External flash & consumer-grade digital camera, how-to. : eBay Guides

EBay member "Wouter" writes,

"I read your review for the HP945 [a great 5 mega pixel, but without a hotshoe –Ed.], and I was interested in a schema for a remote trigger. Could you post it to me, please?"

I'll do better than that, Wouter.

Here's how you can add an infinite amount of external strobe and flash accessories to your hotshoeless, relatively inexpensive, consumer-grade digital camera.

You'll find the results are surprisingly good.


There are special challenges in flash photography for the budget-savvy digital photographer. For one thing, most of the optically-triggered “slave” systems currently so abundant and cheap on EBay lack components essential to their proper function with most consumer-grade digital cameras. With few exceptions, the majority of inexpensive digital cameras available today use a “pre-flash” to calibrate the white balance and set a variety of exposure parameters before they fire the flash while recording the image on the CCD and save it as your picture. And then there’s the pre-pre-flash: a burst of light emitted for the purpose of contracting your subject’s irises, thus obscuring their shiny red retinas. An ordinary “fire when you see a burst of light” trigger will not know the difference between these antecedent events and the one that comes when the shutter is open. The result is premature flashing, which is just as dark and ugly as it sounds.

Fortunately, there are ways of getting around this electronically. Chipsets exist which can be told to hold their charge until they’ve seen two or three pre-flashes, and then fire the external equipment on the one that counts. You can acquire this technology quickly and expensively, or you can apply a little elbow grease and save some dosh. Money not an issue? You can buy remote flash triggers that use a moveable optical sensor which one mounts right up against the camera's (i.e., any camera's) on-board flash unit. Better still, buy a good digital SLR and skip all of this gadgetry.

Alternatively, if you’ve got a surplus of elbow grease and some aptitude for photoelectronics, you can build a “digital-ready optical slave trigger” from scratch: Magnus Strömqvist has courteously provided a schematic on his website. If you’re less adept with a soldering iron, consider the Sunpak Digital Flash Adapter. For about $20.00, you can purchase one from Adorama (where it’s cheaper than it is at most EBay vendors), and put your external, hot shoe-mounted flash back into synch with your camera. There remain, however, these two issues with which you must contend: the effect of the camera-mounted flash on other optically-triggered equipment, and the changes to exposure necessitated by your having overridden the camera’s pre-flash settings.

Unless you don’t mind wiring all of your external strobes to the digital flash trigger through a hotshoe PC adapter, you’ll want your other equipment to be triggered either by a battery-operated radio slave, transmitted from your adapter’s hotshoe, or by ordinary, non pre-flash detecting optical slaves. Why? Because they’re cheap, easy and portable. You can buy a fistful for twenty bucks on EBay and then hot-shoe or PC connect the suckers to your assorted fills, hair lights, back lights and et cetera, but you’ll have to make sure that they don’t pick up the pre-flash. And then there are the adjustments to the white balance and exposure that the pre-flash system was supposed to have automated – you’re in charge of all of that now.

Adjusting the white balance for flash photography is easy. Take your digital camera out of “automatic” mode and set it for “sunny outdoors” and you’ll be in the right area of the chromosphere for a flash-illuminated subject. Exposure is a little trickier, but manageable. Even if your consumer-grade digital camera keeps shutter speed and aperture as mutually exclusive manual parameters (such that it will let you adjust one or the other but not both), it’s effectively hamstrung when the flash is operating. If you take over the aperture manually, flash mode will lock the shutter speed to 1/60th of a second, giving you considerable power in choosing the right f-stop for correct exposure. Hence, the usual rules apply: meter carefully and bracket your exposures. Feels more like photography already, doesn’t it?

But what about the effect of the pre-flash on the optically-triggered slaves you’ve distributed like so much popcorn throughout your studio? How will they be protected from your digital camera’s pre-flash? Worse: suppose you’d like to mount a wide lens or a ring flash on the barrel – the camera’s on- board flash will cast an ugly shadow over these accessories. For these reasons you’ve got to obscure the thing such that it can deliver its signal to the digital-savvy optical trigger but no further, and here’s how.

You will need:

A few feet of hockey tape which you can get at a sports equipment store. In Canada, where I live, everybody has 8 rolls of the stuff kicking around. You can use electrician's tape too, but I found it to be too gooey -- the stickum tends to spread out the more the thing is handled. Hockey tape, however, holds its adhesive within a cloth-based foundation and will keep its shape even if you have to high-stick somebody with your camera.


Also, get a cheap fiber-optic novelty lamp (from a discount department store or garage sale preferably, although you can win one for ¢ on eBay). Waste no time in disposing of the lamp base: the bulb, housing... often there's a translucent little wheel that makes the thing change colour – fire all of that into the trash. All you want is a short bundle of fiber optic cable.


See how neatly and efficiently it carries the photons from my desk lamp around a corner when I bend just a few of the strands into the light? You'll also want 6” of rigid wire to hold it in a permanent U-Bend - use a coat hanger.


Now jam a ping-pong ball at either end and wrap it in hockey tape. Trim holes at either end for your camera’s on-board flash and the sensor for an electronic flash trigger, respectively. Put in a wee elastic to hold the balls to their respective sensor/on-board flash and you're done.



The finished product should look something like this:



This Rube Goldberg arrangement works because, within the Newtonian space of 1/60th of a second (the shutter speed typically assigned in flash photography), there are whole universes of Einsteinian space in which the flash on your camera may communicate with the digital-savvy slave trigger, and for it then to send a signal to a transmitter or hotshoe-mounted flash. It is not, of course, a good way to conserve battery power, as it wastes considerable energy in firing your on-board flash (along with pre-flashings), the majority of which will have no effect whatsoever upon the resulting image, thanks to your obscuring "fiber optic conduit." Nonetheless, for about one-fifth the cost of a low-end DSLR, a good consumer-grade digital camera (such as the HP945 pictured here) and some ingenuity can yield surprisingly good results.