Meopta was a Czechoslovak national holding company, producing various optical devices.
Enlarger lens was one of the fields they worked on. Some of them has a specialty: has only 4 aperture blades which makes it great subject for building square bokeh lens.
Meopta Belar 50mm f/4.5, Anaret 50mm f/4.5 and Belar 75mm f4.5 are very similar, both has 4 aperture blades, equal focal length and 4.5 aperture. Also both came with 23.5×0.5 mm thread which makes adapting the lens to a modern camera a bit difficult. Please note some of them have 23.5mm to 39mm step up ring included which makes the adaptation even easier, some of them – especially the 75mm – can have more aperture blades depending on the year most probably.
Despite the difficulties it worth to adapt to modern camera for multiple reasons:
- Covers full frame sensor
- Sharp at center
- Has special characteristics
I will focus on mounting the 23.5mm threaded version on Sony a7 camera. You will need these
- Meopta lens obviously
- Slim M42 to NEX adapter
- M42 to M42 17-35mm focusing helicoid
- 42-28mm step down ring
- 30-37mm step up ring – for the lens hood
- 37mm lens hood
For 23.5mm lens the simples implementation is removing the metal ring from the lens case and glue into the 42-28 step down ring. You may need to use sandpaper to remove the inner thread of the step down ring this way make some place for the 23.5mm ring.
Once it is ready, you some glue (superglue or epoxy) to make the fit permanent.
Last thing is to screw together the parts as shown on the following picture:
For M39 thread lens , you can simply use an M39 to M42 adapter ring without any glue.
Meopta Anaret 80mm f/4.5 and 105mm f/4.5 are also good candidate for macro photography thanks to their excellent center sharpness. For that purpose you can use a longer 25-55mm focusing helicoid and a macro focus rail.