Sequences with Flash
The Three Kinds of Sequences
These are simply firing a camera rapidly. This is the most common. When used without flash you can just keep firing away, at typically a few frames per second (FPS) with most cameras. FPS is usually specified as a feature.
Flash recycle times are usually a few seconds, however that's when they are used at full power in manual or at their maximum distance. For the past 20 years automatic flashes that don't shoot their full load of power can make their next shot immediately without having to recycle fully. If the flash uses only a small amount of power for each shot you also can shoot with the flash at several frames per second. For instance, if the flash only needs 10% of it's full power for each shot you can make ten shots as fast as you want before draining all the power from the flash's capacitor.
You keep the flash power low by moving closer, using a higher ISO, or using a larger aperture. This is why fast flash sync is important, since the faster sync allows larger apertures for sequence shooting. (more here about fast sync.) Of course you also can dial down the power in manual mode, but that's the hard way.
More powerful flash units can get off more shots before they are exhausted.
After you've made all the shots of which the flash is capable in one burst you have to wait the full several seconds for it to recharge or recycle before you can do it again. Of course as you're shooting it's doing it's best to recycle, too. Don't bother calculating all this. Just shoot away and the flash will deal with this as best it can. If you can't get enough shots in a sequence just get closer, crank up the ISO or open your aperture.
Do this a lot for a long time and you may be able to melt a flash unit. Just feel the front of it now and then and back off if it's getting too hot. Nikon specifies in their user manuals how many full power dumps you're allowed and how long you have to wait for cooling without melting the flash. I find I can do much more than that and my flash still works. I don't worry about this, but I'm not shooting pro sports all day long either. Just be careful.
These shots are rare and usually only seen in sales flyers for flash units with too many features. These show a moving object exposed several times on the same frame with a dark background. These sales brochures usually show something lame like a bouncing ping pong ball or someone swinging a tennis racquet in the dark. Wow.
These strobe modes are where the flash fires many times per second as long as you hold down the flash button, just like repeating strobes on an airplane at night. I find the best use of this feature is if you are transported back to the 1970's and find yourself in a disco. To use this for photography you set the camera on Bulb and hold open the shutter in the dark to get a sequence multiply exposed in one frame. Because the long exposure has to be as long as the sequence I've only seen these made in the dark. Wow.
You can tell I'm not a fan of this mode, which is a popular feature put on more expensive flash units to make you think you need them. Personally I prefer flash units without this feature, since this feature gets in the way when I'm selecting among the modes I really use.
These are seen in action sports magazines like "Snowboarder" where you have sequential multiple images of an athlete pulling an aerial maneuver in front of the same background. These great images are often used to illustrate the steps in a complex move.
These take a long time to composite together in Photoshop. You start with a conventional sequence of rapid fire shots, with or without flash. You then choose one shot as the background image, and of course save a little time by choosing one with the athlete in it. You then select out the athlete from the other images and using layers composite them on top of the background image. It involves a lot of selecting, so these are easiest to do if framed against a sky.