Believable chromakey (or Chroma Key) is now not only reliable but, provided it’s used properly, is also pretty attainable in most situations. With this being the case, plenty of manufacturers have begun to produce chromakey kits, which is pushing the technology forward and the price down. So, with the reality that every studio is now able to have a decent and cheap chromakey set-up, the question is no longer “Can we afford a chroma key set-up?” but rather:
“How much should we pay for it and how should we use it properly?”
There are basically two types of chromakey set-ups available at the moment; traditional green screen and reflective. They both work on the same principle of creating super-imposed keys on just one colour channel, R, G, or B. Green (sometimes blue) is normally chosen as it is a less common wardrobe choice and modern cameras are generally more sensitive to green, meaning a higher level of accuracy can be achieved. Green and blue are also considered the colours least like skin-tone.
The subject then stands in front of a matte background of the selected colour and the signal is altered to replace that colour with an alternative signal – a nice weather map for example!
The signal alteration can be done in post-production through software with various editing packages and plug-in software solutions, but for live productions the foreground and background video must be combined using a hardware keyer.
And there it is – it’s as simple as that! Well, sort of…
Back to the two main types of chromakey set-ups. In a traditional green screen set-up the subject is in front of a bright green background. Set up correctly, this can produce amazing results, provided there is good even lighting on the screen and at least 3 point lighting on the subject. As such it is well-suited to a permanent set-up in a spacious studio. Lastolite’s collapsible backgrounds are great for this. Vivid colours and a wide range of sizes are available, or you can simply paint the background with Chroma paint.
With a reflective chromakey setup, the subject stands in front of a background containing millions of glass micro-beads that reflect light put out from a ring of green (or blue) LEDs mounted around the camera lens. The previously grey screen then becomes green. To the eye, the screen doesn’t appear particularly green; the camera picks up the single frequency light emitted by the LEDs creating a pure green matte background. At close range this can give fantastic results. Predictably, with increased distance the light drop-off means the screen may start looking grey again but, in terms of budget solutions, this method really can’t be beaten.
Backgrounds come in all sizes and, perhaps more importantly, so do the rings – meaning that a ring can fit any lens you care to mount it on and if it doesn’t fit immediately then the supplied adapters will make sure it’s snug. One of the main advantages in this set up is that lighting is only required for the subject. As with a traditional green screen the subject will require the usual key, back and fill lighting, but unlike a traditional set-up the screen itself doesn’t require lighting at all.
With the option to switch between a blue and green light ring, you can easily change the colour used for your chromakey (just in case a guest arrives in the studio wearing a bright green jump suit…). All light rings come with a control box to adjust the level of light emitted, and all that remains is the “tuning” of the keyer into your setup.
For smaller cameras (72mm) the Datavideo CKL-200 kit is good value and produces great results for professional corporate videos or educational projects. It has the added benefit of changing between green and blue at the flick of a switch. However, the keyer only has composite in and out, so isn’t of the highest quality available.
For larger cameras and broadcast standard kit (still at an attainable price) the Reflecmedia kits are not to be sneezed at. With the option of collapsible backgrounds it makes putting up the kit a cinch and taking it down only slightly less so! The light rings come in small (72mm), medium (112mm) and large (147mm) and with the whole gamut of adapters for differing lenses.
The Ultimatte DV keyer supplied with these kits has not only composite in and out, but also DV in and out. Admittedly not at the same time, but with the onboard frame store, it’s possible to import the background required, store it, and then digitally output the keyed video unlocking a whole new level of quality for affordable and reliable chromakey.
With great solutions at low-end prices there’s now no reason to miss out on a chromakey set-up whatever situation you’re in, and for a simplicity on a budget the reflective set-ups are so user friendly it’s pretty hard to go wrong.