Leica «Focus Adapters» aka «Focus Checkers» — LTM Only, Or Do Also Leica M Mount Versions Exist?


Oct 20, 2016
By happenstance, a couple of years ago I won a CORFIELD Periflex «Focus Checker» aka «Focus Adapter» for a really good (low) price.

Except the correct nomenclature of the item, the seller was describing the item quite correctly, but nevertheless I was the only bidder, IIRC.

Here some links having pictures of apparently two or three versions of the item in question — mine is slightly different again, BTW:

  - Framing & Focusing - Antique and Vintage Cameras




So my questions are:

1. What is the standard terminology of that sort of item?

2. Did anyone make a similar item (of that handiness!) for Leica M lenses?

Thank you :)


Jul 7, 2010
I have a "Focus Previewer" for Nikon F mount that is a stand-alone, ir manually out it on the lens and remove it. It was probably intended for "Mirror-up" lenses, was with the 2.1cm F4 that I bought.

I have a focus previewer for Leica that allows the previewer and camera body to swing in and out. It is for close-up work only, an extension is built into the swing mechanism. The Leica viewer shown in the first link (Focaslide) is also intended for close-up work. I need to find mine...

The most useful that I've found:

Subscribe to see EXIF info for this image (if available)
My method of setting the shim. by fiftyonepointsix, on Flickr

Came with the Canon body cap, but not sure who made it. It is a previewer with magnifier.


Jul 7, 2010
At home now- the Nikon device is labeled a "Field Previewer for Nikkor lenses" product number 2305, which is hand-written on the box. This think is circa 1962.

The Leica device is made in California and is called a "Speed-O-Copy", will have to get a picture of it. Same idea as the Leica device, but simpler.

This would not be too hard of a device to make from a loupe, matte focus screen- such as a Nikon Type B2 for the FE2, and an extension ring.

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