IR Options: I pulled the following samples from my equipment closet and found, from left to right: The Nikon SG-3 IR (Infra Red) Panel, the Wein Sync-Link Flash Trigger, and the (discontinued) Nikon SB-50 Speedlight with the IR filter Attachment (Photo #1).
- The Nikon SG-3 slips into the hot shoe and the IR shield flipped down to cover the built-in flash. Synchronization speed is limited by the camera, so Nikon D70 users top out at 1/500 of a second.
- The Wein Sync-Link acts like a tiny speedlight (it takes only two AA batteries) and because it does not have the Speedlight Present (SP)contact, it will fire at any speed. I've done some samples at 1/4000 of a second where the limiting factor was the remote speedlight's flash duration, and not that of the Sync-Link itself. And because it functions like a tiny flash, it is subject to lengthening recycle times as the two AA batteries start to lose their juice.
- The Nikon SB-50 comes with a detachable Infra Red panel that blocks most of the visible light, leaving a red wavelengths to trigger the remote flash units. When used with the MPEX Universal Translator, one could theoretically access any reasonable shutter speed. However, I noticed that the light fell off severely at speeds higher than 1/800 of a second, so I'd consider that the practical synchronization ceiling. Unlike the other two options, the flash head can be rotated to a straight up position, which could be an advantage if you have a ceiling to bounce from. Also, when the SB-50 is set to manual, it delivers a full dollop of light, resulting in depleted CR-123 batteries and increased recycle time, like it or not.
Choices: So here are three available options. The cheapest is the Nikon SG-3, so long as you remember to configure your built-in flash to full manual output. Nikon D70 users will be limited to the native (1/500) top sync speed. The Wein Sync-Link is the most versatile, syncing at any speed. The SB-50 is comparable to the Wein, but I can be recommended its use if you already have (or can borrow) one along with its original IR filter. You will be stuck with 1/500 of a second unless you use a workaround of some sort. I certainly wouldn't recommend buying one because I don't think it's a particularly useful flash for the money.
Some Important Considerations: When going with the optical option, your carefully adjusted multi-speedlight setup can be triggered by any flash in the neighborhood, including those from cell phone cameras and point and shoots. This can drive you crazy in small rooms with lots of other cameras. In these environments radio controllers, or the Nikon iTTL Creative Lighting System commander options, work much better.
Power And Range: While I can't trigger a remote speedlight on Molokai (the earth's curvature gets in the way!) these IR units can be used a fair distances outdoors. For an informal test, I set up an SB-800 in the SU-4 mode on a lightstand in our outdoor parking lot. I set up three Nikon D70s, each with one of the three IR triggering options. On a cloudy bright morning, I was able to trigger the SB-800 at a distance of 25 feet using the SG-3 and the built-in flash, while the Wein and the SB-50 successfully triggered the flash at a distance of 35. Since the slaves respond to the sudden change in ambient light, they would become less sensitive in brighter lighting environments and more so in darker venues, allowing for decreased and increased working distances between the triggers and the remote flashes, respectively.