Canon FD lenses

Canon FD lenses on EOS cameras

One approach to putting an FD lens onto an EF mount EOF camera is to buy an adapter. This is not an ideal solution in most cases because you are faced with a choice between two issues:

A simple mechanical adapter will not allow focus to infinity. In my tests focus farther away than 0.24 meters for a 50mm lens was impossible.
A cheap adapter with an optical element will allow focus to infinity, but with drastic image degradation.

If you only intend to do macro work, loss of infinity focus is not an issue at all, in fact a little bit of extra extension can be a good thing.

Canon once made an FD to EF converter. I was high quality, but also very expensive (on the order of $500). It is extremely scarce. It was intended for use with expensive super telephoto lenses.

Infinity focus

You may be wondering why you loose infinity focus with an inexpensive mechanical adapter. There are two reasons. One is the difference in flange to focal plane distance for the two mounts. In short, EOS cameras are "fatter" than the old FD mount cameras. An EOS camera has a 44mm flange to focal distance, whereas the FD mount lenses are designed for a 42mm flange to focal distance. This is a mere 2mm difference, but it means that you cannot focus to infinity, to do that, the FD lens would need to be moved back 2mm into the EOS body.

On top of the extra 2mm added by the change in registration distance, the converter itself adds as much as 11mm of extension, taking you to as much as 14mm total extension in one case that I measured.

Infinity focus calculations

Adapters with glass

The inexpensive FD to EF adapters available on Ebay sell for about $30 (maybe $20 more than the adapters without glass). It should not take much thought to realize that you are not going to get a precision optical component for $20. What this lens is is a mild negative lens that compensates for the extra extension introduced by the adapter. It is effectively a low power teleconverter. Some people have been entirely satisfied with the results from these devices, but most are not.

Adapters without glass

These sell for $10 or $15 on Ebay. They are sometimes labelled as "macro only" and they are well suited for such use. Hard to go wrong putting a quality FD mount macro lens on an EOS body using one of these.

Aperture control

FD mount lenses have levers on the back that allow the camera to meter wide open, then close down the aperture to take the photo. Unless you want the lens to always be wide open, you need to provide a way to manipulate these levers. Commercial adapters (with or without glass) do this, typically via a ring you turn.

Focus confirmation

If you begin scrounging around the internet for FD to EOS adapters, you will soon discover that they are available with focus confirmation ("chipped") and without ("unchipped").

The two FD to EF adapters that I have on lenses I use for macro work do not have the focus confirmation chip and connectors. I use these lenses in studio situations with my camera tethered to a computer and use live view to focus.

The focus confirmation chip is definitely handy for a lens intended for general use. The way it works is that you turn the focus ring on the lens and when you get to the focus position, the central focus indicator in the viewfinder lights up.

Feedback? Questions? Drop me a line!

Tom's Digital Photography Info / [email protected]