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Dedicated Flashes

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March 13, 2002

(1) Manual:
You will likely not encounter this type much because of their age and I only mention it because they're still occasionally found used. These have a completely fixed light output, much like flash bulbs. Light reaching the film is controlled by adjusting the lens aperture based on flash power, film speed and subject distance using a "Guide Number."

(2) Auto:
These are a refinement of a manual flash with a sensor built into the _flash_ unit to "quench" its light output when enough light from it has reflected back into the sensor. These are non-dedicated and can be used with any camera with a hot shoe. Typically the lens is set to a specific aperture based on film speed. On more sophisticated models a switch or button on the back of the flash that allows selecting two or more lens apertures. This is selected first, and then the lens aperture is set to match this. If you look at the shoe on the flash, it will have a single center contact. This is the one used to "trigger" the flash. There may be a light on the back of the strobe that lights up or blinks for a short time after the flash is triggered to indicate its sensor received enough light for a "proper" exposure. With these flashes, you won't get any information about flash status in the camera viewfinder (on, ready, exposure OK, etc.), only on the flash itself.

Among non-dedicated flash units you can use are the Sunpak 383, Vivitar 283 and Vivitar 285. I rate the Sunpak 383 and Vivitar 285 about the same in features, build quality and durability. The Vivitar 283 is the "little brother" of the Vivitar 285 with fewer features. I also rate the Vivitar 285 a "best buy" among non-dedicated flash units. It has the most features at the lowest cost in a decent quality flash unit. It's one of the reasons the 285 remains the first choice by professionals (especially photojournalists) for a "generic" on-camera, non-dedicated flash. None of these will assist your cameras AF system though and you may have to manually focus it in low light.

(3) TTL or TTL/OTF Auto:
These are the "dedicated" flash units you asked about. Instead of using a sensor in the flash, it uses the metering built into your camera to control how much light the flash emits by quenching it. The metering and light measurement is done "through the lens" on your camera (TTL; OTF = off the film, which is a specific type of TTL metering). To do this, the shoe has more than just the one center contact, usually between three and five depending on camera system and flash. These additional contacts are used by the camera and flash to communicate with each other. They are called "dedicated" because each camera system is different in the number of hot shoe contacts, their exact position in the hot shoe (except for the common, large center one) and how they are used. To use a dedicated flash on your Rebel, it must be made specifically for use with it.

"Best" dedicated flash is difficult to define. There are different power levels and other features. Higher power and more features means higher cost. Among the Canon flash units you can use are the 220E Speedlite and 380EX Speedlite.

There are other companies that make dedicated flash units you can use with the Canon EOS Rebel G. Among them are Metz which makes professional grade flash units. To make them compatible with different camera systems, a special module with the hot shoe foot slides onto the bottom of the flash. Metz makes a module for very nearly *every* camera system. For your use, I would recommend looking at the Metz 32MZ-3 (the "-3" supports TTL control and AF; the "-2" does not support AF; the "-1" is a non-dedicated version). The proper module is the SCA 3102 or its predecessor the SCA 3101.

Although more expensive, there is also the Metz 34AF-3C and much more expensive Metz 40AF-4C. These do not need the module; they are specifically made dedicated for the Canon EOS system (the "C" at the end of the model number indicates its for the Canon EOS).

I presume you are looking for a "dedicated" flash. Take a look at the two Canon Speedlites I mentioned, and compare flash power, features and cost with the three Metz flash units.

-- John

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March 14, 2002