Rangefinders, due to design limitations, have limited close up focusing abilities. Most can focus only up to 1 metre or slightly less. The RF mechanism will not permit easy focusing for closer objects. The separate viewfinder won’t show the correct field- due to parallax. Separate viewfinders also won’t show the FOV change as the focus gets closer: Field of View becomes narrower as the lens focuses closer.

Closeup supplementary lenses which attach to the lens are available, but using them is cumbersome. They require the use of separate framing devices and focus is never exact since focusing requires a conversion table where the lens must be set for each closeup focus setting.

The early SLRs’s touted sales claim was the ability to make close-ups… that was their only selling point because everything else about them was a pain to use. Just handle an Exakta or Contax D, or a Contaflex and you’ll see why RF reigned supreme for years before the introduction of the Nikon F or Pentax HV.

Reflex focusing attachments thus became available for this. These devices convert the RF camera into an SLR. The mirror viewfinder is attached to the lens mount. The extra extension allows the lens to focus really close. With extra bellows, the ability to focus really close even becomes greater. Leitz made VISOFLEX. The Soviets decided to fuse the accessory mirror reflex attachment to the camera and created the Zenit.

This one is the not-so-common Mirax Focabell, made by Miranda Camera. Miranda is a now extinct Japanese camera maker. The Focabell was the only(?) accessory they made for the Leica and its copies. Miranda never made Leica copies; they went to making SLRs right away.

This attachment fits the Leica easily. It will usually fit some of the FED or the Zorki, but because of their non-standard lens mounts, the mirror reflex housing does not always line up properly on them.

I’ve only used this attachment once or twice. I don’t even remember what I took with it…