Sunday, April 22, 2007

Extension tube

When I purchased the Cosina 19-35mm lens from Albert, he added a bonus in the form of a Hoya x2 teleconverter. Unfortunately, it was heavily infected by fungus and thus retained not much optical functionality.

Yesterday, I decided to turn the teleconverter into an extension tube. By taking out the optical elements, the teleconverter becomes an empty tube with male and female lens mounts at the ends – an extension tube.

After prying the optics away from the rear mounting ring, the extension tube performed as expected. However, the optical assembly also included various levers to set the light meter. Various attempts were made to restore the light metering lever, but all failed miserably.

Finally, I gave up on retaining aesthetics. A faulty M42-K mount converter ring was attached to the tube to provide the K-mount interface and metering controls. It’s far uglier than using the shiny original aluminium bayonet mount, but it works better than a charm.

The results are startling:

Super-Takumar 50mm f/1.4, without extension tube

The camera at its closest focusing distance

And the view through the viewfinder

Super-Takumar 50mm f/1.4, with extension tube

With the extension tube, the focusing distance decreases dramatically

And the subject can be seen in much, much greater detail