green screen lighting.

[Roy1]

Has anybody used a green screen for chromakeying. If so do you think vertically fixed 4ft fluorescent tubes, one each side of a small green screen would be sufficient to evenly light the screen. Maybe a horizontally fixed tube above to light the centre of the screen could be added, Any thoughts welcomed.

[TimStannard]

Hi Roy, flourescent tubes should work well as they are fairly diffuse. Screen the tubes well and move the talent as far away from the screen as you can to prevent light spillage onto the talent as the lights you will use to light the talent will no doubt be a different colour temperature.

[Roy1]

TIM. thanks for your input and your advice will be heeded although it may be difficult to place the talent more than three feet in front of the screen in a small room with the camera another three feet in front of the talent. However I'll give it a try. Maybe it would be better to get a bigger green screen and work outdoors on a rare sunny day with no lights, perhaps a reflector might be necessary. I can see a possible problem with wind noise on the mic.

[Dave Watterson]

Sound may turn out to be more of a problem than light ...

Tube lights make a noise that is easily picked up by mics. They often also create electrical interference which may be picked up by the sound recording system.

Unless you are shooting with the intention of showing on a cinema-sized screen, tiny imperfections in green screen lighting should not matter. Most chroma systems allow you to adjust how wide a range of greens they will register. I have seen some dodgy-looking setups produce perfectly workable results. By the time you have your background dropped in any minor issues tend to be masked.

It is more important to be careful lighting the performer/s. The big risk is green light reflecting from the green-screen onto them which may show up on the fringes of hair and clothes. Try to get a light above and behind them just enough to overpower any green.

For both sound and vision: suck it and see! Try out your options using stand-ins if necessary. You may be pleasantly surprised to find it is all easier than you thought.

[Ian Woodward]

Dave Watterson: “Try to get a light above and behind them just enough to overpower any green.”

Of all the advice that others may offer, Dave’s single sentence above is THE key to successful green-screen filming.

I’ve also done much green-screen filming outdoors using only natural daylight for the screen and two circular silver reflectors for the subject and the end result has almost always been as good as anything “fancy” and “clever” done in a studio with expensive lighting.

[Roy1]

DAVE. What you say is very interesting and actually has highlighted a fact that has puzzled me for quite a time. I am aware that Fluorescent tubes make a noise as I hve four 8ft tubes in one of my rooms and | can hear them. I don't know why I never thought of that when I suggested using tubes. However I had and am still toying with the idea of using softbox units with four lamps per box. What I don't understand is that I (rightly or wrongly) that the lamps in the soft box, like energy bulbs, are fluorescent bulbs. If they are, they must work on a different system than the tubes as I can hear no noise coming from the bulbs. Perhaps you or someone else can enlighten me on the subject. I am using the ultra key in Adobe CS5 premiere pro to do the chromakeying and have made successfull tests using old photo flood bulbs and a vey small green screen using a static ornament as the talent.

[col lamb]

Flourescent lighting such as you would buy from B&Q is very basic and very cheap, its cheap for a reason but I'll not go further. All flourescent lighting requires a starter circuit which can be either basic or electronic the resulting effect is that the light hums at 50Hz. More expensive flourescents have special circuits which causes the lamp to osscilate at a high frequency and hence these are known as HF flourescents. The small compact flourescents that are sold as low energy alternatives are in fact high frequency units and the electronics are built into the lamp, its in the large plastic moulding below the glass envelope. OK techie bit over.

For green screen distance matters, as the advice has already been given you need as much space between the talent and the screen, 3 foot just is not enough.

Light the screen with diffused sources to produce an even spread with no hot spots.

Do make sure that the talent does not have green eyes and all clothing, props, etc seen in the shots are on the opposite side of the colour wheel or you will get bleed.

Editing the green screen video material, this is where the MAC shines Final Cut is way better than Premiere, After Effects is way better than Premiere, Edius is way better than Premiere.

Finally if the talent is static(ish) you can place a multi point garbage matte around them and key the area outside the matte, this will produce far better results

[Roy1]

COL. Thanks for the advice which will be heeded. Also many thanks for the explanation about the lamps. This knowledge has now resulted in my forgetting about using Flourescent tubes and will probally use soft boxes with the appropriate HF bulbs. I also wish to thank you for the information about lithuem batteries, a very timely warning.