Fluorescent bulb options for overhead lighting?

R

ReelFilmGeek

New member
So work is wanting to use overhead fluorescent bulbs along the back wall for a green screen. I recommended Kino 5500k bulbs but they want something cheaper. Does anyone have any input about a certain brand of bulbs as I know a lot of the cheaper 8 dollar bulbs will most likely have a strong green or magenta cast.
 
How many? you might get away with tubes, but low power compact flu's are very patchy - and need diffusing, losing even more light. As decent green screening needs even and bright light, you may well end up with really unkeyable evenness.
 
sk810 said:
Basic filmmaker has some good recommendations.
https://www.youtube.com/watch?v=BpOakYp-gJ4&feature=youtu.be
Click to expand...

We use Phillips 5500K T8's from Home Depot for Suzy's studio lighting. A bit of a green spike, but it's actually pretty digital camera friendly and easy to correct. I think the CRI is 85, but it photographs fairly neutral for daylight balance. I think the 3000K version has a higher CRI, but we were matching her north light window for daylight.

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Basic filmmaker indeed has good comments and also some strange ones too. Connect to a dimmer with an electronic ballast. Some will dim, well, dim a tiny bit before they cut out, while other will get very hot, make some odd smells and occasionally catch fire. I like his approach, but unless you know what you are doing - this could be a real letdown.
 
Alzo sold some spirals they claimed are very high CRI, I think they're still on their site.

I'd just do it "fairly right", bite the bullet, and get a couple dual biax units (chinese kino knockoffs). They're really pretty cheap and can be used for many things.

You don't need perfect CRI for a green screen, if you get a bit of green cast it can actually help.

You can dial in your lighting gels by shooting a gray card with a DSLR, opening the raw image, click the WB eyedropper on the card, and looking at the temp and tint sliders.

I did a huge greenscreen project a few years ago - 20' wide screen, 10' high and 10' out onto the floor. I used a mix of biax and clip-light stuff, even made some cheapo fixtures for the big flos. The oddball mix of colors had zero effect on the keys. I just used some china ball sockets and plywood.

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I found those could be greenish, but then, if it's solely lighting a greenscreen, so what.

One of the oldest bit of home-built gear I have is some housings which take 4' T8 fluorescent tubes. This is useful because practically any type of fluorescent tube ever made is available in 4', T8. This includes various coloured tubes, including green ones. They're more expensive than the white ones, but they will be somewhat more efficient electrically so you may be able to sell them on that as well as the potential for improved keys.

Based on the spectral plots I've seen, there are essentially two types of green-emitting fluorescent tube, one of which is the type Kino-Flo sells. Both are available from other manufacturers. I have used both and the non-Kino type is slightly less saturated, which will make for a less ideal separation between screen and subject, but it's more compatible with a wider range of screen colours.

Using green light to illuminate green screens (or blue on bluescreens) is extremely effective. Turn the lights on, and the screen pops out almost in the same way a fluorescent colour does under UV light. It helps a lot.

Obviously, if your subject is going to be under the same lighting, you need to be careful.

P
 
Someone here ran a bunch of tests with green gels for keying a while back. I remember they found a particular Lee green gel to work well.

Problem with that (and with green tubes) is, you need enough space to get your talent well-away from the screen. I think a lot of people rely on spill from their keys to be part of the screen lighting.

As far as minor fluctuations in color balance, AE now includes Key Correct (or something similar?) that balances the green before the key is pulled. I did some experiments once with putting an instance of hue/saturation before keylight, and playing with the green settings while watching the screen-matte display. You really can improve a key this way, but the Key-Correct type plugins are purpose-made to even out all the green hues.
 
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