Star-testing a Super-Takumar 50mm f/1.4 lens

 The 8-element Pentax Super-Takumar 50mm f/1.4 lens was manufactured between 1964-1966.  According to internet lore (likely accurate), Pentax pulled out all the stops to manufacture this lens and sold it at a loss in order to claim "King of the Hill" status.  It is venerated in the Pentax community.  My copy has a low serial number and was therefore probably manufactured near the beginning of that time window.

I chose to do these tests with the lens mounted on a micro-four thirds E-M5iii camera.  This was a wise choice, because the results show that the edge performance on a full-frame (35 mm, e.g. Sony A7iii) camera would likely be bad. (actually, I take that back.  The Sony has a thinner sensor stack, so that might make a difference.) FWIW, the K&F Concepts adapter easily allows infinity focus, confirmed with a Bahtinov mask, which is greatly appreciated.

Here are two images of the lens mounted on the camera:

 The following images illustrate the performance over a series of f-stops: 1.4, 2, 2.8, 4.  Wide open, this lens is useless (actually, horrible) for astrophotography.  On a micro-four-thirds sensor, it becomes usable only at f/2.8.  These images show the stars in the handle of the Big Dipper setting over the Bristol Head ridge line.  Based on star separations, the actual focal length of this lens is 51.2 mm.

f/1.4 (ugh. yes, focused with a Bahtinov mask)

 

f/2.0, getting better, but still bad

 

f/2.8, acceptable

f/4.0, best, but slow

Some more pics, all taken at f/2.8:

Sagittarius

 

Corona Borealis over Bristol Head

 

In the image above, the position of the recurrent nova TCrB (T Coronae Borealis) is circled. This nova has an assumed eruption period of 80 years, which would make the year 2026 the next expected date. So far, nothing.

 

Fomalhaut (Alpha Piscis Austrini) over the southern flank of Snowshoe Mountain.

 

Lyra.  The Ring Nebula (M57) is circled near the left edge.

Conclusion: This is not a good lens for astrophotography.  Back in the day (film photography with manual-focus lenses) it was generally known that most lenses performed best when stopped down two or three stops from wide open.  The results here illustrate that quite well. This lens was great in its time, but modern lenses with special-dispersion glass and aspherical elements are are far superior when used wide open.

 Finally, an image taken the same evening after the moon rose above the ridgeline of Snowshoe mountain.  Not the Takumar.  A Panasonic Leica 9mm, live-comp 1-hr exposure.

Leica 9mm @ f/2. 1-hr.