Making MF lenses Autofocus!

You may recall that till the time autofocus (AF) technology reached us, the MF (manual focus) lenses were the only type available.

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Even now many covet the latter since they were solidly and robustly built (mostly with metal) and will last a lifetime. There is no doubt that most will not match the current lenses for absolute sharpness or low aberration levels, but many showed an interesting ‘character’ in rendering and have a ‘charm’ of their own. The problem with us photographers is that, as we relied more and more on autofocusing, we forgot the art of manually focusing. Consequently, the use of MF lenses slowly went out of vogue thus depriving many of us of the joy of using them.

So, is there a solution? Yes, indeed. Though the title of the article sounds unbelievable, this is very much possible due to modern technology. And it is not with just one brand of lenses, thus opening endless possibilities. How this is possible is the subject of the article. Read on to get a glimpse of this interesting development.

AF lenses have the needed mechanical and electronic hardware built in to support autofocusing. However, the actual detection of the subject and the in or out-of-focus status are determined by the camera body. The latter then decides how to drive the lens to get accurate focus. This is done in one of two ways depending on the type of lens. In the older method, the camera has a motor to drive the lens focusing mechanism (essentially a helical) through a pin-type linkage (often called the ‘screwdriver’ coupling). This is now an outdated technology. In the modern method, the motor is inside the lens itself, and the camera in this case just sends the needed signals to the lens via a set of contacts (Picture 1). These are interpreted by the electronics of the lens and then the in-built motor drives the focusing mechanism to achieve the correct focus. This is by far a faster and superior method.