Hello,

Having purchased a Speedlite 540 to use with my EOS100, I still haven't quite figured out how to adjust the combo to provide fill flash only. I understand that Nikon flashes usually come with a fill program, but it doesn't seem to be the case with Canon.

Could someone fill me in, please?

Thanks

-- Soren Kvistgaard (fotogeniet@mail.dk), December 08, 2000

Answers

EOS Speedlites don't have a specific "fill-flash program", because this electronic "logic" is integral. That is, as long as the flash is in a TTL mode (either A-TTL or TTL), fill-flash will be controlled by the TTL system (in any CAMERA shooting mode, such as P, Av, Tv, M, etc.), and this system will apply what it "thinks" is the correct amount of fill-flash, and once that amount of flash has been delivered, the TTL system will then quench the flash accordingly. After you've shot a number of rolls of slide film with fill-flash provided by your 540EZ (and initially using NO flash exposure compensation), you should have a preliminary idea of whether you like the uncompensated results. If your results frequently look a bit over-exposed or the resulting fill-flash often looks artificial to your tastes, then in the future, you'll want to experiment with selecting some degree of negative (-) FLASH exposure compensation. Conversely, if you want more light, then experiment with selecting some degree of (+) exposure compensation. After gaining more experience, you should begin to recognize situations where you are likely to want (-), (+), or no flash exposure compensation. I've been using EOS gear since 1994, and with either the 540EZ or the 550EX Speedlites, I happen to often prefer using some degree of (-) flash exposure comp. when using these flashes for fill-flash, i.e., anywhere from -1/3rd or -1/2, to -3 stops of FEC, depending on the circumstances. Only by experience will you learn when FEC is likely to be helpful.

-- kurt heintzelman (heintzelman.1@osu.edu), December 08, 2000.

To add the technical to Kurt's explaination...

If the ambient lighting is above EV10 the camera will start providing some automatic reduction in flash exposure. For every stop above EV10 the flash will be set an additional -.5 stops of flash exposure, until the lighting level is above EV13. So in most daylight situations the camera imposes a -1.5 stop compensation to flash exposure.

Some like it the way it is, some want less flash, and a few what more. Fortunatly, the 540EZ provides a way to induce flash exposure compensation, since your camera doesn't.

You can do the same flash exposure compensation with the built-in flash since the EOS 100 will control that. The same auto reduction in higher light levels applies to it. As far as I know the EOS 100 is the only EOS camera that will do flash exposure comp with the built in unit but not with an external one.

-- Jim Strutz (jimstrutz@juno.com), December 08, 2000.