Rebel XT with Speedlite 155A

Discussion in 'Canon EOS' started by haltedsisyphus, Apr 26, 2007.

  1. I recently received a 155A and AE-1 as a gift. I'd like to learn how to use the
    manual flash on my Rebel XT rather than the AE-1 so I don't have to buy extra
    film and develop several rolls of bad pictures during the learning process.

    According to Jim Strutz, the voltage of the 155A is fine for EOS cameras.
    http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=002VKJ
    http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=009Oce

    But according to Kevin Bjorke's site, the 155A may be unsafe.
    http://www.botzilla.com/photo/strobeVolts.html

    I've tried the combo, and it works, but I have read that the bad effects of
    mismatched voltage can be subtle at first and/or cumulative. Can anyone else
    weigh in on the safety of this combination?
     
  2. I'd guess that it's safe. Though the XT max sync spec is 6v or less, the 155a voltage is reported to be under 8v and I don't think that's going to cause any problems.

    You could use a "safe sync" adapter, but I doubt that it's really necessary. If you're the sort of person that worries a lot, it might be worth it just for peace of mind.

    You may want to read this: http://www.bobatkins.com/photography/eosfaq/eosfaq24/3flash.html#q21

    Canon actually said that the 155a was OK with early EOS bodies which had the same 6v sync spec as the XT does.

    The EOS 1 series, as well as the 20D/30D and XTi have a sync spec of 250v rather than 6v since they use a different type of flash sync circuitry.
     
  3. Measure the voltage with an inexpensive volt-meter from the hardware store (centre pin on bottom of shoe should be +, contact on side of shoe is ground). This is the only way to be 100% certain of your particular unit's voltage.
     
  4. Thanks Bob and Michael. I won't worry about it anymore, but still might pick up a cheap volt-meter next time I'm at a hardware store. It sounds like something that might come in handy someday anyway.
     
  5. You may need something better than a *cheap* voltmeter. You need something with at least 20,000 ohms per volt. Less than that could give you a false sense of security, as it will tend to draw down the voltage artificially. There are people claiming the only way to really tell what's going on is with an oscilloscope. While that is probably technically true, I doubt it makes a difference to the camera.

    But I still hold that 8 volts is safe on any Canon camera. They have a lot more toleration for voltage built into then than that. Lots of people have been using +20 volt flashes on older EOS cameras without issue, not that I would risk it, but it does show that Canon's 6 volt max is probably conservative.

    But on another note, I thought the XT was one of those newer models that allows up to 250 volts, like the XTi does. Not that I can remember for sure, but I just thought it was.
     
  6. Ah yes. According to http://www.bobatkins.com/photography/digital/eos_digital_rebel_xt_vs_20d.html

    "The Digital Rebel XT maximum sync voltage is also 250v, not 6v [...]. Canon have recently stated that the Digital Rebel XT does in fact share the 250v sync voltage."

    Good news. I'll refrain from buying any kind of voltmeter until I find a need for one. Thanks Jim.
     

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