The CAT System.

We have seen the limitations off full manual flash in earlier posts. One engineering approach to improve electronic flash was Canons CAT system. The idea was simple take the distance information from the lens focusing and assume that the object that is in focus should as well be lighted correct. Then use a big (literally) potentiometer to adjust the flash output.

It worked with cameras that allowed matched needle metering. If CAT was activated the level of charge and the feedback from the focus information moved the indicator needle in the viewfinder, and it was matched by selecting the correct aperture. A good description is on the Mir site.

CAT was introduced with the Canondate camera in 1970 and followed in the FTb, and in the old F1 in 1971, EXAuto in 1972 and EF in 1974. While the first compact cameras with inbuilt flash where introduced in 1977 the pocket camera 110ED from the same year still used CAT with the ED flash. In the SLRs it was phased out by the introduction of the A Series in 1976 and finally died with the introduction of the new F1 in 1981.

The whole concept had a number of important draw-backs:

- The system worked only with a number of dedicated cameras. (We are used to that by now, but at the time it was seen as a restriction.)

- The system works with even fewer flashes. In fact apart from the ED for the 110 pocket cameras there was a model D for the Canonet and the AUTO EX Cameras The only model sold in larger quantity was the 133D which was sold with Cameras like the FTb the EF and the old F1. In 1978 Metz introduced the Ueberblitz CT45. After that date there was really no good reason for anyone to buy a 133D which was embarrassingly the "professional" flash for the old F1. To counter the situation Canon came up with the 500A hammer head style flash for the Old F1 which was a total flop. Very few units were produced and sold and it is rare to find today. In typical Japanese fashion the embarrassment got the silent treatment and there is no hint or mention of the 500A in any official Canon Literature anymore. Some people even doubt that they existed, but there are collectors who have some pieces. (The link seems to be dysfunctional now. Earlier there were pictures. A Japanese ad here.)

-The system worked only with four lenses the 50 f1.4 the 50 f1.8 the 35 f2 and the 35 f3.5. With all other lenses the flash was fully manual like ED above. That was really the nail in the coffin of the whole idea to apply CAT to SLRs. While the system worked reasonably well with compact cameras without interchangeable lenses, I don't know how Canon could ever think it was a good idea for the FD lens system when only two focal length worked. The FD lenses had to be fitted with a flash coupling ring that fitted into the front bayonet. There is a small pin on the focusing ring that coupled into the flash ring. When you moved the focus ring the potentiometer in the flash ring was moved and set to the "right" level. Obviously that works only with lenses with a similar diameter but it was also much more restricted by optical lens design. The same ring only works with lenses where the movement of the focus ring produced similar distance settings and the focus movement was in the same relation like the square fall off of light. That explains why it worked only with few FD lenses. Shortly after its introduction the CAT system started to compete with the first "Computer" flashes that worked with all cameras and all lenses. Specifically after the introduction of the Metz 45er it must have been more and more difficult to sell a 133d and a flash ring to Canon users.

- Another disadvantage of CAT is the method of bringing the flash to the "right" level. Actually it did not! The potentiometer simply set the needle in the viewfinder according to distance and the aperture matched the full blast from the flash. Each shot the energy stored in the capacitor is fully released. The flash recycling times were the same regardless of what distance you took the picture. And they were not too fast.

- The mir site perpetuates one marketing myth, the Canon guys came cleverly up with when the automated flash units started to appear and eclipse sales of the CAT flash units. Which is that the CAT system allows to use the flash before it is fully charged and is therefore quicker. As with all good marketing B*** S*** there is a seed of truth in that you can actually fire the flash before it is fully charged. which frankly is the case with all flashes. (see also measuring the voltage here) . However matching a moving needle as the flash is charging along resembles more a video game and the results as things change while you might recompose or refocus make results even more unpredictable and even more ugly as it might result in over exposure.

At some point of time I intended to buy a FTb and a 133D. Somehow I ended up with the 133D alone. I do not intend to buy an FTb just for the sake of CAT so there will be no experiments. The 133D can be used with any camera as a manual flash with guide number 18. As I have quite frankly enough from manual flashes we move quickly on to the "Computer-Electronic Flash" in the next posting .

P.S. Normally all pictures in the Blog are taken by me. If I ever use a picture from the net in exceptional circumstances I will clearly link to the Source. The Picture of the old F1 with 133D is from here

Correction: CAT was actually introduced a year earlier, than I thought. It came with the Canonet 17 QL (new) in July 1969. This was NOT a laps of memory (come on I am not THAT old) rather than a lapse of research.
The error might be forgiven when I show you how I looked like around 1970 in the picture below: