I recently purchased the Canon EOS 3 and 550 ex about 2 months ago. Whenever, I put the 550 ex on the camera or use the adaptor (2)cord, I noticed there is no preflash when I push the shutter button half way. My 430 ez's pre-flash works all the time when I push the shutter button half way. I've tried it in all the modes. The manual states the preflash will fire immediately before shutter release and the main flash. (I can't see it) I even adjusted the mode on the flash itself. The camera custom functions are set: F1-1; F9-1; F10-3; F13-1. Also, when setting the flash mode E-TTL is displayed, but the manual refers to E-TTL (or ATTL) does the camera select ETTL or ATTL? Should I be concerned? I love the EOS 3 and 550ex. The ECF is great and I wear glasses (-6.75)! Thanks a lot for your help!! Tom

-- Thomas S. Cuchara (cthomusa@hotmail.com), April 22, 2001

Answers

"I noticed there is no preflash when I push the shutter button half way..."

The 550EX pre-flash will fire upon the full depression of the shutter button, not halfway.

Test the pre-flash by doing the following: 1. Set the flash to 2nd curtain sync. 2. Put the camera in TV or M and choose a longer shutter exposure (at least 1 second should do, but a longer exposure should really make it obvious). Don't worry about the exposure being correct, this is only a test. You don't have to have film in the camera.

Fully press the shutter button. You should see the preflash, and then the second flash at the end of the exposure. If you do not see the pre-flash, make sure that the flash is mounted firmly in the hotshoe, make absolutely sure the flash is set to E-TTL and not TTL, and double check that the flash is set to 2nd curtain sync. If it does not work after this, you should get it checked out by an authorized canon repair shop.

It is very, very difficult to see the pre-flash at a normal sync speed (1/60-1/200) with first curtain sync.

-- Roger S. (rashrader@hotmail.com), April 22, 2001.

Pushing the FEL button on the top of the camera will also activate the preflash. Anyway, the newer E-TTL system uses the main flash tube for the preflash, and the camera reads the preflash itself. It does this so fast that you can't even tell that there was a preflash most of the time. The only time it is obvious is with the rear curtain/slow sync that has already been described. Once in a while, you will see the preflash just before the mirror blackout in the viewfinder.

-- Brad Hutcheson (bhutcheson@iname.com), April 22, 2001.

Hi Thomas, I don't think you should to be too concerned about the preflash when you use normal flash sync speeds. It happens so fast that you will not notice it. It works in the following sequence: (1) When you press the shutter button fully, it will first fire a pre-flash, (2) then the reading is metered by the camera and the CPU calculates the required main flash exposure, (3) then the camera shutter opens and (4)the main flash fires the right amount of light. All this happens very fast that you won't be able to discern the pre-flash with your naked eye. The great thing about this E-TTL flash metering is that, it will account for the available lighting, the preflash lighting and the focus point selected. The flash will correctly expose with emphasiz weighted on the selected focus point.

When you use a type A camera such as the new EOS-1V or EOS-3, the flash will automatically switch to E-TTL mode because it recognises the camera correctly. When you use older type B cameras like EOS-10, it will automatically switch to TTL mode. When you use a camera like EOS-1N, it will switch itself to A-TTL mode. The last 2 modes (TTL and ATTL) are older flash metering methods and less effective.

Hope the above answers your questions. If you are interested, you could try out the new 420EX flash, which is cheaper, smaller and slightly less powerful, but packed with useful features (although not as many as the 550EX). One of the features it has, is the ability to be set as a wireless slave unit, controlled by a master 550EX. The 420EX is good enough for many applications, and it also has E-TTL and TTL functions, and I am sure you will love the 550EX & 420EX combo!

-- Anthony Wong (anthwo@hotmail.com), May 03, 2001.