hi i have a elan ii/eos50 and speedlite 420ex at nite , can the flash range reaches up to 300mm zoom? if yes, use ettl or FP/HP? thanks

-- luic (luicbee@hotmail.com), June 01, 2001

Answers

The 550EX will fully illuminate an image using E-TTL taken with a 300mm lens providing the subject is within flash range. FP flash is also possible, providing the subject is within flash range.

-- Dave Herzstein (dherzstein@juno.com), June 01, 2001.

I think the basic math works like this:

Max guide # of 138 (feet) with 100 speed film, assuming your maximum apeture on the 300mm zoom is 5.6, then dividing 138 by 5.6 = 24.64 (about 25 feet maximum)

Using FP, and a shutter speed faster than 1/125 will reduce the range significantly, and should not be needed since at night, all of the illumination would come from the flash (no blur caused by hand holding).

Using 400 speed film would double your flash range to about 50 feet.

-- kenneth katz (socks@bestweb.net), June 03, 2001.