Build Your Own Flash Focuser: This light weight focuser only costs $5 and can triple the range of your flash.
Shooting hummingbirds is tough. To stop their wings takes a flash duration of 1/12,000 of a second or less. When you're very close to them and stopped down to F18 to get enough depth of field for the entire bird to be in focus, you need all the light you can get. Unfortunately, even zoomed out to their maximum focal length flashes have typical beam spreads of 45 degrees. That means the light you want focused on a one square foot area is being spread over 50 or 60 square feet. Your only options are to push the ISO up (which causes graininess and red artifacts), open the aperture (reducing the depth or field), or slow the flash down to get enough light for a proper exposure (which gives you blurred wings.) Fortunately, there's a cheap and easy solution: a beam focuser.
The one I made out of a 9-inch Fresnel lens ($4 at a Barnes and Noble bookstore - they can also be found in 8x10-inch sizes from scientific supply stores like Edmund Scientific), a small piece of foam board ($1.50 a sheet at Wal-Mart - one sheet's enough to make ten of them. You can even use cardboard.), and a little tape cost me a total of $5.00 and 15 minutes to make. Specific plans aren't necessary, the picture above tells you all you need to know to hammer one out for yourself.
I simply used masking tape to attach mine to the flash head. It's light, cheap, comes off cleanly and doesn't slip.
The only tricky part is deciding how far out in front of the flash the Fresnel lens should be. You want it to focus the beam almost to it's tightest point but be careful not to get it spot-on. If you do then at that distance the image of the flash's diffuser lens will be in focus and the light pattern may not be uniform. For my Canon 580 EX flash a 9-inch separation between the flash and the Fresnel lens worked out perfectly. At this distant the flash's light is focused into a very slowly spreading beam that leaves a 1-foot by 8-inch pattern from 5 feet away or a 3x2-foot pattern from 18 feet. In contrast, without the focuser the beam is 8-feet wide at 5-feet away.
As an example of what flash extenders can do, the pictures below were taken 5-feet away from a clay model of a hummingbird (I call it Frankenhummer, for obvious reasons) at ISO 400 with the flash set at 1/64th power (1/31,000 of a second). The top row (without the flash focuser) from left to right has F stops of F18, F13, and F11. The bottom row (still left to right) is F8 and F6.3. The frame on on the far lower right was taken with the flash extender and the F stop returned to F18.
As this shows it's very effective. (Note: these photos where not lightened or darkened in any way during processing. In fact they were merged into a single frame before any processing to make sure they were all treated equally.)
There are a couple of hazards associated with flash focusers:
1. In close-up shots it's necessary to check that the beam is going to hit the target. It's so tight that it could go right over the top without lighting the subject.
2. Be careful in sunlight: the fresnel lens can focus the sun's light enough to melt your flash or set fires.
There are commercially made versions of flash focusers that are tailor made for specific sizes and brands of flashes available for around $40.00. Here as a few sites that sell them:
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