Vivitar Zoom Thyristor 250

[WetMogwai]

I have a Vivitar Zoom Thyristor 250 that has a switch I don't understand. I've looked for a manual, but I can only find other models. The switch has three positions, M, orange, and green. I assume it has something to do with flash intensity. I attached an image. How do I use this switch?

[Mike Wilde]

M - flash is in manual mode. It will dump all charge and so set f stop of camera to match the distance of the subject you are intersted in pointing this thing at.

Red - set camera aperture to f/8 and the flash will automatically quench part way though it's discharge when it senses enough light has been emitted. Function good to as far away as the distance is on it opposite the calculator dal.

Green - same as red, but f/11, but less effective automatic lighting distance. You gain a bit more depth of field with the red, versus the green.

You have to set the dial to match the speed of film in the camera, and set the shutter seed of the camera no faster than it's synch speed (usually marked in red, or with an X etc on the shutter speed dial of focal plane shutter cameras.

If you have an old rangefinder, etc with the shutter in the lens, the thing will synch at any spped.

Take care to use on X contact; olderish cameras sometimes have an M and X contact. M is for flashbulbs, and will fire the almost intantaneous lighting electronic flash too early. Flashbulbs neded time to reach thier peak light emitting intensity.

Good shooting.

If it works on olne a hot shoe socket then that socket will be an x synch one.

[WetMogwai]

Thanks. I'll try it next time I need a flash, though I hope it doesn't happen soon. I try to avoid flash as much as I can. I like having the option if I really need it, though.

[MattKing]

What Mike said, with one refinement.

You will note that there is an ASA/DIN scale. In the picture, you cannot quite see what it is set to, but I assume it is something like ASA 200.

As Mike said, you have to set the ASA/DIN dial to match the film in the camera. When you do, the dial with the F8 and F11 that Mike referred to will also move, and you will see that the red and green markers will line up with new f/stops. With the new film, you use those new f/stops.

Matt