I just got back from Costa Rica. I planned an exciting photo tour there for next year. I was thrilled to get a picture of the most active volcano in the country, Mt Arenal. The image actually looks much more exciting than the mountain did in reality because of the camera's ability to take time exposures. Just like shooting moving traffic lights at night, I used time exposures (from 30 seconds to 5 minutes) to get streaks of molten boulders tumbling down the mountain. I tried various exposure settings and found that 320 ISO at f/2.8 worked best. For exposures longer than 30 seconds, I used a locking cable release.
I was also able to get a very special series of pictures of an extremely endangered jungle cat, the oncilla, in the Arenal National Park.
My primary goal, though, was to shoot hummingbirds. Hummingbird photography is a serious challenge because the wings are moving at 200 beats per second, and the only way to freeze that motion is with a flash. Here is how I did it:
When a flash is put in manual mode, the 'flash duration' -- i.e. the precise length of time that the flash tube is lit during the exposure -- is about 1/1000th of a second. That is not fast enough to freeze the wings. A much shorter flash duration is required.
What causes a variation in light output from a flash is not what you think. It's not that the flash varies in light intensity, or bright versus darker. Instead, it's the flash duration. When the flash is used on ETTL (automatic mode), the actual flash duration varies. For example, when the flash is close to a subject, let's say five feet, the flash duration may be 1/1500th of a second. If the flash is moved further away, say 15 feet, the flash duration has to be longer -- perhaps 1/500th of a second simply because a greater flash-t0-subject distance requires more light.
With hummingbird photography, I used four separate flash units (Canon 430EX speedlites), and they all had to be outputting the exact same flash duration (otherwise there would be ghosting). Therefore, they were all used on manual mode, not automatic. The way you can shorten the flash duration is by cutting the power of the flash down. For example, if the typical flash duration is 1/1000th of a second on full power, when you set the unit to 1/2 power the flash duration is 1/2000th of a second. Similarly, at 1/4 power the speed becomes 1/4000th of a second, at 1/8 power it is 1/8000th of a second, and at 1/16 power we get about 1/16,000th. This is the setting I used.
Obviously the diminished power setting cuts the light down considerably. That's why the flash units have to be placed very close to the flower from where the birds will be feeding. The two flash units in front of the setup -- one on either side of it -- were about 16 inches away. This close proximity allowed me to use 1/16th power. In addition, I had a flash behind and off to the side for a backlight, and then one flash unit was aiming at the background. I didn't want a black background (since hummers are diurnal), so I placed a 24 x 36 inch print of out of focus foliage behind the flower.
To trigger the flash units, a wireless transmitter is needed. This can be either the Canon ST-E2 (which also works with Nikon) or a Pocket Wizard. The advantage of the Canon unit is price, but the Pocket Wizard allows you to trigger flash units if they are placed directly behind the subject because they work on a radio frequency rather than line-of-sight. If you wanted a direct backlight, the Pocket Wizard is ideal.
At 1/16th power, the recyle time of the flashes was very fast -- about 1/2 second. I could therefore shoot rapidly. It is impossible to see the wing formation of the hummingbirds as they are hovering above a flower because to our eyes it looks like a blur. Therefore, many pictures I took weren't good. The wings were in unattractive positions. I took enough shots, though, that a certain percentage were fantastic.
I was also fortunate on this trip to photograph a rarely seen jungle creature called a paca. It is a relative of the capybara, a South American rodent. This thing looks like a giant rat, and because it's nocturnal I photographed it with flash placed behind the animals (they came out of the night for the food the lodge placed on the ground). I had my Costa Rican driver hold the flash behind the animals because I thought this gave a realistic rendition of an animal of the night.
When I have the dates and the price of the Costa Rica workshop next year, they will be posted on my website and announced in my free monthly newsletter (if you don't receive it now, you can sign up on the home page of my website).
