Take a look at these 2 pictures. Yes, I know, they are poor shots, directly lit by the flash (oh noes!) and don’t even seem to have a purpose. They look like multi-exposures but they are not. They might have been done by strobe-painting, where you would keep the shutter open for a few seconds while firing a flash manually.

In fact, these 2 shots were done using the stroboscopic function of the Sigma 500DG Super flash. Of course, I was aware of this function from the first day I purchased the flash, more than 2 years ago. It took me this long to move the ol’ ass and get some experimenting done. Once more, I ignored the user manual and went to figure this on my own. Not a very difficult feat considering most modern interfaces are fairly intuitive.

What are the uses of this function? Well, obviously you can show objects in motion, provided said motion happens during the time your shutter is open and within the space that you have framed with your camera. You can also obtain a sort of stop-motion animation of a moving object in a single frame. This can be useful for various scientific purposes but it can also be used to create some very artistic shots. In short, there are more applications for this function than can be listed here.

Now what would be the main advantage of using a flash with a stroboscopic function rather than manually painting the subject with flashes? Easy: using the dedicated function, you can set the frequency and intensity of the light, as well as the number of flashes, straight from the Sigma strobe. Impressively, the Sigma 500DG can fire at frequencies between 1Hz and 199Hz. Power can also be varied between 1/4 and 1/128. The number of flashes also varies between 100 at 1Hz and 2 at 199Hz. Realistically speaking however, I really wonder if the AA batteries would be able to recharge the flash quickly enough.

So here’s how to use this function of the Sigma 500DG Super in 6 easy steps.

1. After turning the flash on, cycle through the different modes by pressing the Mode button, until you get to the Multi mode. You should see something like in the following image:

2. Press the Sel button to change the default settings.

3. The first option that blinks is the frequency. Raise or lower it with the + and – keys.

4. After setting the frequency, press Set to move to the power setting which will start blinking. Again, change this with the + and – keys.

5. Pressing Set again will allow you to change the number of flashes fired.

6. One final press of the Set button and you have finished setting it up.

Now you can start shooting.

Bear in mind that this function is active only while the shutter is open. As a result, you should calculate the number of flashes and their frequency such that they occur within the timeframe when your shutter is open. For example, you can have a 2 second exposure, set the frequency to 2Hz and the number of flashes to 4 and the strobe will fire 4 times during those 2 seconds. However, if instead of 4 you set the number of flashes at 2, the strobe will fire 2 times during the 1^st second of exposure and not at all during the 2^nd second. Yeah, it sounds a little bit tricky and it took me a while to figure out but it really makes sense if you think about it.

Now here’s another thing. I mentioned at the beginning of the last paragraph that the flashes will fire only while the shutter is open. How this works is that the first flash will go off the moment the shutter opens. So if you have the above scenario with a 2 second exposure, 2Hz frequency but 6 flashes, what actually happens is that a total of 5 flashes will go off. Here’s why:

Second 0: 1^st flash fires

Second 0.5: 2^nd flash fires

Second 1: 3^rd flash fires

Second 1.5: 4^th flash fires

Second 2: 5^th flash fires

The 6^th flash won’t fire because it would need a 2.5 second exposure for that.

All this probably sounds cool and all but I’m afraid I’m gonna have to burst your bubble.

Everything is well and dandy as long as the flash is mounted on the camera but who wants that in this day and age? Unfortunately, the whole stroboscopic function won’t work with the cheap eBay remotes I’m using. So the only solution would be to use an off-camera flash cord, with specific contacts for your type of camera. That would be the only way in which the camera can communicate to the flash that the shutter is open. Wireless remotes just send a triggering signal without additional information and the Sigma flash doesn’t recognize that as a long exposure (or any length for that matter). The main reason this won’t work for even a single exposure, however, is that the Multi exposure mode of the Sigma 500DG Super does not equal Slave mode. So the strobe simply has no idea that something external is trying to trigger it. End of story.

What about more expensive wireless triggers such as Pocket Wizards? I don’t know about those but I have a feeling those won’t work either.

In the end, the only solution that I can see is the good old off-camera flash cord. Problem is, the one from Canon costs $50 and is damn short making the whole exercise pointless if you need to keep the flash more than about 2 feet away from the camera.

One more thing that I would like to add is that I just tested the Sigma 500DG Super at very high frequencies (100Hz and 199Hz) but low power (1/128) and it works without any hitches. The sound it makes at these frequencies is almost eerie. Hopefully I will post a couple of movies of this once I get my Canon G9.

This entry was posted on Tuesday, December 11th, 2007 at 10:56 pm and is filed under Lighting. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.