Mirrorless Cameras and Legacy Lenses – Part III

Photo showing depth of field

In a previous post, I shared a brief history of the Jupiter lenses, a Soviet-made series that have become popular with mirrorless camera enthusiasts. There are several models, with some — notably the Jupiter 8 — often available very inexpensively on eBay. Intrigued by the possibility of expanding my lens arsenal with an inexpensive but useful lens, I did some shopping, and ended up with one of the 50 mm Jupiter 8’s for about $50, including shipping. Not bad.

The lens arrived in just a few days, and I was eager to try it out. It seemed to be the lens I had bid on (not always the case on eBay!) and was relatively clean with signs of long-term but reasonable wear. The only physical damage was a slightly-bent filter ring — not too hard to fix. I screwed the micro four-thirds (m43) to 39 mm screw (m39 or Leica screw-mount) adapter on, and mounted it to the camera.

The problem - soft infinity focus
The problem – soft infinity focus

A few shots later, it was clear that there was a problem. The lens was not focusing at infinity. For distances of 30 feet or less, it looked good however, and I decided to see what could be done. Back down the rabbit-hole. I quickly learned that there are several models of this lens made over at least a couple of decades, as the basic design was fitted to a number of camera models. The problem appeared to be that the focus adjustment did not move the lens unit close enough to the camera sensor.

Diving a little deeper, I discovered that the Jupiter-8 lens was manufactured to two different focal-length standards, Zeiss and Leica. They vary slightly, and the lenses one finds on eBay may be made to either standard. The eBay listings rarely mention this difference. What can be done? There are a couple of possibilities: change or add shims within the lens, remove “stop” elements within the lens to allow a slightly greater rotation of the focus ring, or manage the focus problem by using smaller aperture settings when shooting near infinity focus.

A very good description of Jupiter-8 lens service is available at www.pentax-manuals.com, so I decided to see if I could adjust my lens. It is slightly different than those models described in the service document, but I was able to take my lens apart, make small changes and re-assemble it without too much difficulty. In the end, I removed one of the stop screws which allowed slightly greater focus rotation. It didn’t completely correct the problem, but it was greatly improved. Going forward, I plan to get some better tiny screwdrivers, and go a little further in the lens disassembly. I think there are adjustments that can be made in the lens unit itself. The pictures below show my process.

Photo showing depth of field
Dreamy depth of field

Was it worth it? Yes. Although the lens isn’t perfect, it’s great for portraiture and other work where a dreamy-deep depth of field is desirable. I also got a chance to begin learning about the internals of lenses on a model that is fairly simple and not too much of a loss if I didn’t get it back together. Also, I was able to remove old, sticky grease and replace it with fresh lithium grease. The lens operates much more smoothly now. If you end up trying this yourself, a really tiny screwdriver and a lighted magnifying glass are essential. Some of the parts are very small!

photo of Remove the 3 screws and keeper ring
Remove the 3 screws, keeper ring and lens mount ring
Photo of Remove the 3 screws and focus ring
Remove the 3 screws and focus ring
photo of lens body with helix against stop pin
lens body with helix against stop pin. The guide pin was removed from the hole on the right.
photo of Lens body with stop pin
Lens body with stop pin after the helix is removed.
photo of Stop pin removed
Stop pin removed and helix re-installed. You may have to experiment replacing the helix as it can be threaded onto the lens body  in four different positions.
photo of Lens body with helix and guide pin
Lens body with helix and guide pin replaced. Replace the lens, mount and keeper rings.

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