Vivitar flash

Hi all:
I just came across a Vivitar Auto Thryristor 2800 flah.
I have a question or maybe is two on one: In the front of the flash there is a kind of sliding tab labeled red dot, M and blue dot and a small round window under this sliding tab, what is this used for?
Is going to used with my Canon EOS 850 film camera, that is about 15 years old but still in mint condition.
Thanks

Julian

I'm not 100% positive without seeing it, but the sliding switch should put it into one of three modes. The two colored dots correspond with different output levels for shooting at different distances. This is usually labeled on a distance scale on the back (or sometimes the side) of the flash. The round window would have to be the sensor that figures out how much light output (within the given range of Red or Blue) is needed.

The previous poster is correct and M stands for manual [ full flash output ]. Be careful with the sync. voltage. I use one of these flashes and the sync voltage is approx. 80 volts, so I use a safe-sync with all my digital cameras. I'm not sure what your camera is rated for so you better check to be safe. Hope that helps.

Quote:

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Originally Posted by gimp

The previous poster is correct and M stands for manual [ full flash output ]. Be careful with the sync. voltage. I use one of these flashes and the sync voltage is approx. 80 volts, so I use a safe-sync with all my digital cameras. I'm not sure what your camera is rated for so you better check to be safe. Hope that helps.

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If you look here it shows that your camera will support up to 250 volts sync voltage, Jeff

http://photonotes.org/cgi-bin/camera...a4=*&camera5=*

Thanks everybody, this answers all of my questions; I love this camera, it saw my two kids grow up, also all , or almost all of my vacations all over the Caribe, Africa, Mexico, and Colombia.
It's still in mint condition with the exception of some dust in the viewfinder prism.
As all of you know, this is a film camera.

Thanks again

Julian