I currently own 2 Yashica and 3 Contax flash units (see picture). These are:
- Yashica CS-201, GN 20, Manual, Auto f4 (100 ASA)
- Yashica CS-221, GN 22, Manual, TTL
- Contax TLA 20, GN 20, Manual (Lo, Hi), TTL
- Contax TLA 30, GN 30, Manual (F, ¼, 1/16), Auto (f4, f8), TTL
- Contax TLA 360, GN 36, lots of features, including stroboscopic
From these 5 perhaps the best bargain in terms of price vs. features it the TLA 30. It is a rather large unit that offers Manual (3 levels) auto (including desirable f8 at 100 ASA) and TTL modes. With a bit of patience you can get one for about $30 in ebay.
A note about the three exposure modes: In manual there is no measurement of the light that comes from the flash. At full power the flash emits its full flash. The user controls exposure by adjusting the f-stop of the camera, based on the distance of the subject from the camera.
In auto mode, the flash measures the reflected light and stops the light when the exposure has been satisfied. Auto mode works for certain discrete f-stops. It is generally reliable and converts vintage stereo cameras to automatic (in terms of exposure).
In the TTL mode, the camera and not the flash measures the amount of light that reaches the film, via a sensor that measures the amount of light reflected from the film. This is equivalent to auto exposure camera operation mode. TTL mode is useful because it will work under conditions where it is difficult to measure the amount of light reaching the subject. This is the case in macro photography. I used TTL flash quite a bit with my Minolta X-700 cameras and it is nice to see it in the Contax 139 and Yashica 103 cameras. My first test rolls with the macro attachment and TLA flash showed good exposures.
If you look under the flash units you will see 2 contacts (CS-201), 3 contacts (CS-221, TLA 20, TLA 30) or 5 contacts (TLA 360). For simple flash operation, only one contact is needed (the one at the center). The 2nd contact lets the camera know that a dedicated flash unit is used, and the cameras when used in Auto Exposure mode, sets the shutter speed at the top synchronization speed (100 for these cameras). The 3rd contact is used for TTL operation. The 2 extra contacts in the TLA 360 unit convey information used with more advanced camera models (so they are not needed for our cameras of interest here)
In addition to the flash units, I have acquire several cables that allow you to use the flash off camera (while maintain TTL operation). I am working on possibly wiring two flash units to work with TTL for macro stereo photography.
Finally, instead of the Contax/Yashica flash units, I can use any of my advanced Metz flash units, but I need the appropriate Metz adapter in order to get TTL operation. The simplest adapter that will work with these cameras I the SCA 380.
I have more information about using electronic flash with vintage stereo cameras in my Tutorials (http://www.stereotutorials.com/)