SMC Pentax-M 100mm 𝒇4 Macro Lens Review

SMC Pentax-M 100mm 𝒇4-32 is an affordable (near) macro lens with 0.5x max magnification that can be converted to 1:1 with extension tubes or used as a telephoto glass.

I tested it in both scenarios for this review, in which it performed very well. But my favourite thing about this lens is the build quality, especially compared to the kit SMC Pentax 50mm 𝒇1.7.

In this review: Specifications. Lens in use: ergonomics. Build quality. Macro image quality. Telephoto image quality. Mounting on digital cameras. Where to buy your Support this blog & get premium features with GOLD memberships!

Specifications.

The SMC Pentax-M 100mm 𝒇4-32 Macro is a manual lens for Pentax K mounts, manufactured between 1977 and 1984. It has five elements in three groups and six aperture blades. It uses a 49mm filter thread. This lens has a 24° angle of view on a full frame.

It has a minimum focus distance of 45cm/18” and a maximum magnification of 0.5x, which can be enhanced to 1x with extension tubes.

This lens is 64.6mm × 77.5mm (2.5” × 3”) and weighs 355g (12.5oz).

Lens in use: ergonomics.

The 100mm 𝒇4 has an enormous focus ring with medium resistance and a near-360° throw. When fully extended for close-up shots, this lens doubles in length to 13cm (5.1”). But for most focus distances up to one metre or three feet, it’s just 45° of throw, which is on par with most lenses.

This lens fits many helpful indicators on the barrel, including the set distance in meters on the tip end. You can see the distance set to about 10m in the photo above, where a white number 10 lines up with the long vertical light that stretches across the inner tube.

Near the base, the distances are indicated in both feet and metres alongside a depth of field calculator. There’s also a tiny red line slightly to the left of the DOF mark for focusing with infrared film. Immediately below that is the aperture ring, which is much thinner but still easy to grip.

I appreciate the middle ring with gripping grooves between the aperture and focus sections, which is fixed to the lens. It’s very helpful for mounting and dismounting the lens without touching the aperture or focus rings. Smaller lenses can throw all the settings out of whack when exchanged, which is not an issue with this one.

As you’d imagine, this lens will not let you pocket your SLR, no matter how large your pocket is. But it’s not so large or heavy that it would tip the tripod, even if the tripod is tiny and the lens is fully extended. There’s nothing you’ll need to learn or do special with this lens unless you plan to use extension tubes (the link takes you to a dedicated guide).

Build quality.

I got my Pentax K100 with the kit SMC Pentax-A 𝒇1.7 50mm lens. I never liked it. While sharp and capable of producing nice images, it was poorly made and felt as if it was falling apart in my hands. This cast doubts in my mind on the build quality of the entire lens lineup for the camera — but thankfully, this 100mm 𝒇4 dispelled those feelings quickly.

The SMC Pentax-M 100mm 𝒇4 Macro features a high-quality build, with the majority of its components being metal and a great overall feel. It’s hefty but not overbearing, and it feels like it can easily last another hundred years. Despite its age, the lubricants still function perfectly and the only thing that can possibly reveal this lens’ true age is that it does not have autofocus.

Macro image quality.

I bought this lens primarily to take product photos and macro shots of cannabis for my article about developing film in weed. It absolutely did not disappoint.

Every shot is exceptionally sharp and free of any aberrations that I could notice when taken at the closest focus distance. Mounting extension tubes did not diminish image quality in any way, which isn’t always a given. Of course, being an 𝒇4 lens, the light transmission is pretty low on this lens, and it becomes even less with the tubes. Thus, I had to use a tripod in all situations except when the object was in full sun (like the one above).

There are other Pentax K-mount macro lenses out there, but I would only consider one with a 1:1 magnification factor (thus, not requiring extension tubes) over this one.

Telephoto image quality.

The SMC Pentax-M 100mm Macro excels as a telephoto lens as well. When used at infinity, it is sharp even when shot wide open without noticeable aberrations or softness in the corners.

The only way I think this lens can be improved, aside from producing 1:1 maximum magnification, is to render more contrast. This isn’t difficult to correct in post or after scanning film, but getting a perfect image out of the gate would be nice.

Mounting on digital cameras.

Any camera that can take Pentax-K mount lenses will work with SMC Pentax-M 100mm. Adapters can make it work with L39/LTM, M39, M42, Nikon AI/AIS, Four Thirds (Olympus), Micro Four Thirds (Olympus and Panasonic), Canon EF-mount (EOS), Minolta/Sony A-mount (Sony Alpha), Samsung NX-mount, Sony E-mount (NEX), and Fujifilm X-mount.

Where to buy your SMC Pentax-M 100mm 𝒇4 Macro lens.

The SMC Pentax-M 100mm lenses aren’t particularly rare, but you need to pick the right one: not the plasticky autofocus versions — the actual vintage 100mm lens. The link below should guide you to the right place.

SMC Pentax-M 100mm lenses are currently listed for $50-200. See this guide if this is your first time buying vintage camera equipment.

❤ By the way: Please consider making your SMC Pentax-M 100mm 𝒇4-32 Macro lens purchase using this link so that this website may get a small percentage of that sale — at no extra charge for you — thanks!