Review: smc Pentax-M Macro 1:4 100mm

The Pentax SMC 4/100 Macro is a small and affordable macro lens from the 70’s. In this review I check if it can still deliver on  today’s 24 Megapixel Sony a7.

Pentax 4/100 Macro Review
Pentax 4/100 Macro

Sample Images

Pentax SMC 4/100 Macro | f/4 f/5.6

Pentax SMC 4/100 Macro | f/8
f/8 cropped quite a lot
Pentax SMC 4/100 Macro | f/8


Diameter 63 mm
Length 56 mm
Filter Diameter 49 mm
Weight 357g
Max. Magnification 0.5
Close Focusing Distance from the sensor 45 cm
Number of aperture blades 6
Elements/ Groups 5/ 3

The Pentax 4/100 Macro at | | (affiliate links)

What is it good for?

Today 100mm Macro lenses are very popular because they are so versatile. You can use them for a very wide many applications ranging from macro over portraits to landscapes.  

The rather slow speed of the Pentax 4/100 limits it’s usefulness as a portrait lens but it is very light and not that big which make it a good choice for a small and versatile tele lens.

Built Quality

The Pentax Macro is built very well, everything is made from metal or glass and markings are engraved.

Both aperture- and focus ring move precisely.  

Size and Weight

The Pentax 4/100 Macro focused at infinity and 45cm

The Pentax 4/100 Macro is of average size, typical for 100mm lenses, my Tokina 2.5/90 Macro and Minolta MC 2.5/100 are similar in size. If you consider that both lenses are more than a stop faster you wonder what Pentax needed all that space for. One ncie aspect is that the front lens is so far recessed that you can throw the lens into your bag without having to worry about getting it scratched. 

he lens is well balanced on the Sony a7 but adding a L-bracket improves the balance further.

Pentax 4/100 Macro Review
Pentax 4/100 on Sony Alpha 7


You have to turn the focus ring clockwise to focus further away, Nikon and Pentax users are used to this focus direction but for me who is used to Minolta SR and Canon FD lenses it was harder than expected to adopt to it.

The focus ring turns about 80 degress from infinity to 1m and a further 250 degress to the dshort focusing distance of 45cm.

This is quite good for macro work but the focus throw is a bit short for portrait and landscape work. The focus ring is harder to turn than I like it, my Tokina 2.5/90 feels much smoother. My copy is in excellent condition so it is unlikely that it is just my copy.

Pentax 4/100 Macro Review
The focusing window

The aperture ring feels very solid and precise.

There are full stops from f/4 to f/5.6 and f/22 to f/32 and half stops in between. The aperture has 6 straight blades which are clearly visible around defocused highlights.

Optical performance

Flare resistance

Typical for a lens of that era the Pentax 4/100 Macro loses contrast if you point it towards a brighter light source.

Pentax 4/100 Macro | f/4 | flare test
Shaded: good contrast
Pentax 4/100 Macro | f/4 | flare test
not shaded: very low contrast


I think bokeh is quite smooth but the hexagonal structure of the aperture is a bit distracting when you stop down.

Pentax 4/100 Macro | f/4
Sony a7 | f/4

Pentax 4/100 Macro | f/8

Sony a7 | f/8


At infinity the performance is quite unremarkable. Pentax_SMC_100mmf4Macro f/4: The center shows very good resolution with lower contrast, towards the corners sharpness drops to okay levels.
f/5.6: Very sharp in the center, sharp in the midframe and corner regions.
f/8: Very sharp across the frame.

f/5.6 vs f/4

At closer distances it is a bit better but I would advise to stop down to f/5.6 to make the contrast reducing spherical aberration go away.



I bought the Pentax 1:4 100 Macro because I was looking  for a small and light weight macro lens because my current macro the Tokina 2.5/90  felt a bit too large and heavy at times and I was looking for a replacement for those times when size and weight are essential.

The Pentax is a solid performer but it didn’t meet all of my expectations. Yes it’s nearly 200g lighter than my Tokina but not any smaller. I could have learned that from the specifications but because several people wrote about how small it is so I didn’t bother. The mechanics are all right but the focus ring is not as nice of that my Tokina and this subtracts from my ecperience.

Optically the Pentax is again a  good performer but neither has it the great bokeh of my Tokina nor can it match it’s  exceptional sharpness and it shows more axial chromatic aberations.

If I consider the rather affordable price of the Pentax I have to conclude that it offers pretty good value.

The only reason my conclusion is a bit negative is that I compared it to the truly exellent Tokina 2.5/90 Macro which bests it in several aspects so the weight reduction isn’t worth the many tradeoffs I would have to accept if I live with.

All in all the Pentax SMC 4/100 Macro is a good lens without any serious weakness and a solid performance for a good price.

You can buy thePentax 4/100 Macro at | | (affiliate links). For tips on how to get a good copy read my article Lens defects and buying advice.

The right adapter to use this lens on a Alpha 7 series camera can be found on| (affiliate links).

Thanks for showing your support buy using one of the above links  🙂

Full resolution samples

Pentax SMC 4/100 Macro | f/5.6 f/5.6 | I think the bokeh is a bit distracting here

Pentax SMC 4/100 Macro | f/8
f/8 | very sharp across the frame at infinity

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I have two hobbies: Photography and photographic gear. Both are related only to a small degree.

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6 thoughts on “Review: smc Pentax-M Macro 1:4 100mm”

  1. Thanks Phillip, that’s another down ;o)
    Like you, I’d love to find a “Tokina” in a lighter body.
    After hoping that the new FE 90mm F2.8 Macro would be it, I was very disappointed when it finally appeared, to find it was so big and heavy. Not a good match with the A7 IMO, despite its great performance.
    I keep coming back to the CV 90/3.5 APO Lanthar, which has been on my wish list for a long time, but now so rare and getting expensive.

    1. yeah, that Tokina is simply too good 😉

      I didn’t like the Minolta MD 4/100 ebcause of it’s stiff focusing ring. So whats left now? Canon FD 4/100?

      The CV 2.5/75 will probably be my next lens, quite small, fast and decent performance from what I have seen. But the better Ca correction and closer focusing distance of the 3.5/90 are tempting as well.

      1. The Tamron SP 90/2.5 has a very good reputation, but I’ve been put off by reports of sensor reflections with the A7.

        1. The Cosina “Plastic-Fantastic” in the link, is very good once stopped down to 8-11, I own one and it never ceases to amaze. Not very good wider….and very plasticky build, though the MF version I own is a lot better build than the AF version

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