T2i compatibility with old Speedlite 188A? Just purchased a T2i and am really excited to use. 1) Will my very old Speedlite 188A work with the T2i? 2) Is there any advantage to using the old Speedlite compared to the built-in flash? Thanks in advance.
NOTE: It can be dangerous to try old flashes on your T2i. Some old flashes used very high trigger voltages which could damage your camera's electronics.
Information on the web about the 188A indicates is probably safe to use with modern cameras (though you should verify this yourself before trying it). The flash, being a very early design, can not communicate with your camera but it may work in auto or manual mode. Note that auto mode requires you to dial the ISO setting and distance into the flash and then dial the resulting recommended aperture into the camera for a proper exposure. Since the the flash doesn't tilt or swivel, it offers no real advantages to the built-in flash except perhaps for power. I believe this flash will be more trouble than its worth. You might be able to put it to use as a slave flash by using an optical trigger device.
I had the same question, I found that the flash trigger voltage of my 199A was 5-6V. I also am using the following from Amazon to do off camera flash cheaply. Cheaplights NPT-04 4 Channel Wireless Hot Shoe Flash Trigger and 2 Receivers Set for Canon Nikon Pentax
The voltage seems safe. I just got a Canon 188A yesterday, and measured the voltage with a digital voltmeter. It is 4.4 volts, which is perfectly safe. The real question is whether the camera body will talk to the strobe properly and set the exposure correctly. I am still experimenting with that. It seems like the exposure is okay with a Vivitar 28-210mm EOS lens, and too dark with a Canon 28-80mm EOS lens.
"The real question is whether the camera body will talk to the strobe properly and set the exposure correctly."
The only flashes that can communicate with a Rebel T2i or other Canon DSLR to set exposure properly is the Canon EX series or a third party ETTL compatible flash.
I believe the 188a flash, however, has an auto mode which uses a built-in sensor to adjust the flash exposure (it does not really talk to the camera at all except to trigger the flash). This requires setting your camera to manual and dialing in an exposure ISO and aperture (or equivalent) based on subject distance using a chart on the back of the flash. Pick an appropriate shutter speed based on the flash sync speed for your camera model (1/200 sec or slower for the T2i) or slower.
I have used a Sunpak auto flash with various Canon and other brands of DSLRs with pretty good results though it did require much more tweaking (via aperture setting) than when using an ETTL flash.