Sunday, November 16, 2014

Infrared Flash Triggers

Photo #1
Long Ago, In A Galaxy Far, Far Away...Optical slaves triggered by Infra Red (IR) triggers were the working person's answer to trigger multiple flashes. The "slaves" were photo sensitive devices that connected to flash via the hot shoe, an auxiliary PC connector (Nikon), or a dedicated interface (Vivitar), and would fire the flash whenever there was a sudden change in the lighting. This could be a camera mounted speedlight which served as the "master". Politically correct photographers replaced the master/slave terminology to controller/remote, but you get the idea. While a standard flash could be used, IR filtered flashes became the better alternative because their output (usually) wasn't bright enough to affect the overall exposure of the photograph.

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.
Photo #2
For this post, I started by making a series of selfies: first without glasses, and then with them. I used a Nikon D70 with the shutter speed set to 1/2000 of a second and an aperture of F 5.0 (Photo #2). The initial setup was with a Nikon SB-26 aimed toward the ceiling. A second light, a Nikon SB-800 directed towards some reflective foil placed on the floor, provided the fill from below. Both speedlights were set to the built-in SU-4 (optical slave) mode, and positioned in locations that were far away from the lens axis, resulting in a of photos with no glare. This first shot illustrates some rather deep shadows beneath the nose and chin, but you can see in a cropped closeup that there is indeed a catchlight. Of course, I look like I could use some sleep!

Photo #3
Glare spots on glasses are caused by light reflecting off the glass and into the lens. If you can position your light sources away from the lens axis you can eliminate, or at least minimize, any light bounce-back. This high light placement (overhead ceiling bounce) simulates the sort of light that might come from skylights in a large building, while the catchlights  suggest a shiny floor covering (Photo #3). You may notice a tiny red dot above my left eye. I'll get to that later.

Photo #4
This cropping from the first image (Photo #4) shows the catchlight from the light bouncing off of a piece of foil placed on the floor. You'll notice that it isn't a point light source, but rather a large shiny spot. The foil covered about three square feet. Had the reflector been larger and/or closer to my eyes, the catchlight would have been much larger.

Photo #5
There is one problem when using any of these IR triggers. Since the "master" light is usually aimed along the lens axis, there will be a reflection when you photograph shiny objects. While not visible in the selfie sans lunettes, it can be clearly seen in this shot (Photo #5, arrow). Sure, you can easily clone the spot out in post production, but you'll need to examine each image carefully, as glare spots may appear in parts of the photo you might have overlooked. You might be able to avoid this by using the SB-50 and pointing the head upwards, but that won't do much good if you're photographing outdoors.

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.

Photo #6
The MPEX Translator Hack Outdoors: I digress: For a final selfie, I put a 24mm prime lens on a D70 body, set the white balance to daylight and screwed a 30 Magenta filter onto the lens. An MPEX Translator and a 1/2 power manual Nikon SB-800 were mounted on the camera  and pointed away from me and toward the key light and would serve as my triggering flash. This combination gave me the all-speeds synchronization flexibility I would need. Key light was a Nikon SB-700 with a full green (fluorescent) filter attached and set to 1/2 power. The sky, tinted by the 30 M filter, took on a distinctive glow, while the speedlight with full green filter complimented the 30M filter on the lens to give the flash-lit foreground a normal color balance. Exposure information: Shutter set to 1/800th of a second, aperture set to  F 5.6, ISO at 200,  Daylight white balance preset with a 30 Magenta Filter mounted on the lens. The flash was clipped to a handy street sign using a Justin Clamp. The whole filter / white balance thing was a Joe McNally trick, dating back to his film days. I was pleasantly surprised (Photo #6) by the results!