The Praktiflex of 1938 was the first SLR to use a screw-mount lens (Pic: Danalor 01/Wikimedia Commons CC-BY-SA 3.0) In 1938, as war clouds started to gather in post-Depression Europe, designers at ...

The major exception is that it is incompatible with Nikon's F-mount DSLR range, whether you have an M42 adapter or not. The lens is notable for having been engineered to have a 'swirly' bokeh ...