Optikotechna 75mm f/4.5


I made this enlarger lens into a camera lens using a helicoid and an adapter or two. I am quite happy with my creation, a sharp portrait lens.

This is the same as the Meopta Belar 75mm f/4.5 enlarger lens except that the name Optikotechna was changed to Meopta in 1946. This makes my lens sometime pre-1946.

Originally started in 1935, Optikotechna began by supplying the Czechoslovakian army with various optical equipment. They made darkroom equipment, enlarging lenses, composite lenses, binoculars, rifle scopes, cameras, and slide projectors. During the German occupation from 1939-1945, they were forced to make optical equipment for the German army.

I suspect, though I have not found any sort of serial number guide, that my lens was made for the Germans. I base this idea on the fact that the company started small but really ramped things up during WWII.


The lens is setup with two elements in two groups, very simple construction.

Maximum Aperture: f/4.5

Minimum Aperture: f/18

There is fairly good bokeh with mostly smooth blur and some rounded points of light.

The lens is strictly manual focus after you convert it to work with your camera.


The lens itself has a removable front element, giving you access to the aperture blades themselves. The rear of the bare lens is 23.6mm but it works just fine with M23.5 adapter rings.

To make the adaptor I started with an adapter to convert from M23.5 to M42. Then I could connect the adapted lens to a helicoid. I played around with several helicoid sizes, some getting me to infinity (and beyond) but not very close focus while others only let me focus closely and not to infinity. I settled on a 17-31mm helicoid as the best mix. It lets me get to infinity but still focus closely enough for general photography (approximately 4 feet). The last part is simply an M42 to Nikon adaptor.

To focus closer you just need to zoom out a little further. An ideal helicoid might be 18-40mm or so but I have not found such a thing in my travels.

Once assembled you can put the lens onto your Nikon camera, go into the settings and pick a focal length and f-stop, and start shooting. The aperture is controlled at the front of the lens and there is no communication between the lens and the camera to tell the camera if you changed the aperture.


For spending a few dollars I had low expectations but I was shocked at the quality of the images. They are super sharp and exhibit outstanding contrast. The Bokeh is perfectly fine, too.

This lens conversion uses simple, off the shelf (well, eBay) parts. This is a good candidate for your first lens to try converting into being a camera lens, if you haven't played around with things in this part of the hobby before.

Being f/4.5 you need to use it on a bright day (or bright studio lights, whatever) and I tried it in dimmer light, pushing my ISO, and it was not as outstanding as it was in bright light as the contrast was muddied by the higher ISOs.

The lens is super light weight, the helicoid is easily the majority of the converted lens. So if weight is an issue for you, go with this one.

Also, there are other lenses from Optikotechna / Meopta using the same mount making your new adapter one that can support many small, affordable, lightweight enlarger lenses.


I suppose you could argue the Meopta 75mm lens is an "alternative" though technically it is the same lens just with the newer brand name.

I don't own another normal 75mm lens. I have one for my medium format camera, but that is a completely different ballgame.

Adjacent focal lengths are 60mm and 85mm, neither of which is just a few millimeters away. We are talking greater than 10% difference. That makes this lens an oddball, filling a void in the regular lens series.


Following are some sample photos to demonstrate the power of this type of lens and some general uses which will likely yield good results. If you shoot things like these, then this lens may be a good one to think about adding to your camera bag.

For the following photo I was trying things as the sun was setting, hoping my camera's higher ISO capablities would save me, but a lot of contrast is lost with pushing the ISO to the extreme.

Check out more photos I have shot with this lens in my Flickr Album.