniform manner. It is important to not cast any shadows on the greenscreen itself (unless you deliberately want to, of course).
Once you have set up your studio and filmed your footage, it is time to start compositing things together… |
