cheap lighting and colour temperature

[el don]

hi all,

i'm about to get some of those halogen exterior lights to build a cheap lighting kit. my main concern is the colour temperature. Is there a way to correct it using gels, and where can i find them? I would like to avoid changing the bulbs, if possible.

[jessh]

do you not want to replace the bulbs simply because of the price?
Replacing the bulbs will probably be the only way to get exactly the right color temperature, but you may find that the ones they come form provide perfectly acceptable results. If you are going to be filming where there is some daylight as well then they should give resonable results with a blue gell on them (and your camera using its daylight filter).

Do some tests and see if the lights you are going to be using provide resonable results without any filters.

~Jess

[tim]

Halogen lamps give very good colour rendition, provided the daylight filter is OUT. This may be operated by a separate control, or by depressing the button inside the movie light socket (a short 1/4" BSW screw, like the tripod screw, will do this).

Many later movie lights used halogen bulbs.

[el don]

thanks

i was planning on doing some tests anyway, but i thought there might be some kinds of special gels to correct the colour temperature. i'll have some daylight through the window, so this should give me an acceptable colour temperature.

[jessh]

thanks

i was planning on doing some tests anyway, but i thought there might be some kinds of special gels to correct the colour temperature. i'll have some daylight through the window, so this should give me an acceptable colour temperature.

If you have daylight through the window just make sure to put a blue color correcting gel on the light and have the daylight filter in your camera engaged.

I would also suggest testing the light without a filter on it and the daylight filter in your camera disengaged. That way you can see if the color temperature of it is close enough to tungsten to provide good results (if you like what it looks like that is all that matters), There probably are some filters that could be used to correct the color temparture to be closer to a tungsten balanced bulb, but I dont believe they are very common and if you don't know the color temperature of the bulbs would probably take some trial and error and you still wouldn't end up exactly right (unless you had a color temperature meter), basically I think it would be more trouble than its worth, and possibly evenmore expensive than just replacing the bulbs in the end (of course I could be wrong)

If the lights do provide good results when shooting tungsten balanced, you should keep in mind that there is a chance that mixing them with actual tungsten balanced lamps might not provide good results due to slightly different color temperatures, although it may work just fine.

[S8 Booster]

Some info on this is available at Kodaks WEB site:
http://www.kodak.com/US/en/motion/support/h2/temp.shtml


Some more interesting info:
http://www.photodo.com/art/Take14.shtml

Also from this site: (Filter recommendations are for "daylight" film)




R

[Phil L]

Hi el don,
you can use this kind of garden halogen to cheap light. Their colour temperature is about 2800 °K, so you have to correct (more) with a 1/4 or a 1/8 of blue to be OK.
If you want to mix exterior light (about 5600 ° K and artificial light, you have to correct the lights with a full blue, or correct the windows with a full orange.
Mind this kind of halogen, really cheap but very hot : gels tend to burn...
Excuse my english...

[bfjames74]

Another thing to remember when color-correcting halogen lights is that gels cut the power of the light you're using them on. If you're just adding an eighth or quarter blue, it's not a huge difference, but if you're going from 28 or 3200K to 5600K, using full blue, you lose at least a stop, maybe more (I'm sure what the exact numbers are), which turns your 500W light into a 250W or less light.

(This isn’t necessarily a problem: I just shot some outdoor night scenes using 200T film with a 250W halogen light covered with full blue about 8 feet away from the subjects and was able to shoot 24fps at f1.4.)

If you’re shooting interiors with these lights and need to use a window in the shot, or have too many windows to just black them out, you could shoot with tungsten-balanced film (like Vision 200T) and gel the windows with full orange, bringing them almost to the same color-temperature as the halogens and allowing you to use the full power of the lights.

If you’re shooting outside and need additional light, you’ll have to gel the halogens and if you’re shooting in full sun, 500W lights with full blue on them won’t do much. On the other hand, if your outdoor scenes are short enough, and it fits the material, you could shoot them immediately after sunrise and immediately before sunset, when the sun itself is much more orange, due to the larger distance the light travels through the atmosphere when the sun is low. Whether you do this or not depends on how exact you want to be with your color balance.

A better plan for cheap outdoor shooting, in my opinion, is using reflectors that catch the sun’s light and provide fill on the opposite side of the subject. These can be the flexible type you can buy from photo shops which can cost a lot or something as simple as a piece of white poster board or cardboard with white paper or foil glued or taped to it.

If you decide to go the gel route, be aware that gels can get pricey if you need enough to gel a window. A normal price for a sheet you would use on a halogen light is around $5US, but if you need to gel a window, you usually have to buy pieces of a 4-foot roll. An average lighting company in the US (locationlighting.com) lists gels at $6US per foot. That means a 1 foot by 4 foot piece.

Gels begin to lose their color-correcting ability as soon as you shine a light through them. This is a fairly slow process, as far as I know, but it’s perceived as significant enough that higher-end productions don’t use the same gels for very long. This means that at the end of a day or a week or a production, there are lots of gels getting thrown away that still do almost as much color-correcting as they are supposed to do. Hanging around a production until it finishes could be a pain, but if you know anyone in the higher-end film business (or are in it yourself) you might be able to get some of these used gels for free.

I think viewers are used to some variance in color temperatures. Plenty of big-time movies let windows look “unnaturally” blue and the average person will definitely buy some color temperature differences if you give them a motivation for it. For instance, if a subject is sitting by a window and the blue-looking outdoor light is illuminating one side of them and your comparatively orange-looking halogen is illuminating the other side, show part of a table lamp on that side to give the viewer a reason for the difference in color.

Didn’t mean to go on quite this long. Hope some of this is helpful to someone. I should add that all of the money and gel-availability info is based on my experiences in the United States. I’d love to hear how this sort of thing varies by region.

- Bruce

[jessh]

If you want a cheap reflector for using outside go to Target or some place and get one of the newer cazr sunshades (the thingy you put in the window to keep the car cool), they have ones that have silver reflective material on one side and can be folded up into a really small package (you twist it and the wire frame supporting the cloth twists causing it to colapse and you put a strap around it) I have seen similar "professional" reflectors sell for insanely high prices. The one I have is black on the non reflective side and would be good for use as a flag if you ever needed to flag off a light source.

I have been really suprised with the extreme color temparatures I have seen in films lately. Some of them use so much blue for night scenes that the scene may as well have been shot in black and white and then tinted blue because there is no other color left. I know it is customary to have nights be a little blue but I personally dont like it when it is that extreme. I wish I could remember what movie I am thinking of....

~Jess

[Brandt]

Does anyone know when working with incandescents and halogens how much they can be electrically dimmed before the color temperature noticably changes?

[mattias]

Does anyone know when working with incandescents and halogens how much they can be electrically dimmed before the color temperature noticably changes?

yes, pretty much not at all. it's all about what you're trying to do though. i've found that a little too much orange often isn't a problem. just add a quarter blue if it becomes too much.

/matt

[Brandt]

Would it be better to manage light levels by using clusters of mixed wattage bulbs? Would a 100w bulb going be redder than a 500w bulb?

Also, is there an easy way to simulate the color quality of an HMI?

[MovieStuff]

it's all about what you're trying to do though. i've found that a little too much orange often isn't a problem. just add a quarter blue if it becomes too much.

Seems redundant to use a dimmer AND a gel to correct the effect of the dimmer. If you're going to use a gel anyway, why not just use neutral density gel and leave the lights at full? That way you get the lower intensity you want AND correct color temperature.

Roger

[MovieStuff]

Would it be better to manage light levels by using clusters of mixed wattage bulbs? Would a 100w bulb going be redder than a 500w bulb?

Technically, yes. However, for Kodachrome, which is a type A film for 3400K lighting, a little bit goes a long way. K40 will see 3200 as warmer and household bulbs are around 2800 degrees. They will appear very warm. A 500 watt household bulb might get up to about 3000 degrees but it is still going to be very warm to K40, which has a red bias anyway, even when using 3400K lighting.

Also, is there an easy way to simulate the color quality of an HMI?

Funny you should ask. I've been experimenting with some JUMBO white LEDs. These things are huge; the base is about the size of a quarter and they are BRIGHT, BRIGHT, BRIGHT. Best of all, they are (according to my ancient Kelvin meter) daylight balanced at just under 6000K. Close enough!

Anyway, these things use doodly power. I can run one on a handful of AA batteries forever. I ran one for over a week solid before getting bored with the experiment. My plan is to mount hundreds of them on a 2x4 foot panel as a very tough and portable daylight balanced fill light source that is light weight, self contained and runs on flashlight batteries. Imagine being able to have daylight balanced fill on demand all day long with no outside power required!

I will post some photos when I get it together.

Roger

[mattias]

Seems redundant to use a dimmer AND a gel to correct the effect of the dimmer.

well, sort of, but there are two reasons. first the blue gel lets you keep working with the dimmer to get the exact light level, which a nd does not. second, you might not have any nd gels. there have been quarter blue gels in every light kit i've ever seen but very often there are no nd's. weird really, but perhaps it's because they are hard to maintain since gels get a slight tint from storage and lamp heat, which is much more noticable in a nd than in a colored gel.

/matt