Nowadays, it’s easy to take autofocusing lenses for granted. However, in the grand scheme of photography’s history, autofocus is a relatively recent innovation. In Canon’s rich photographic history, the EF mount introduced in 1987 likely stands out as the beginning of autofocus for the company. However, Canon’s previous FD mount had a special lens among its manual focus optics, the Canon FD 35-70mm F4 AF, which was originally released back in 1981.
In a new video from Kai W, he goes hands-on with the Canon FD 35-70mm F4 AF adapted to a Sony A1 mirrorless camera. It’s quite the combination of old and new. What’s perhaps most interesting about the video is how unusual the Canon FD autofocus lens is. It doesn’t look like any other lens I’ve seen.
The lens includes a ‘Solid State Triangulation’ autofocus mechanism. This was added to the existing FD 35-70mm F4 lens that came out in 1979. As Canon writes, ‘The incorporation of this function into the best-selling FD35-70mm F4 (June 1979) interchangeable lens brought about automation of focusing for SLR cameras.’
How does SST work? Canon writes:
‘The SST method is a system in which information on the photographed object that enters the sensor through two fixed mirrors is converted into an electric signal and distance is measured by a microcomputer, with focusing performed by moving a distance ring with a motor. The latest fixed imaging device CCD (charge-coupled device) technology is adopted to provide high resolution and a broad dynamic range able to detect low to high luminance, making it less susceptible to the contrast and pattern size of the photographed object and enabling highly precise autofocusing. Also, as the SST method does not have a movable section in the distance measuring mechanism, no vibration or electric noise is caused, which provides high reliability fitting of a high-end SLR camera.’
Yes, you’ve read that excerpt correctly, a CCD. The lens has digital imaging technology to drive autofocus. Given the constraints of the FD mount, the lens required its own power source, which is a pair of AA batteries.
Using the lens has some quirks. The FD system was not designed for autofocus, so you must use a button on the lens itself to trigger autofocus. The autofocus system covers where the zoom ring is located on the non-AF version of the FD 35-70mm F4 lens, so there’s a small lever on the bottom of the AF system component that allows you to adjust zoom. Aperture is manually controlled via a standard aperture ring near the base of the lens.
As you can see in Kai’s video, the AF performance is surprisingly good. It’s not the fastest lens, of course, but it’s neat to see a blast from the past perform well enough on a modern camera. To see more videos from Kai W, visit YouTube.