In part 1 we landed on the Godox SL200W as an optimal LED source, when you factor in price, convenience, and power. In part 2, we saw that there are optimal beam angles to consider when creating soft light. We also, saw the magical properties of magic cloth diffusion.
The next factor to consider in our soft key light is the output. LED lighting manufacturers continue to push lights with more and more output. Lights like the Aputure 600D and the Forza 500 push into the 1.2K HMI territory. While this is exciting. As we’ve seen in part 2, the photometrics may be misleading. These newer lights use sleek new reflectors that output more light but give you a narrower beam. While narrow beams are useful for some applications, they are not optimal for our case of creating a large source of soft light within a small footprint.
Learning how to test lights or any other gear can really save you money down the road. Despite what the marketing says about CRI and output, you really need to see what works best for your situation.
The best way to test the amount of output you need is to use a light meter to take measurements of situations you most often find yourself in. I know as a one man band, I’ll never be competing with the power of the sun in a daylight exterior by using another light. Direct sun can output as much as 9300 foot candles. Even Hollywood productions oftentimes will choose to shoot when the sun is lower on the horizon. It’s also more efficient to work with bounce and diffusion to manipulate the sun rather than to try and overpower it.
In interiors, sun can play factor by blowing out windows that are in your scene. You should always do a tech scout of your scene to see what the windows are doing. Is it a south facing window with direct light coming in or are you shooting at high noon where the sun is blasting off of surfaces causing highlights to be blown out. Again, as a one man band the best way to add production value is to avoid competing with direct sunlight.
However, there are still many situations where a powerful key light can save you. For instance, shooting a wide shot with a high key look. You would need a light that can illuminate a scene rather than just a subject or talent. The source would need to be large enough that it can be backed away from the field of view and still appear soft. The source would need to bright enough to dial in your subject to background contrast ratio for a high key, natural look. Another situation is where the context determines that you shoot with windows along the edges of your frame or in the background. A key light in these situations allows you to stop down on your exposure to retain the highlights in your image and still get correct exposure on your subject. In these cases, you really want the right quantity (foot candles) and quality (softness) coming from your key light. You want a light that reproduces the color of daylight so that you can "extend" the light coming from the window and use your soft source light to wrap around your subject.
I aimed for an output that approximates 100 foot candles of light, 3 feet away from the source, in this case the magic cloth. That gives me headroom to just slightly overpower a north facing window or an overcast day. A lighting setup that gives me a lot of output gives me flexibility to handle a wide variety of situations. If I want to shoot something more stylistic, moody, or narratively driven I can always dim the key light to approximate the ratios I need.
Since I was able to purchase a trio of used Godox lights, I experimented with using two lights on a baby double header. I was able to get an even spread of light across the 6x6 surface area of the Magic Cloth. The double light set up was able to give me my 100 FC from a distance of 6 feet. That amount of light really does enable me to shoot an interview with a wider shot, while still maintaining a soft quality.
Stay tuned for Part 4 where we will look at our final qualification- simplicity in set up.
Motivation for a Soft Key Light