Colour Correction For Lighting Balloons
Published : 6th Dec. 2006
I have an upcoming shoot in which I'd like to half-correct (1/2 CTS) HMI helium balloons (Airstar Solarcs and Tubes). Trying to wrap gels around the balloons are unwieldy and time consuming, not to mention we are shooting in potentially windy areas. I can't do the colour correction in camera (SDX-900), as I am mixing with other sources.
Airstar's models try to solve this by combining and dimming tungsten and HMI fixtures within the same balloon. Has anyone tried or tested this out? I have mixed 32's and 55's in Kino Flo units before, but it tends to produce a more colourful image as it
introduces more colours from the spectrum -- certainly not the same light as a single source 4400K unit.
Thanks in advance,
DP - L.A. (on location in Oahu)
You could use the HMI in the balloon, choose the 4300K filter on the camera and gel all your lights on the ground to match.
Director of Photography
Film | HiDef | Video
Gel the 'ground lights with 1/2 CTB.. then... when you add a 1/2 'O' in Print or Telecine they will go back to 'normal' and the balloon will go to the 1/2 straw or 'O you desire'. Think thru your 'end desire' and counter compensate the other lights. When shooting night exteriors I often use 20ks (Tungsten 3200) and add 1/2 or 3/4 or Full CTO to my other 'ground ' lights that are to be warmer. When the 'ground' lights are cooled back to 3200 in Telecine or Print the 20ks go cool for moonlight.
Tungsten and HMI's are already full-spectrum sources so mixing them cannot produce "more colours", just alter the colour temp.
I just used lighting balloons with a mix of HMI and tungsten globes and it worked fine for getting that half-blue look. You can check it with a colour temp meter and if you get close enough with the balloon, ballpark halfway between 3200K and 5500K, you can always gel your ground lights if necessary for a perfect match.
The only problem is controlling the brightness of the balloon when switching off globes while maintaining the colour you want.
I had some scenes where the balloon provided too much fill at night, and I had only one 1200w HMI globe switched on out of three possible, and it was dimmed 50% at the ballast, but by the time I turned on a few 2K tungsten globes in the balloon to get the colour to half-blue, the light was brighter than I needed.
David Mullen, ASC
I used HMIs for years for moonlight in spite of the fact that I hate HMIs for anything. We've been using Rosco Steel Blue 117 with tungsten lamps, I've found that, when properly timed the green cancels the blue making the light appear silver grey. Grey is a difficult tonality to produce with neutral colorimetry with colour coupled films. I've had great success with this. If you choose to use HMIs you can use half orange and half plus green. Unless you have a full moon we commonly don't see colour at night.
Roy H Wagner ASC
Director of Photography
Thank you for sharing 117. I own a tungsten package and have been playing with various grades of CTB to achieve a 'realistic' night look. I appreciate the not 'too' blue look and prefer the grey.
At first glance at 117 I would not guess that it would be good for night scenes but with your recommendation I will use it the next chance I get. The nice thing about 117 is that it looks like there will be very little light loss thru it which is perfect for me since I own a 'smaller' tungsten package.
The last feature I shot 'Durango Kids' (Lions gate) was shot entirely with tungsten. I just made a decision going in that I was going to shoot 'old school' and not use HMIs. So, the big heads were 20ks and Dinos w/ dichroics. I was happy with the look of the film tho the elecs complained that they had to drag around the larger tungsten units and heavy cable instead of plugging in 1200 and 4k pars.
In regard to the balloon, it seems easier to counter compensate the lights that are easy to gel instead of wrapping the balloon (impossible).
Mr. Mullens suggestion of mixing inside the balloon is a great idea.
I usually go with the counter compensation method but with the 117 there is little light loss compared to 1/2 blue and using your method I can actually 'see' the blue compared to the warm light on set.. while shooting!.. and not have to wait to post before seeing the 'cooler/ grayer' light.
class="style15">>>I used HMIs for years for moonlight in spite of the fact that I hate HMIs >>for anything.
Wow I'm not alone in the world !
(Not that I haven't given in..........)
Oh, Discharge lights are fine for B&W
>> I used HMIs for years for moonlight in spite of the fact that I hate HMIs >>for anything.
>>Wow I'm not alone in the world !
HMI's were developed by Osram for efficient cool running replacements of tungsten lamps. There was absolutely no correlation between their colorimetry and the requirements of colour film. I've been trying to find a good, physical optics emission spectrum of HMI's somewhere and compare HMI's emission lines with the colour bandpass characteristics of Kodak modern colour negative and reversal films. The emission spectrum you see in the trades, etc. looks "fudged" to me, they don't really show how narrow the emission lines are. I'll bet there's all sorts of mismatch between what an HMI puts out and what the layers in a colour film are looking for.
The bottom line? One has to fiddle and fiddle with colour timing to get HMI to REALLY look good as opposed to colour timing the nice broadband blackbody radiation we call "tungsten halogen lamps". I suspect the only reason HMI timing isn't considered a really bad news problem in cinematography is that the better labs have a lot of experience with just what has to be done to make HMI colour acceptable. But I myself notice that a lot of movies have kind of a funny colour cast that I've also see in a lot of still photography of HMI's cousins (MSR's) being are used in theatrical and concert environments. I own High End Systems intelligent lights myself and my local crack stage photographer never quite gets her digital Nikon shots (a camera that cost enough that, as she puts it, she had the choice of buying the Nikon - or a new car) of my stage lighting using the High End gear to look real good. She makes awesome photos of my stuff lit with 3200K halogen Source Four's, etc.
>>We've been using Rosco Steel Blue 117 with tungsten lamps, I've >>found that, when properly timed the green cancels the blue making >>the light appear silver grey.
I liked Peter James' trick of half CTO and White Flame Green on HMI's, or half CTB and White Flame Green on tungsten. The result is very silvery.
That works on film, though. Not sure what it does on video. And that's the trick: a lot of these tips are about shooting film and timing things properly, whereas the original poster mentioned he was using a Panasonic SDX900 and had to get the look right in camera.
Director of Photography
Film | HiDef | Video
If I had my way I’d still B&W using Arcs.
I’ve used on film thru release print film to tape, and HD.. It all works very well.
Roy H. Wagner ASC
>> If I had my way I’d still B&W using Arcs.
If I had my way theatres would be using arcs !
(I wonder what the Sony 4K projector wd look like with a carbon arc source)