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Pentax Lens Review Database » Film Era Pentax K-Mount Lenses » M Zoom Lenses
SMC Pentax-M 40-80mm F2.8-4 Review RSS Feed

SMC Pentax-M 40-80mm F2.8-4

Reviews Views Date of last review
21 131,749 Wed January 18, 2023
Recommended By Average Price Average User Rating
81% of reviewers $44.75 7.33
SMC Pentax-M 40-80mm F2.8-4

SMC Pentax-M 40-80mm F2.8-4
SMC Pentax-M 40-80mm F2.8-4
SMC Pentax-M 40-80mm F2.8-4
SMC Pentax-M 40-80mm F2.8-4


The M-series 40-80mm has a unique focal length range among all Pentax zooms.  It offers a macro mode at 80mm.

User dkpentax has discovered that there are two variants of this lens. The older variant has felt liner at the rear, see the image above. Also, a dedicated metal lens hood was available.

SMC Pentax-M 40-80mm F2.8-4
©, sharable with attribution
Image Format
Full-frame / 35mm film
Lens Mount
Pentax K
Aperture Ring
Yes (no A setting)
Automatic, 7 blades
7 elements, 7 groups
Mount Variant
Check camera compatibility
Max. Aperture
Min. Aperture
Min. Focus
120 cm
Max. Magnification
Filter Size
49 mm
Internal Focus
Field of View (Diag. / Horiz.)

APS-C: 40-20 ° / 33-17 °
Full frame: 57-30 ° / 48-25 °
Dedicated metal hood or RH-R49
Dedicated hard case
Lens Cap
Plastic clip-on
Weather Sealing
Other Features
Diam x Length
66 x 76 mm
395 g
Production Years
1980 to 1984
Engraved Name
smc PENTAX-M ZOOM 1:2.8-4 40-80mm
Product Code
User reviews
Macro setting at the long end

Two variants. The older variant has felt lining at the lens mount

Manual FocusAperture RingFull-Frame SupportDiscontinued
Price History:

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Sort Reviews by: Date | Author | Rating | Recommendation | Likes (Descending) Showing Reviews 16-21 of 21
Forum Member

Registered: April, 2008
Location: Higham Ferrers, Northamptonshire, UK.
Posts: 62

1 user found this helpful
Review Date: October 9, 2010 Recommended | Price: $10.00 | Rating: 6 

Pros: Chunky well-built lens. Nice bokeh. Cheap.
Cons: Macro focusing iffy. Purple fringing when wide open.

These are very cheap on e-bay. They are quirky and work best from f4 to f16. Not the best Pentax lens. As others have said recognise its limits.
Site Supporter

Registered: February, 2010
Location: Salt Lake City, UT
Posts: 1,892
Review Date: August 16, 2010 Recommended | Price: $20.00 | Rating: 5 

Pros: Cheap, solid build, macro focusing, a cheap way to try out 2.8 glass
Cons: purple fringing on everything

I really expected this lens to perform better wide open than it did. If you use it in moderate light conditions, it works out ok, but keep it away from bright light sources or you'll need to stop down substantially.

The focus on this lens is nicely dampened, the macro focusing by pulling the lens out is budget, but functional.

The color rendition wasn't what I've come to expect from Pentax gear.

Overall this lens is ok. I got it as part of a deal with a bunch of other lenses. If you're looking for inexpensive gear, it's not a bad option, but you'll have to play with it to learn its limitations.
Veteran Member

Registered: June, 2007
Location: Singapore
Posts: 348

2 users found this helpful
Review Date: December 19, 2009 Recommended | Price: $30.00 | Rating: 8 

Pros: rendering, sharpness, unique character
Cons: purple fringing wide open

This is not a very common, non very well loved lens. I had the chance to pick one up at a good price, and took it for a test run today.

It has its own piccadilos, and handles very differently from modern zoom lenses or other M series primes - the focusing ring is the typical well built M series type, but the zoom ring is plasticky in comparison. The 'macro' ability is a nice touch, though the push pull design is no longer common in modern lenses.

The lens does suffer from purple fringing wide open for white surfaces. I tested this against a F 35 - 70 / 3.5 - 4.5, and my sense is that M 40 - 80 is sharper wide open.

All in, its a lens with its own personality - I like it.

Lastly, a picture from it - straight from the camera:

(Non working link removed)
Veteran Member

Registered: November, 2008
Location: The Untied States
Posts: 1,881

1 user found this helpful
Review Date: December 9, 2009 Not Recommended | Price: $40.00 | Rating: 3 

Pros: Appealing aperture range; classic M build
Cons: Awful IQ wide open or close to; poor zoom range; bulky; useless macro feature

This lens has really poor image quality, and nothing else can save it from that. It has a decent build even though two large rings is kludgy and not classically M-styled. But it is soft wide open, and at f/4, and at f/5.6. It really only gets good at f/8 and above, and why on earth would you buy an f/2.8-4 lens to use at f/8? Tons of coma and CA, poor colour reproduction, you name it. The "macro" range is just more of the same, and you can't get much closer with it.

Being just a 2x zoom starting at 40mm is a strange focal range as well. When I had it, I couldn't find any times where I would theoretically want to use it over, say, a 28-80 or a 50-135. The "small" size did not sway me in any situation. And that is not even taking into account the awful image quality.

Save yourself the "experience" and try out a different M lens, and not this one. This lens is one of the few "junkers" Pentax ever produced.
New Member

Registered: May, 2009
Location: UK
Posts: 4
Review Date: July 1, 2009 Not Recommended | Price: $82.00 | Rating: 6 

Pros: Macro, relatively sharp when stop down.
Cons: Useless when wide open.

After owning a few M series and takumar prime lenses, I thought it's time to invest some manual zoom lens. However, this lens is extremely soft with severe CA when wide open. I rather stick to my DA kit lens. Will take it back to the shop and swap for a K24 f2.8 today.
Senior Member

Registered: March, 2009
Location: Gouda, Netherlands
Posts: 165
Review Date: March 12, 2009 Recommended | Price: $20.00 | Rating: 8 

Pros: Cheap, heavy, macro
Cons: zoom is a little bit tough

This lens is a very good lens for the money. OK, it's MF and everything is manual. First I used it a lot because I didn't have more tele. The bokeh is realy great! Look at this: (Non working link removed) and this: (Non working link removed)

Also a little bit more light than other lenses.

The macro is only on 80mm and 1:3. So it's close-up. You have to slide the lens down to get the macro.
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