Having flashes not pop at at an event while shooting group photos is really aggravating, especially when the Bishop is being kind enough to stand there while this would-be photographer fights with the equipment at hand to at least get some shot worth having…
Not having a budget to acquire real RF wireless remote triggers that support the wireless Nikon CLS protocol has driven the investigation into using alternate means, including the use of wires, to extend the range of wireless CLS (formally AWL per Nikon, a subset of CLS) controlled flashes.
Some perusing of the web turned up this interesting video where an AVR microcontroller was used to trigger an SB-600 flash using a plain old LED, which validated my strong suspicion that an LED could be used to wirelessly trigger a CLS flash.
I only need to locally repeat what the camera sends for each remotely controlled flash; there’s no need to reverse engineer the AWS protocol or even use a microcontroller. A phototransistor, a regular transistor, a red/near IR LED, some resistors and a power source should be sufficient to re-create the CLS master pulses at some remote location. (I’ve not drawn up a schematic yet but eventually I will…)
Here is a photo of the successful first attempt at triggering a remote flash:
The trigger LED, which has a wavelength of something like a 800-900 nm, can be seen just above and to the left of the flash.
Now remote extender and the Picaxe smarty trigger needs to be built into a box/systen that allows the use of ethernet cables to distribute the signals and power to allow multiple CLS and dumb flashes to be used and remotely fired using only the on camera flash as the CLS master.
Last week I got frustrated and annoyed that I’d bought a whole bunch of older style dumb strobes and had used few of them because they lack the remote control niftiness of Nikon’s Creative Lighting System (CLS). Regular slave strobes pop attached flashes when they see the first of the many sent out by the Nikon CLS master. So, I pulled the trigger and ordered parts to make up to three “smart” slave triggers…
I considered using two good old 555 timers to create a delayed trigger to pop the dumb strobes but all the resistors and capacitors it would take to wire those up point to point was a major turn off. I wanted something simple and programmable, so I ordered the 8-pin PICAXE 08M2 microcontroller. It’s a Microchip part that has a BASIC interpreter burned into it. I chose it because the programming cable was simple and cheap, as was the device itself.
I already had a bunch of Infrared phototransistors I’d ordered a while back, so the only thing I really lacked was some NPN transistors, which I picked up at lunch today.
Here is the schematic:
I have not assigned any component values because I’ve only bench tested it, and only at close range that. I suspect R1 may need to be resized to make it more sensitive at greater distances.
Q1 is the phototransistor which forms a voltage divider with R1. C1 and R2 comprise a high pass filter that only lets the CLS master’s flashes through. (This portion of the circuit came from combing the many slave trigger schematics on the web over a long period of time, so I apologize for not having any specific attribution for this.)
Transistors Q2 and Q3 make up a wired AND that pops the dumb flash when Q1 sees a flash from the CLS master and when pin C.2 is high. For the older high voltage strobes, Q2 and Q3 will be connected to an opto-isolating triac.
The current code has flashes LED D1 as an indication that power is applied and that it is alive. Pin C.3 is set up as an interrupt input; when a flash is detected, it jumps to an interrupt service routine that waits a certain amount of time based on the setting of R4. When the delay period is up, pin C.2 is driven high, turning on Q2 for a short period of time. If a flash is detected when pin C.2 is high, both transistors turn on and the connected slave pops. (I can’t post the code at the moment because I don’t have access to it at the moment. I will blog on this more in the future and include the code then. Hit me up if you’d like it sooner.)
The current code turns on pin C.1 during the delay period. On the prototype, there is no LED connected – I had a scope connected so I could see the signal. In practice, R4 can be adjusted until LED D2 is no longer seen in an image, meaning the photo is being taken after the waiting period has expired. This allows for adjusting the delay since the pulse train in CLS is not fixed – it changes depending on what all is configured.
The proof that it works is in the pudding, though. It’s nice to see the signals on the scope but nothing is more satisfying as seeing the dumb slave pop when a real CLS remote would. Here is the photographic proof which includes the prototype itself:
I’d like to make a PCB, but unless I build a bunch of these, it’s probably not worth it. Nor is it worth it to draw up and etch boards myself – I don’t like using the ferric chloride etchant anymore and it’s hard to step back to funky homemade boards after having had real ones made… (Maybe there is a market for kitted up/assembled versions, in which case making a board would make sense.)
I still need to box it up so it’s not so fragile and figure out how I want to power these. I have a bunch of button cells but I’m not sure how long they’ll last even if I turn off or disconnect the LEDs.
Well, not really…
We met this young woman four years ago when she was a freshman. It has been really neat watching her blossom. She heads off to college in the fall. It does not seem like that much time has passed…
We’ve been shooting her senior portraits piecemeal for a while now. Last night was probably the final installment. Stopping by last night with her mother, she pretty much just sat in the chair talking with our children while Jacci took the photos. Here are two of them:
I neglected to take any BTS/setup shots, but there were three lights: A 2 foot square soft box was about 3 feet in front of her on camera right. It had a homemade one-directional grid on it, consisting of 2 inch wide foam core strips running vertically, spaced about 2 inches apart, intended to reduce the spill horizontally but not vertically. The second was a reflector consisting of a 20×30 inch sheet of white foam core on camera left, just outside of the frame. The third light was a flash gridded with about an inch of Coroplast and set on a diagonal from the background about 4-5 feet away to create a splash of light on the background.
Jacci only took something like 24 shots, which included some I took while setting up the lights. I watched her while she was sorting through them afterwards when she kept going back and forth between them. I thought she did not like them so I asked her about it. No, instead she liked most of them and was having trouble picking a couple to post on Facebook. After posting, she further commented that she did very little post processing of them, fixing some facial blemishes and some skin softening. She did very little like with the last living room portrait shoot we did using the homemade unidirectional grid.
I thought I had made a blog posting about it, but it was apparently on our Facebook page instead. I’m reposting it here for comparison:
In this one, there were only two lights: the uni-gridded on camera left and a bare flash on the lower shelf of that table pointed up at the background.
The other difference in these two sets of photos were that I was using battery flashes instead of the fixed power 45 Watt-second slave bulbs we’ve typically used. I think less power in the soft box makes the contribution of light bouncing off the walls much less significant. The slave strobes require shooting at F10-F13 versus F5 with the battery flashes.