Asahi Pentax Super Takumar 55mm lenses compared

[pentaxpete]

Here are Two Asahi Pentax 'Super Takumar 55mm lenses' The one on the RIGHT is the 'f2' version I was given off a jammed S1a. The LEFT one is the original 55mm f1.8 off my 1961 'Asahi Pentax S3' I noticed that on the f2 lens I could move the aperture PAST f2 and the aperture inside opened UP a fraction ! Maybe those f2 lenses are actually the f1.8 ones which Asahi Optical thought were not sharp enough so called it 'f2'

I took a couple of TEST shots with the f2 lens at full aperture on some grotty 1999 dated Kodak PJ800 film rated 100ASA

[Sciolist]

They are essentially the same lens Peter, except the f1:2 has thickened front beauty and rear locking rings, and an additional fixed aperture ring (of f1:2) at the diaphragm. As you say, the iris will actually go larger, but it slips behind the fixed aperture when doing this. I've had them both apart to have a look.

Asahi produced the 'cut-down' version of their Spotmatic, the SP-500, which was also a bit smoke and mirrors, as the missing 1000th of a second shutter speed option was actually there, just not marked on the dial (or calibrated at the factory - who knows). This is a guess as I've not looked into it, but perhaps they wanted a 'cut-down' lens for their 'cut-down' Spotmatic.

EDIT: This may suffer from confirmation bias, but looking at the camera manuals provided online by Buktus, the 'budget' SP500 and SP1000 models are shown in the main fitted with the f1:2, while the standard SP is shown fitted with the f1:1.4.