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SMC Pentax-A 100mm F2.8 Macro Review RSS Feed

SMC Pentax-A 100mm F2.8 Macro

Reviews Views Date of last review
5 64,929 Tue March 29, 2011
Recommended By Average Price Average User Rating
100% of reviewers $600.00 9.20
SMC Pentax-A 100mm F2.8 Macro

This was the first Pentax 100mm macro lens to employ an aperture of 2.8 and 1:1 magnification.

SMC Pentax-A 100mm F2.8 Macro
©, sharable with attribution
Image Format
Full-frame / 35mm film
Lens Mount
Pentax K
Aperture Ring
Yes (A setting)
Automatic, 8 blades
7 elements, 7 groups
Mount Variant
Check camera compatibility
Max. Aperture
Min. Aperture
Min. Focus
31 cm
Max. Magnification
Filter Size
58 mm
Internal Focus
Field of View (Diag. / Horiz.)

APS-C: 16 ° / 14 °
Full frame: 24 ° / 20 °
Not needed
Hard case HG-140
Lens Cap
Weather Sealing
Other Features
Diam x Length
74 x 93 mm
470 g
Production Years
1985 to 1989
Engraved Name
smc PENTAX-A MACRO 1:2.8 100mm
Product Code
User reviews
Manual FocusAperture RingAutomatic ApertureFull-Frame SupportDiscontinued
Price History:

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Site Supporter

Registered: January, 2011
Location: The Canadian WetCoast
Posts: 374
Lens Review Date: March 29, 2011 I can recommend this lens: Yes | Price: $700.00 | Rating: 9 

Pros: Fantastic IQ
Cons: "Numb" focusing ring

This lens doesn't come out from my camera bag often during the last couple decades as I reserve it as a true macro and copying lens only. Once it is mounted, and especially with an extension tube for magnification, it open another dimension to my photographic vision.

I have compared this lens IQ with more modern and prestige macro lenses, but hardly notice much difference in terms of sharpness, contrast & saturation. I also notice as previous reviewers pointed out, that it probes to flare more when wide open on a dSLR than on film camera. Although that reason alone is not enough to convince me to get the "new & improved" version.

Major criticism from me is the focusing ring really "numb", which can be hard when focusing manually with magnified subjects even on a tripod.
Senior Member

Registered: May, 2008
Location: Coffs Harbour, Australia
Posts: 298
Lens Review Date: February 22, 2010 I can recommend this lens: Yes | Price: N/A | Rating: 10 

Pros: Amazingly sharp, excellent consruction, smooth focus
Cons: Availability and price

After wanting this lens for some time I finally found it at an estate sale in mint condition for a great price (so low I won't list it to prevent skewing the average). I had refused to pay the over-inflated prices seen online lately. I've used this for insect macro, portraits and light box work, all with outstanding results. This lens is a joy to handle and I prefer it over all similar macro lenses I've tried. This really could have been a star* lens.

If you can find it a reasonable price, don't hesitate.

Registered: February, 2008
Location: Waterloo, Ontario
Posts: 4,462
Lens Review Date: February 19, 2008 I can recommend this lens: Yes | Price: $700.00 | Rating: 9 

Pros: Incredibly sharp and contrasty, fast
Cons: Manual focus but hardly an issue for most macro work, expensive
Sharpness: 10    Aberrations: 10    Bokeh: 9    Handling: 9    Value: 8   

I bought this lens new in the early 1990s. The Pentax A 100mm f 2.8 macro is one fine piece of glass. It has achieved a “legendary” status amongst its users. If incredibly sharp and contrasty images make for a “legendary” lens this one deserves the title. The build quality is absolutely world class in every way. It is a tad on the heavy side (470g.) probably due to its all metal construction and accepts 58mm filters. It is a “true” 1.1 macro lens with a minimum focusing distance of 31 cm. The front element is deeply recessed and as a result no lens hood is needed. Focusing with the A 100/2.8 takes a bit of getting used to. Initially I found it difficult but after prolonged use it is just second nature now.
As DAP notes above this may be "due to the fact that the lens racked out to 1:1 with only one revolution of the focus ring." It can be "finicky" until you get used to it. The rear element protrudes a bit and could be prone to damage if you are not cautious when changing lenses. Some respected forum members (Wheatfield, arpaagent) have noted sensor refelctions when using it wide open on digital. Boz Dimitrov provides further details at

It works very well on both my Pentax K10 digital and MX film camera. It is very versatile and I use it for macro work, as a portrait lens and once in a while for birding.

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If I had one complaint about this lens, at least for film, it would be that it is too short. Longer is always better in macro. I find I have to get too close for some shots. On the digital K10 this is not as big an issue as it performs as a 150mm macro. The added length makes a big difference for lighting setup as does the f 2.8 speed. I would love to have the Pentax A 200mm macro but it is hard to find and who can afford it? It seems we always want what we can't have. For the moment the A 100mm macro more than meets my close up needs. Here's a recent insect shot - handheld on a windy day.


I recently had a chance to compare the A 100 2.8 macro with Pentax's current offering the much lighter D FA 100 2.8 macro. It was a quick and dirty comparison and permitted little more than a chance to evaluate build quality. On this level alone the difference was staggering. The A version featured all metal construction, a 58mm vs 49mm barrel and was much more substantial in every way. The D model was auto focus but seemed to hunt a lot when focusing. It was my impression I could focus at least as well manually. This was a quick first impression of course but I can't see where the auto focus was any improvement at all as far as macro work goes. As a portrait lens the D version's auto focus is welcome and it would be much less weight (345 grams) to carry around. These features don't trump the build quality issue in my mind and I won't be upgrading to the D model for that reason alone. There were just too many plastic bits for my taste. I assume image making abilities would be comparable but I didn't have the time to really check this out. I have watched for the A 100 2.8 macro on EBAY for over a year now and note it seldom makes an appearance. Like myself, those who have a copy are holding on to it.
Senior Member

Registered: February, 2007
Posts: 151
Lens Review Date: May 29, 2007 I can recommend this lens: Yes | Price: $500.00 | Rating: 8 

Pros: Really sharp
Cons: Expensive, focus is touchy and underdamped

Honestly I was kind of disappointed when I got my hands on this lens. After hearing how "legendary" it was I guess I was expecting a bit more. The build is good - all metal and relatively solid. The sharpness and overall image quality was fantastic (I would give it a 10 in this respect), but in no way was it any better than my much cheaper Tokina 90mm macro. I guess my main problem with the lens was the focus "feel" - it was way underdamped (it could be that it was just a problem with my copy) and due to the fact that the lens racked out to 1:1 with only one revolution of the focus ring, it was a bit too finicky for my liking. I sold it shortly after I bought it and haven't missed it in the least.
Inactive Account

Registered: November, 2006
Location: Italy
Posts: 46
Lens Review Date: April 30, 2007 I can recommend this lens: Yes | Price: $500.00 | Rating: 10 

Pros: Outstanding optical quality, magnification 1:1.
Cons: Not AF (not a problem for me).

The best Macro 100mm lens Pentax made.
I have the M100 f/4 Macro and the FA 100mm f/2.8 Macro; no discussion: this is a really outstanding Macro from Pentax, the best 100 ever. Only the FA 50mm f/2.8 Macro it's similar (and obviously the A* 200mm F/4 Macro ED).
A dream.
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