A View From Behind The Meter
The History Of Making Use Of Color In Movies
There seems to be still confusion about the principles of CRI (Color Rendition Index) and how it might affect the final image of the Cinematographers work. I can truly understand why this confusion would be present today in that it wasn’t until about six years ago that I first heard the concept myself. When I first started out in the early 1960’s all that was important was to get enough illumination so the cameras could record the image. The meters I used at that time told me the light coming from the instruments in foot candles and the lens opening relative to that level of brightness. Beyond that, there was no other requirement expected of me as far as light value that I had to become involved with. I remember clearly walking the set with my Brockway Meter and making sure that 400 foot candles of illumination covered the entire area where the cameras would record the activity for that shows production. The instruments were all incandescent 3200 fixtures, usually Fresnels or large “scoop” lights, with spun glass diffusion to soften the effect of the tungsten filament clear globes. This was all black and white television captured by large image orthicon three lens turret cameras, which were perched upon rolling pedestal bases, and each was linked to the control room by a heavy cable. The television tubes required a certain amount of light and the instruments that produced that light were all hung from the pipe grid on devices called a “panagraphs.” The only consideration was whether the light was hard or soft and in shadow or out of shadow. We certainly had no consideration for CRI.
Once I moved into color photography color temperature became an important aspect of the light, and, of course, what film emulsion or ASA we were using, but again CRI was not a consideration. This was all before HMI’s began to appear on the scene. All the lights used in color photography during this period were tungsten 3200 based lighting fixtures almost exclusively Mole-Richardson with a few Bardwell-Mc Alister or Colortran manufactured instruments thrown into the mix. Everything was based on 3200 Kelvin and even when stepping out into the sunlight we would put CTO filters on the lenses to keep the 3200 color temperature base consistent shot to shot. This was during the seventies and early eighties. It wasn’t until well into the mid-eighties that HMI’s began to really be a part of the motion picture process of light. The innovation of HMI’s began to take over what carbon arcs were accomplishing due mainly because it eliminated the need to have a man on every light when working on exterior set-ups. Once an HMI was set up and operating, the lighting technician could walk away from the instrument and proceed to other lighting tasks allowing for a much more efficient use of the labor force. Arcs required the lighting technician to stay with the light at all times and I spent many a day on a twelve foot ladder hugging my arc and almost lovingly never leaving its side until I heard the “It’s a wrap” call from the Assistant Director.
The Time When HMI Lights Became Hollywood Gold
Once HMI’s came into the picture I realized that I needed a color temperature meter. To this point I had been using only a Spectra Incident meter and a Pentax Spot meter. With the advent of the HMI the element of correct color temperature became almost as important as F-Stop and contrast. I was using, at the time, my Spectra incident meter to establish F-Stop or the lens aperture setting and my Pentax spot meter to gauge contrast within the frame so that nothing was overexposed based on the aperture setting we were working with. Now, however, I also had to make sure the HMI’s were giving me the color temperature that matched the suns overall light at that time of day. It was very obvious that sunlight varied with the cloud cover and time of day but the HMI produced the same light at any time of day, so it was up to me to make that adjustment for the cameramen. The color light meter was an expensive toy at the time but I felt that it was an important element to offer the camera staff that I worked for. HMI’s, by their very nature, seldom had a color temperature that matched any other HMI instrument. If we rented four HMI’s there were four different color temperatures that we had to deal with. In many cases I would build gel packs that worked with each individual light in order to make them all compatible to each other.
I cannot remember at any time during the eighties or nineties, with the introduction of Kino-Flo florescent tubes and mixing them with HMI’s and tungsten instruments, that CRI was ever a consideration. In the first ten years of the 21st century during which we, as lighting technicians, began to see LED lights from the manufacturer Litepanels enter into our inventory. I remember buying some of the first that were put on the market. But even then as they entered during this time period CRI still hadn’t become a strong element in our calculations. I can remember clearly the study opening the can of worms that began to question the quality of light emanating from these original 1×1’s. It was done by SMPTE and was quite illuminating as well as controversial. Here at Birns & Sawyer we conducted our own test and requested LED manufacturer’s to bring in their products and let us test them with a spectral radiometer that Bill Meurer our CEO had been using with his GO Green LED manufacturing concern confirmed to us that the SMPTE tests were accurate and the LED instruments that were available at the time did not render color accurately. We also tested tungsten, HMI and Plasma and found quite a discrepancy between instruments as far as accurate color rendition throughout our lighting inventory. So CRI began to be a factor and most people, whom I questioned about the topic, had no idea what I was talking about. It was an unspoken fact of life at the time.
Color Rendition, in simple terms means, that a lighting instrument, in order to accurately render the proper color to the capture mechanism, must have the color within the photons produced by that instrument. If the color is not in the spectral radiance produced by the source it cannot reflect that color accurately to the camera. In the early LED’s it was common for the CRI to be below 80 and I have measured many since, including just this last Tuesday, which recorded 71 to 76 CRI. All of those, which I recorded with my new meters, have been in rental houses and used by hundreds of film makers without an awareness of the color shift. Perhaps the shift from lavender to heliotrope went unnoticed by the client or it very likely didn’t matter in the long run what the true color needed to be. In any case, where it became really apparent and of considerable importance was in corporate logo colors. These colors were clearly important to the end user and that fact alone has changed everything. CRI is now a constant element of promoting the new LED products. I never see a promotional brochure from any manufacturer, in what ever country the product comes from, that CRI isn’t in the literature somewhere. It has become as important as “brightness.”
Empower Your Lighting Arsenal!
Because of this factor I added a new meter to my arsenal. I now have an incident, a spot, a color temperature, and a CRI meter. The meter I purchased was the UPRtek 350, from Taiwan, since it was the first one I actually saw. It also tells me color temperature, Lux, and position on the spectral graph. I now never think of examining a product without testing its light with all meters though I must admit that the CRI meter is the one I use the most these days especially if I’m considering purchase. There are a number of other companies manufacturing these CRI testing instruments and so far they all seem somewhat expensive, however, I think that will change with time.
They are as follows:
(1.) Lighting Passport…………… Allied Scientific Pro
(2.) CL-500a………………………….Konica or Pro-Life
(4.) Spectra Rd Express……………BW Tek
(5.) Chroma -2 LCD…………………Lisun
Now there are probably more meters than this but these should give you some choices to look at. These are mostly meters that Labs use when manufacturing their products and the end users would for the most part use to verify the viability of the brochure information. I actually discovered that I couldn’t tell the color shift accurately with my eyes alone and was often surprised at my results when testing lighting instruments that I had used for years in the past. It was a great awakening for me as I am sure it will be for all of you.
-Michael Rogers, Lighting Constultant & Educational Outreach