Science Buddies: Focusing Your Flash for 'Freezing' Motion

Here's an interesting flash photography project. With an inexpensive Fresnel lens, you can concentrate the light from your flash. You'll be able to shoot with a smaller aperture and a shorter flash duration. This will give you a greater depth of focus and will allow you to 'freeze' motion at higher speeds. The trade-off is that the light will be concentrated toward the center of the frame. This project shows you how you can investigate that trade-off and find out how you can best use your flash for 'freezing' motion.