Digital Video - January 2008 - (Page 46) DV 101 For these two images, a custom lightbox was created to demonstrate the differences in color temperature. In both, the left side of the box is lit with a daylight-balanced source (5600ºK) and the right side is lit with a tungsten source (3200ºK). A black card divider prevents any spill from either side. The gray-scale chip chart, tennis ball, red plastic disc, blue cylinder and white background are identical on each side. The only difference between the two images is the white balance setting in the camera. In the left image the camera is set to daylight (outdoor) color temperature while in the right image the camera is set to tungsten (indoor). mination, small tungsten fixtures with full CTB quickly become completely ineffective. The flipside to this technique is to convert the daylight to tungsten (5600ºK to 3200ºK) by putting CTO (Color Temperature Orange or Correct to Orange) gel on the windows to filter out the blue wavelengths of light and let through the orange/red. The tungsten lights can now be used at full strength while the CTO gel simultaneously reduces the intensity of the daylight coming through the windows (by 2/3 stop), in essence, killing two birds with one stone. You can even get CTO combined with neutral density gels (ND0.3, ND0.6, ND0.9 or ND1.2) that will correct the light and reduce the light even further, making the balance between exterior and interior easier. For most cinematographers, this is the preferred method. It does require considerably more gel and can often be a challenge if the windows are tough to access, but it is a more efficient way to get the most from your small tungsten lights. Another method is to bring in lighting that is already balanced to 5600ºK. For many, HMI sources are cost-prohibitive, but there is daylight-balanced fluorescent lighting that can be incorporated as soft interior lighting. General ubiquitous “cool white” fluorescent tubes are naturally close to 5600ºK, but have a lot of green in them as well. It’s a better idea to locate some specialty tubes with a During this month, high CRI (color rendering index) of 95 Jay will be discussing or more to help eliminate the green. much more detailed lighting scenarios and tips Although those are more expensive in his DV101 Blog. Visit than standard “cool white” tubes, DV online. they are considerably cheaper than 46 dv january 2008 HMIs. LED fixtures are another option, although they are not cheap, either. Many LED fixtures come in 5600ºK varieties. Beyond color, latitude is the next major problem. Balancing intensities is a challenge for anyone working on a budget. If you have a subject in front of a window during daytime, the exposures out the window can be so much higher than the exposures inside the room that you’ll either see nothing but pure white outside the window or you’ll see nothing but shadow people inside. The three ways to deal with this situation are to: A) pick the best exposure to balance the extremes, B) cut down the light from outside, or C) raise the light levels inside. I discussed option C above through using additional light, but you can also use bounce boards or reflectors to make efficient use of the natural light and balance out the latitude a bit. Bouncing light is a great technique for not only a creating soft source, but optimizing what is already there. Bounce materials range considerably, with each texture creating a different quality of light. The smooth surface of foamcore will create a “harder” bounce light and return a high percentage of the illumination to the scene. This is great for taking light from the window and bouncing it into your subject to fill them. A piece of beadboard or Styrofoam will also serve, but the broken-up (beaded) surface is more diffuse and will return a softer light with a lot less efficiency in intensity — meaning you’ll lose more light off beadboard than you will off foamcore. Many people use silver reflectors, which have an even higher efficiency of return than foamcore, but can produce some hard, spotty results and need to be used carefully. Inexpensive car sun blockers can be purchased at auto parts stores and used as flexible bounces. I’m a big fan of mirrors. I always carry a package of 1’x1’ mirrors with me. They’re fairly inexpensive and can be found at any home supply store — usually in the tile department. You can get some nail-on baby plates (flat plates with 5/8” spuds) or configure your own mounting system to position the mirrors on stands. These are great for taking light through windows and bouncing it to highlight areas around the scene. I also carry some plastic mirrors (intended for use in showers) that are lightweight and can be taped up easily. These kind of compact mirrors allow me to multitask either existing lighting or what small fixtures I may have. In a perfect world, any solution for balancing color temperature should also work as a solution for balancing latitude. DV www.dv.com JAY HOLBEN http://www.dv.com http://www.dv.com
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