Nikon CLS (1 of N)
This is the first of a few posts about Nikon's CLS, Creative Lighting System. I've used it on and off for several months with Nikon's SB600 and SB800 strobes. It's pretty powerful, but it definitely also has its limitations, and situations where it is simply not suitable for what the photographer needs.
First off, how it works:
When the shutter is pressed to make the image, a strobe in "commander mode" (either an SB800 or a dedicated SU800 command unit or the built-in pop-up flash in several but not all Nikon DSLRs) sends a rapid burst of flash "command" signals to 1-3 groups of strobes (A, B, C).
The slave strobes are set to slave mode, and receive the rapidfire commands from the master flash, a split second before the shutter opens and the actual image is made. Each group of strobes contributes the amount of light it has been told to send.
The commander unit can select from -3 to 0 to +3 relative contributions for each of the 1-3 group(s) of slave strobes, and the commander itself can either contribute to the scene (if it's an SB800 or built-in pop-up) or not.
The range is pretty good. I've not tested scientifically to see what it's maximum is, but I've used it up to 100 feet in fairly direct "line of sight" to the slave strobes. The strobes need to be able to see and read the rapidfire command sequence just before the main exposure is made.
This is NOT line of sight like an infrared signal, and it does NOT use infrared to communicate about the exposure to the group(s) of strobes. This seems to be a somewhat common misunderstanding about Nikon's wireless iTTL CLS system.
Nikon CLS is pretty smart about managing the overall exposure, but it is often between 1/2 to 1 stop under-exposed for some reason. This can be adjusted with exposure compensation and is then usually consistent for that shooting scenario.
Here's what I've found Nikon's CLS is very good for: studio photography of objects, not involving human subjects. I've found it CAN be OK for some scenarios with human subjects, but there can also be some problems. I've found it can be fine for scenarios where there is some action taking place, but it can also be a tad slow, since the command flashes need to happen just prior to the actual image. The delay, while just a split second, has been noticeable to me for example when I was shooting Highland Dancers the other day, and was not getting the exact moment I had wanted to capture because of the Nikon CLS delay.
More on that, and several related things I've learned about CLS, in the next post.
