Let's try something new!
As previously mentioned, I was out in Sequim, WA last week to teach a lighting workshop. I stayed overnight at a friend’s place and about 15 minutes before we had to drive over to the workshop I decided to try to make a photo of some hummingbirds flying around the deck. I grabbed one of my Interfit Photographic S1 battery operated strobes out of its case along with its standard 7” reflector and a light stand. I set it up about 3 feet from the bird feeder and then popped a Canon EOS M5 camera onto a tripod with the 70-200mm f/4 IS L lens and a cable release. In just a few of minutes I captured some photos and then had to quickly pack up and head to the workshop (more on the workshop coming soon). For these the flash was in manual mode with the power dialed down to its lowest setting (2.0). The S1 uses IGBT technology* to control the flash, so dialing down gives the shortest flash duration to help avoid motion blur. The camera was also in manual mode and the settings were ISO 100, Shutter speed 1/160, and aperture f/6.3
No, these aren’t the best hummingbird photos. If I were to do this again I would give myself more than 15 minutes and would use at least 2, possibly three, lights for more dimensionality. I would also set up a backdrop behind the birds (where the third light might be used). Here the backdrop was a stand of dark trees about 60 yards away that went completely black. For this morning I was mostly interested in seeing if the flash could capture the wings of the hummingbirds and I think they did well.
In lieu of the mediocre photograph, let’s make this a learning experience.
High Speed Sync?
Some might ask why I used normal sync at 1/160 shutter speed instead of putting the flash into High Speed Sync (HSS) mode. In my experience, HSS is great for matching the flash to the ambient light to photograph at larger apertures (f/4 to f/1.2) to get limited depth of field in an outdoor flash photograph (I didn't need that here, I actually wanted a smaller aperture for more depth of field). But it doesn’t help with freezing motion. Here is a series of photos made with a Canon 430EX II speedlite in normal and HSS modes where you can see what happens to the motion using HSS to photograph a spinning fan.
Notice that at normal sync speeds, even as slow as 1/15 second, the flash duration is fast enough to freeze the motion of the spinning fan blades. As long as the room is dark enough, the ambient light won't affect the photo and the short flash duration becomes your effective "shutter speed" even if the shutter is open for a full second or more. When you get into the HSS zone there is a lot of blur, even though the shutter speeds are faster.
How Flash and Shutter Speed Sync
If you are not familiar with High Speed Sync, what it does is pulses the flash rapidly during the exposure to enable it to synchronize with the moving blades of your camera’s shutter. In normal sync mode you press the shutter button, the first curtain of the shutter opens, the flash fires, then the second (rear) curtain closes. When you go above your camera sync speed (which could be anywhere from 1/60 to 1/250 second) the first curtain opens, the second curtain starts to close, then the flash fires.
If you are just a step or two above your sync speed you get a dark band across one edge of your photo. At higher speeds the flash doesn’t register at all, as the second curtain starts closing as soon and fast as the first curtain opens.
High Speed Sync fires a series of lower powered flashes in perfect synchronization with the moving curtains so that the image looks like it was made with one flash.
Downsides to High Speed Sync
The series of flashes, while being great for letting you photograph at wide open apertures, does have some downsides. The most noticeable is the reduction in power output. Normally the strobe fires and needs a second or two for the capacitors to recycle and be ready to fire again. In HSS the flash doesn’t have any time for recycling, so it puts out a series of very low powered flashes. The light usually has to be close to your subject. You will lose a stop of power every time you double the shutter speed above the sync speed. The second downside is that it doesn’t help much with freezing action. Third is that it goes through batteries quicker. And fourth is that over time the rapid flashing can lead to a lower life expectancy of the flash tube. A note on that, though, is that I have some studio flash units here that are close to or even more than 40 years old and the flash tubes are still working on them (but they’ve never been used for HSS, which didn’t exist 40 years ago).
*IGBT = Insulated Gate Bipolar Transistor
Different flash technologies go about controlling power output and flash duration differently. Large studio pack and head systems usually control power by switching banks of capacitors on or off (capacitor switching). Lowering the power on the pack will shorten the flash duration.
Until recently, most monoblock strobes would vary the voltage of the capacitors (voltage lowering) to control power. In these lowering the power leads to longer flash duration with some change in the color temperature of the light.
IGBT units have constant voltage, but have the ability to shut off the flash tube (tail trimming) when the desired amount of light has been emitted. Here flash duration gets faster as the power is decreased. Color temperature should be a little more consistent at different power levels and by cutting off the tail of the flash the ability to freeze motion is increased. When using IGBT flashes, going to half power or lower gives the faster flash durations.
DISCLOSURE: I am part of the Interfit CreativePros Team.