Canon flash query?

[puddleduck]

I was doing some macro yesterday with a Canon EOS 3 (film SSR) + a Canon 105mm macro lens + 540 EX speedlite.

On my Nikon cameras, when I have to use flash (either onboard or with a Speedlight), when flash is engaged I get a fixed shutter speed (1/60 for onboard, usually 1/250 with a Speedlight) regardless of aperture, and the flash takes care of the exposure.

I can't seem to get this to work on a Canon - shooting aperture priority, 100ASA Ektachrome, pushed to 200ASA my shutter speeds were very low, at f/11, so I wanted to use flash to add some light.

However even with the 540EX turned on, the EOS 3 didn't seem to "know" about the flash, so I was getting very slow exposures - shutter was about 1/8th and didn't seem to take into account the flash at all.

I think this is probably a sync setting somewhere but I can't find it!

I've had similar problems with a Sigma macro-ring flash as well.

Any Canon-ites who can tell me what I'm doing wrong?

[Samiad]

At a guess, because I have no idea about the EOS 3, it's a custom function. All the Canon's I've laid my mitts on have a CFn that will change how the flash works in Av mode. With it 'on' it forces a 1/200 shutter speed and uses E-TTL to correct exposure. With it 'off' it meters for ambient background lighting and provides fill flash if needed.

Also, I believe it was a 540EZ speedlite, not the EX? EZ flash does not communicate E-TTL through to the body, only TTL metering. I believe someone might correct me on that assumption though. Something to take note of.

[Matholwch]

When shooting with a flashgun, I usually set the camera into manual mode, and set the aperature and shutter speed to whatever I'm happy with, and use the flashgun to 'fill in' the rest...
Not sure with the whole CFn for flash on/off which Samiad mentioned (must read the manual some day on CFn).

[puddleduck]

Thanks Guys, I'll have a look at CFn tommorrow. I think its probably a 540EZ, not EX!

I tend to use your method Matholwch sometimes as well, you can pretty much select any manual exposure you want, and the camera figures out the flash - very clever!