Ever since I got my first SB800, I’ve been intrigued by the idea of using its RPT mode for some unique concepts I’ve thrown around in my head. The RPT, or Repeating Flash, Mode acts as a strobe light that you can configure. You can tell it how bright to flash, how many times to do it, and the speed in which they occur. It’s pretty nifty but takes a little bit of toying around with to discover its strengths and weakness. After running an experiment shooting in RPT mode, I’ve discovered its limitations as well as its uses. We’ll cover that in a little bit, but first lets look at how you actually set the thing up.
Now, you can do this in one of two ways: you can either place the flash directly onto the hotshoe of your camera, or you can use one of the various Nikon TTL cables to do the same thing but have more choice over where it sits. However, you cannot use RPT mode in any other fashion. Unfortunately, that means no PocketWizards or eBay triggers. You can use Nikon CLS to trigger more than one, but you’ll need more than one SB-800, and that can get costly.
So, you have the flash connected to the camera using one of the two options available, and you hold down the select button on your camera, go the the upper right screen and set your flash to MASTER RPT. Click select again to confirm, then either wait for the screen to change or hit the ON/OFF button to force it to chance. You’ll then be greeted by this screen:
Looking at the left side, here you have three different groups (A,B,C,), or four if you count the master, the power setting, and the repeat settings. The first two are obvious, though the power settings need to have a small disclaimer. Though you may not think 1/128, or even 1/32, is not a lot of power, once you start popping a number of flashes over the length of your exposure (and you’ll need a reasonably long one for this whole thing to work) it tends to really light up the area. Take note of that when planning your shot.
Then we have the less obvious repeat settings. You have two numbers. The first is the number of times the flash is going to “repeat”, or strobe. The second number is how fast it is going to pop those strobes off. The lowest you can go is 1Hz, which is one strobe per second. The highest you can go is 100Hz, but there are some limitations to that (more on that later). But the concept is, the higher your Hz number, the faster it is going to strobe.
For instance, above here we have 20 x 20Hz. That is 20 strobes at a speed of 20 strobes per second. So the length of time it will take for the SB-800 to fire off all of those 20 strobes is 1 second. If we increased the number of strobes to 30, making it 30 x 20Hz, it would take the flash 1.5 seconds to fire off all 30. Concurrently, if we set the flash to 20 x 10Hz, it would take 2 seconds to fire off all 20 strobes because the flash is only firing 10 per second. Make sense? Good.
In case you find yourself hitting the max strobes allowed for a certain setting, check out the Nikon SB-800 manual on p. 48 (p.54 of the pdf) to see the max settings allowed for a given situation. Also, be careful not to fry your flash. There are certain limitations to how many times you can set it off within a given time period safely. Peruse the manual for that info as well.
Well, since most people don’t have any idea how fast that is in real world terms just talking about it, I decided to provide some examples of what various settings look like photographed. For these examples I used a shutter release cable and stopped the exposure once the strobes were complete.
3 x 2Hz @ 1/128
This is a pretty slow setting. We’ve got 3 strobes at 2Hz (2 strobes per second) at 1/128 power. This provided three frames, which you can see by me holding it, throwing it up and catching it.
3 x 6Hz @ 1/128
Here we have a bit more speed. 3 x 6hz means that the 3 strobes are going off for a duration of 1/2 second. It allows just enough time for me to get it out of my hand after reacting to the first strobe.
3 x 10Hz @ 1/128
A little faster now at 10Hz and I don’t have enough strobes to capture it coming out of my hand. Note that I’m not going that fast.
6 x 6Hz @ 1/128
I’ve increased the strobes to 6 and slowed it down to 6 per second. So the exposure above is for one second. There is enough time to get it going up, hitting its apex, then coming back down into my hand. Two problems are now presenting themselves. First, the obvious multiple, overlapping exposures of the hand. If you have one object in your photo that moves only slightly, you will get the same problem. The second problem that is less obvious now but will become apparent when you try to work a photo using RPT is the brightness of the background. The earlier shots were the same distances back and were set at the same power. But now that we’re throwing 6 strobes at it instead of 3, it creates more light, making the background brighter. This becomes a major problem when the background is brighter than the moving subject and your subject is overpowered and can’t be seen. We’ll see an example of that later.
6 x 10Hz @ 1/128
We’ve bumped our speed up to 10 strobes per second and now all 6 flashes hit before the ball begins to descend past it’s apex.
20 x 20Hz @ 1/128
I decided to bump it up a bit more and show the range of what this can capture. The max it can go at this power setting is 24 x 100Hz. However, we now can see even more clearly the problem so many strobes. In earlier pictures the ball was clear, yet now it looks looks see through. The background was exposed so many times with nothing in front of it that it is now brighter and shows through the ball. The only way to overcome this is to take pictures in front of something that absolutely absorbs all light, or to make your background a VERY long field or open area during a pitch black night. You’d be surprised at how far that light can cast. However, if you can find a dark enough background, you see here that you can capture a pretty awesome range of motion on one exposure. There are cool possibilities with serious challenges to overcome, and I decided to give it a try.
There is this shot that I have in my head where someone is shooting a basketball and the flash catches traveling the whole way. I ran into problems when trying to create that shot however. The first problem was the overexposure of the background. We played around with different angles but no matter what we still ended up overpowering the subject with the background. Now, I’m sure had I used some snoots or very large gobos of some kind, it might have made a difference. However, I didn’t have any of that there so that will need to be used on attempt #2.
The second problem was properly lighting the ball. Had I been in possession of couple of ladders it might have worked better, but, alas I wasn’t. Yet another piece of gear I will need to properly take this shot. The third problem was the multiple exposure of the person shooting the ball. I think the only way to get them in two, maybe three positions would be to use another SB800 mounted on another camera that would be set off in tandem with the main camera. The second camera wouldn’t be taking the picture, it would simple allow another SB800 to be set off. But that’s another day. Here is the best shot of the evening:
I believe this was shot at 14 x 7Hz @ 1/32, but I’m not quite sure. Either way, you see the inherent problems with a background that is too close. The flash is overpowering the ball in the earlier shots and it’s not until it reach the goal that you can really see it. You also see the multiple exposures of my friend shooting the basket. I’ll consider the shot a successful experiment, but it’ll take some real fine tuning to get the picture I envision in my mind. But I’ll save that for another day. Meanwhile, if you decide to experiment with your own strobe photography, let me know and I’ll post some submissions up. It can fun and rewarding, but have patience. I think we shot somewhere over 100 exposures, making small adjustments here or there and this is the best we came up with, so take your time and work out the kinks.