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Sean Carpenter | profile | all galleries >> Equipment >> the Normal Lens Shootout >> Round 1 >> Match 2: (8) SMC Pentax-F 1:1.7 50mm vs. (9) Asahi Opt. Co. SMC Takumar 1:2 55mm tree view | thumbnails | slideshow

Match 2: (8) SMC Pentax-F 1:1.7 50mm vs. (9) Asahi Opt. Co. SMC Takumar 1:2 55mm

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The second match of the Normal Lens Shootout, pairing the 8th-ranked SMC Pentax-F 1:1.7 50mm against the 9th-ranked SMC Takumar 1:2 55mm, should have been a close match. If the first pairing in the Normal Lens Shootout - of the first and sixteenth-ranked lenses - was won by a surprisingly narrow gap, this pairing is outright indistinguishable. As a matter of fact, these two lenses performed so similarly that I was reduced to purely subjective reasons for selecting the winner.

Physical Comparison

There are some obvious differences between the 30-year-old Asahi Optical Co. SMC Takumar 1:2 55mm and the half-as-old SMC Pentax-F 1:1.7 50mm. The SMC Takumar 55/2 is a manual-focus, manual aperture M42 screw mount lens. The fully-automatic bayonet Pentax-F 50/1.7 is four lens generations more advanced. The SMC Takumar 55/2 has a 5mm longer focal length and is half a stop slower in maximum aperture. The Pentax-F 50/1.7 has a minimum aperture of f/22 whereas the SMC Takumar 55/2 only stops down to f/16.

However, as different as the two lenses are, they share some important similarities. They both are roughly the same size. Both weigh 200g. Both focus to nearly the same point. They both have 6 straight aperture blades. The front lens elements are similarly sized, both having Pentax's Super-Multi-Coating, which provides excellent light transmission and protection against flare.


The SMC Takumar 55/2 is metal with a rubberized focus grip. The grip is necessarily made for manually focusing, so it is wide and focuses smoothly across the range. The metal aperture ring moves smoothly and clicks into place smartly.

The lampshade-shaped SMC Pentax-F 50/1.7 was the start of the end of aesthetics at the Asahi Optical Company. It is made from dull gray plastic with the focus scale behind scratchable clear plastic. The aperture ring has a build proportionate to its lack of intended use. The notched focus ring is better than the later-generation FA lenses, but is not really intended for manual focusing.

Physical Usage

Using both of these lenses on DSLRs, the obvious advantage goes to the Pentax-F 50/1.7. As a modern lens, the F series supports all the automated features of the K10D, including open-aperture metering, exposure compensation via e-dial, MTF, and auto focus.

The SMC Takumar 55/2 is an M42 screw mount lens, and as such requires an adapter to fit K-mount cameras. It has an Auto/Manual switch that, when set to the Manual position, allows the lens to stop down as the aperture is changed. With the lens in this stopped-down mode the K10 can then meter in Aperture Priority, with the obvious trade-off of the darkened view. However, as with all M42 lenses, the DSLRs will only support center-weight or spot metering, Aperture Priority or Manual modes, and exposure compensation requires pressing two buttons simultaneously. For the duration of this matchup, the SMC Takumar 55/2 required +1EV compensation compared to the Pentax-F 50/1.7 to produce similar shutter speeds.

Side view of both the SMC Pentax-F 1:1.7 50mm, left, and the Asahi Optical Co. SMC Takumar 1:2 55mm, right.
Click here for to see the front elements.

Optical Comparison

This series of 100% crops (click on the photo for the full-size version) of both lenses between f/1.7 and f/8, shows demonstrates the uncanny similarity in out-of-focus rendering between the two.
Click here for a gallery of samples of these two lenses.

I was able to deduce only two differences between the images from both these lenses. The first difference is that the Pentax-F 50/1.7 produces slightly cooler (temperature-wise, more towards blue) images than the SMC Takumar 55/2. In the digital age, and shooting RAW, color corrections of this type are much easier to do than in the film era, so the slight temperature differences in images does not weight into my liking or disliking a lens.

Color Fringing

The second difference, and the only pronounced one, was color fringing at wide apertures. High-contrast subjects produced a purple/blue color bleeding in the Pentax-F 50/1.7 at f/1.7 and f/2 at light/dark transitions. The SMC Takumar 55/2 produced a slightly less noticeable red fringe in the same scene. Neither result is particularly disturbing or intrusive, and both can be addressed by the same post-processing.


I could detect no difference in sharpness at equivalent apertures between the two lenses. I would suspect most noticeable differences would be from focusing errors rather than the lenses themselves.


There is virtually no difference between these two lenses in their out-of-focus rendering. The crops attached to this matchup were taken from a variety of subjects, apertures, and distances. The undetectable differences between the two hints that perhaps the Pentax-F 50/1.7 inherited its optical identity from the SMC Takumar 55/2.


This matchup panned out the way I would have expected my 8th- and 9th-most used normal lenses to pan out. Optically, I would use these two lenses interchangeably. For this reason, some of the sample images found here are posted full-size, without any sharpening or other post-processing applied.

The extra half-stop of light for the Pentax-F 50/1.7 isn't a tremendous difference. The build of the SMC Takumar 55/2 is arguably better (and not as ugly) but even here I personally prefer the Super-Multi-Coated Takumars over the SMC Takumars.

The one deciding factor for me is the additional feature compatibility of the F-series. Even for adept M42 users, there are still occasions where having full electronic controls is manifestly easier, if perhaps a tad less nostalgic. And of course, for all the auto-focus users there is an obvious advantage. For the automation alone, the winner of this matchup is the SMC Pentax-F 1:1.7 50mm lens.

For the price conscious, the SMC Takumar 1:2 55mm can be found often and cheaply. Mine came for free as an attachment to an M42 adapter that I purchased. The SMC Pentax-F 1:1.7 50mm is usually much more expensive, although good buys like my recent purchase for $40 can still be found.

I have a sample gallery of the SMC Pentax-F 1:1.7 50mm here.

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Sample Images
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