m42 Pentax Super Takumar 50mm f/1.4 lenses
Decades ago when my first SLR broke (a Miranda Sensorex), I was loaned a Pentax Spotmatic with a 50mm f/1.4 lens. I eventually replaced my Sensorex with a Nikon but for years delayed buying a 50mm Nikon lens because I could not find one that was as sharp as the Pentax. I discovered that the lens I had been using was the 8-element version of the m42 Asahi 50mm f/1.4 Super Takumar and had a reputation for being one of the best 50mm f/1.4 lenses ever made.
The 7-element version is also a very good lens but is not as good as the 8-element version. One major problem with the 7-element lens is that it has a radioactive lens element that gradually turns yellow.
Other than the image quality, the two ways to tell the two lenses apart are:
a) The 8-element version has the infrared focus mark located to the right of the f/4 mark.
b) The diaphragm switch on the 8-element version is marked with “A” and “M.”
The 7-element version has:
a) The infrared focus mark located to the left of the f/4 mark.
b) The diaphragm switch on the 7-element version marked with “AUTO” and “Manual.”