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SMC Pentax-M 120mm F2.8

Reviews Views Date of last review
11 65,411 Fri September 4, 2020
Recommended By Average Price Average User Rating
100% of reviewers $115.00 8.90
SMC Pentax-M 120mm F2.8

SMC Pentax-M 120mm F2.8
SMC Pentax-M 120mm F2.8

The M 120mm F2.8 is a fast telephoto lens that's lighter than its K-series predecessor.

SMC Pentax-M 120mm F2.8
©, sharable with attribution
Image Format
Full-frame / 35mm film
Lens Mount
Pentax K
Aperture Ring
Yes (no A setting)
Automatic, 8 blades
5 elements, 5 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: 14 ° / 11 °
Full frame: 20 ° / 17 °
Built-in, slide out
Dedicated hard case
Lens Cap
Weather Sealing
Other Features
Diam x Length
63 x 63 mm
270 g
Production Years
1977 to 1985
Engraved Name
smc PENTAX-M 1:2.8 120mm
Product Code
User reviews
Manual FocusBuilt-in HoodAperture RingFull-Frame SupportDiscontinued
Price History:

Add Review of SMC Pentax-M 120mm F2.8
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Forum Member

Registered: July, 2020
Posts: 92

2 users found this helpful
Lens Review Date: September 4, 2020 I can recommend this lens: Yes | Price: $165.00 | Rating: 10 

Pros: excellent optics; f/2.8; relatively small and light; good build; retractable lens hood
Sharpness: 9    Aberrations: 9    Bokeh: 9    Handling: 10    Value: 10    Camera Used: LX, PZ-1, K10D, K-3 II   

I bought this lens for fairly cheap but in mint condition at a camera show many years ago (ca. 2000) -- not sure what I paid, but likely around $100 (though there is "165-" written on a label on the rear lens cap, so I may have paid that). It's a great piece of glass, with the usual good focusing ring that makes it very easy to get sharp focus in the old M lenses. The thickness of the focusing ring is about 40% of the length of the lens barrel, and it turns counter-clockwise (as seen from the back of the camera) about 250 degrees (or about 2/3 of a full turn) in going from infinity to the shortest focus, allowing very fine focusing. The filter does not rotate when focusing. I've used this for astrophotography a fair bit, both with and without the Pentax Rear Converter-A 2X-S, and the sharpness is quite good with the 2X converter using a clock drive for longer exposures. I've also tested with an Edmunds resolution test chart. I tend to stop down to about 5.6 for my astronomy shots, but I've done shots wide open at f/2.8 (and at 240mm f/5.6 with the 2X converter) and see no real degradation. The aperture ring is set back a bit from the camera mount, and its 360-degree ring allows easy movement of the aperture ring from all sides of the camera.

The built-in hood is one of the great designs of the older Pentax telephoto lenses, and it's really useful in this lens as in all the larger Pentax lenses that I have with this feature. This is a nice lens to carry along on trips and hikes as a second or third lens because it takes up so little space. Highly recommended if you get a mint copy for cheap.

photos with the lens on my camera showing the hood extended and retracted:


Registered: April, 2009
Location: Madrid, Spain
Posts: 7,515

2 users found this helpful
Lens Review Date: September 1, 2020 I can recommend this lens: Yes | Price: $130.00 | Rating: 8 

Pros: Typical M series build quality, sharp with good contrast and colour
Cons: Could be sharper wide open
Sharpness: 9    Aberrations: 9    Bokeh: 8    Handling: 9    Value: 8    Camera Used: K-3   

I have owned this lens for a few years and am adding a review as there aren't many and I feel that this lens is under-rated, though I'll admit to not knowing it's ins and outs as well as I do with many of my other lenses.

I bought this lens mainly to use as a mid-telephoto on my APS-C DSLRs for travel. I had previously used the M 135/3.5 for that purpose but it was a bit too long and needed to be stopped down a couple of clicks to get decent sharpness. The DA 55-300 is too big and heavy and the DA 50-200 is just not good enough optically, especially with regard to sharpness, and is too slow.

In it's role as travel telephoto the lens has been with me to Japan, Italy and to the Spanish coast and has performed well. The focal length on APS-C is ideal, allowing reach but not to the extent that I frequently find I can't fit the whole subject in the frame. Sharpness wide open is acceptable even on the 24MP K-3 sensor and colour and contrast are good, though contrast could be a little better. Stopped down to f/4 and beyond I have absolutely no complaints about the sharpness. The build quality is typical of the M series: solid and compact with smooth focusing and a nice click to the aperture ring. The little pull-out hood, while very short, is handy to have. Overall I definitely prefer the results from this compared to the cheaper consumer zooms and the extra speed is very welcome too for both isolating subjects and getting faster shutter speeds - I prefer speed and IQ over the the flexibility of a zoom. There is a bit of green fringing wide open in high-contrast parts of the image.

As a telephoto lens at a slightly unusual focal length this lens gets compared a lot to the M 85/2, 100/2.8 and 135/3.5. Compared to them it's better than the 100 and 135 (sharper, better contrast) but not the 85mm, which is close to spectacular, but significantly shorter in focal length. It's also rarer than those other lenses, so it might take some time to find one.

I would recommend this lens to anyone looking for a small, fast prime in the focal length. It's very competent without being outstanding.

Some samples below.

by Jonathan MacDonald, on Flickr

by Jonathan MacDonald, on Flickr

by Jonathan MacDonald, on Flickr

by Jonathan MacDonald, on Flickr

by Jonathan MacDonald, on Flickr

Watching and waiting
by Jonathan MacDonald, on Flickr

by Jonathan MacDonald, on Flickr
Inactive Account

Registered: November, 2009
Location: Sofia
Posts: 3

2 users found this helpful
Lens Review Date: July 23, 2013 I can recommend this lens: Yes | Price: $80.00 | Rating: 10 

Pros: Sharp,Colours,build quality, performance,lens hood
Cons: No
Sharpness: 9    Aberrations: 9    Bokeh: 7    Handling: 10    Value: 10    Camera Used: Samsung GX-10   


Registered: February, 2007
Location: Aurora, CO
Posts: 5,867

6 users found this helpful
Lens Review Date: January 21, 2013 I can recommend this lens: Yes | Price: $120.00 | Rating: N/A 

Pros: Size, MFD, f2.8
Cons: no KA mount version

I am a 135mm collector/user/fan and 120mm seemed like splitting hairs. This review will concentrate on comparing the M120/2.8 to the familiar 135mm. Because of that, I didn't rate sharpness, etc. - I can only do that in comparison to 135mm terms (unfair) or the other 120s (only one, that I haven't used).

Here's a quick example of the difference in field of view. I reduced a Pentax-M 135mm f3.5 shot by 88.89% and overlaid it on an M120/2.8 shot:

I had one of the best 135s, the SMC Pentax 135mm f2.5, so I didn't need a 120. I bought one anyway, because it's small. Almost immediately, I sold the big K135/2.5. I had no complaints with its IQ, just its size. Add a hood and it's worse. I rarely traveled with it, limiting its usefulness for me.

Today I've done some boring brick wall and other tests. (I discovered it was falling a bit short of infinity, fixed that.) I have a Pentax-M 135mm f3.5 that was pretty close to my K135/2.5. I was able to verify a few things:
  • The field of view is really close.
  • It really is a half stop faster than the M135/3.5, therefore only a third of a stop slower than the K135/2.5.
  • I can crop the M120/2.8 to the 135 field of view and get just about the same image. The only clue is that wide open, both lenses have some vignetting. I was looking at two shots taken wide open, and had cropped away some of the 120's vignetting. The overlay above was two shots wide open also, you can see it there.
  • Purple fringing is worse on the M135/3.5, even though the 120 is faster. Weird.
  • The out of focus areas still have the same/close color fringing.
  • I'll say bokeh is the same too, but I'm not a great judge of this.
It's tricky to compare different focal lengths, even close ones, but my guess is these lenses are as close as they can be. It's hard to pick up the right one without double-checking. The Pentax-M 120mm f2.8 has some advantages that make it worth your hunt. Shorter minimum focus distance than most 135s, about a foot/300mm/20% less. It's 3mm shorter than the M135/3.5, or two rows of rectangles on the rubber focus grip. It's just over half the weight of a K135/2.5. It has an 8 blade aperture too, an upgrade over the K or Takumar 120s. It has the slide-out hood like other M telephotos.

The Pentax-M 135mm f3.5 is easy to find for $50 or less. The K135/2.5 is not that common and around $200. The Pentax-M 120mm f2.8 should be somewhere above the 100/2.8. I think around $120-150 is fair. The main issue is finding one for sale, which probably means paying more than you want to get the one you see today.
Junior Member

Registered: January, 2013
Location: Texas
Posts: 32

1 user found this helpful
Lens Review Date: January 5, 2013 I can recommend this lens: Yes | Price: N/A | Rating: 9 

Pros: Focal of 120mm, aperture / weight, telescopic hood
Cons: sharpness and contrast only 'good'
Sharpness: 8    Aberrations: 9    Bokeh: 9    Handling: 10    Value: 9    Camera Used: MX, ME Super   

Very good all-round lense. I like the focal of 120mm, uncommon but nice to use. This lense is good at full aperture, but improves only slightly at smaller apertures. I wonder if an increase of contrast using Photoshop would yield.

Registered: March, 2008
Location: Quebec city, Canada
Posts: 8,146
Lens Review Date: October 19, 2012 I can recommend this lens: Yes | Price: $85.00 | Rating: 9 

Pros: Compact, high IQ
Cons: None really
Sharpness: 9    Aberrations: 7    Bokeh: 7    Handling: 9    Value: 9    Camera Used: K20D   

This lens has a slightly oddball, but very comfortable focal length. 120mm is very well suited as a short tele, more so than 135mm in my opinion.

What impressed me the most about this lens is the very compact size it offers for a f2,8 lens. Wider but no longer than the M150 f3,5. Build quality is excellent, like all M lenses. The focus ring is smooth and has a long throw. The Aperture ring clicks well at all positions, without jamming anywhere.

IQ is great, surprisingly low aberrations and good sharpness. The lens is bright enough that manual focus is reasonable easy. However, the images lack the punch of some more recent lenses. They should react well to post-processing, but out of the box, they are more subdued, less saturated than what current Pentax lenses produce.

All in all, this is a great lens without any serious flaw.
Forum Member

Registered: March, 2010
Location: Norfolk
Posts: 84
Lens Review Date: July 25, 2011 I can recommend this lens: Yes | Price: N/A | Rating: 10 

Pros: compact, fast, build quality, performance
Cons: none

This is the best of all Pentax's M-series medium teles, in my opinion. It's light, short-barreled and decently fast at f/2.8, with great IQ and build. I used it entensively on my MX and now, on a dSLR, it becomes a classic 180mm sports tele. I wish they'd revive it in DA Limited form. I often choose the 120mm over my A-series 100mm (good though that is) because the extra reach is achieved without any noticeable increase in bulk, and the slide-out lens hood is deep enough to be effective. Cannot be faulted.
Veteran Member

Registered: September, 2006
Location: Denver, CO
Posts: 10,686

4 users found this helpful
Lens Review Date: April 15, 2011 I can recommend this lens: Yes | Price: $160.00 | Rating: 10 

Pros: much smaller & lighter than any 135/2.8, sharper than most too, with great bokeh; has built-in hood
Cons: contrast may be slightly less than some other lenses

I have owned this lens for just a month , but have done fairly extensive testing against the M100/2.8 and M135/3.5 (as well as DA50-200), and have now used it for several concerts shoots. All on APS-C/digital.

I got this lens to pair with my DA70. Before getting the DA70, I used the M100/2.8, and considered it the best single focal length for my purposes. But of course, no prime can be perfect for all settings. Sometimes 100mm is too long, and sometimes it is too short. After getting the DA70 to handle the cases where the 100mm was too long, I stopped using the M100/2.8 so much, as it felt too close in focal length to the DA70. Instead, I paired the DA70 with the M135/3.5. But 135mm was a bit too long more often than I would like, and while f/3.5 is only a half-stop slower than f/2.8, that can matter in concert photography. So I eventually got the M120/2.8, hoping it would be a better focal length to pair with the DA70.

So far, it is doing exactly what I hoped and then some. The 100 is very sharp at portrait distance but lacks the reach needed to resolve much detail in more distant subjects. The 135 has the reach to resolve detail in distant subjects but is noticeably less sharp than the 100 in a portrait context. The M120/2.8 manages to be *almost* as good as the 100 at portrait distance, and *almost* as good as the 135 with distant subjects. This makes the 120 a wonderful compromise between the 100 and 135, while also incorporating some the best features of each: the f/2.8 of the 100, the built-in hood of the 135.

Looking past resolution, the M120/2.8 also has much less purple fringing than either the M100/2.8 or M135/3.5 when used in high contrast settings. I'm not a bokeh connoisseur, but I am quite struck by the rendering of the 120 as being noticeably better than 100 or 135, and quite a few people have commented on this in the images I've posted, so I know it's not just me. I do have a sense that the images from the M120/2.8 might be slightly less contrasty than those from the 100, although when I've attempted to compare this specifically, there is very little difference.

Here is the comparison I did with the M100/2.8 and M135/3.5, with plenty of boring test images:

My conclusions from a few posts later in the thread:

The 120 is exactly the compromise between the other two I hoped it would be. More "reach" than the 100 (and with a built in hood); faster, wider, and sharper than the 135 when used indoors at closer range. The fact that it also has the least purple fringing and, for me, perhaps the nicest bokeh, is a bonus, although it does prove to be marginally slower than the 100 (less than a quarter stop). If you're looking for a good general purpose medium telephoto lens for both indoor and outdoor use and fear a 100 would be too short too often and a 135 would be too long too often, the 120 is your lens. Unfortunately, it is much harder to come by than the others. It usually sells for $150-$200, but you may have to wait a while for the chance to buy one.
The bottom line for me is that the M120/2.8 seems to be the best general purpose telephoto prime of the three. And assuming you value small size & light weight, it's probably the best general telephoto prime, period. And of course, there's nothing remotely like it for any other system.

Some sample images:

Forum Member

Registered: April, 2009
Location: Sterling, VA
Posts: 70

1 user found this helpful
Lens Review Date: December 10, 2009 I can recommend this lens: Yes | Price: $25.00 | Rating: 5 

Pros: Light, compact, built-in hood
Cons: optics les than great

This lens is fine for an overall shooter where a mild telephoto is needed, but I would not recommend this as a go to telephoto for protraits. Contrast was average, and the colors were less than I would expect. Still, it has its pluses; light, fairly compact.
New Member

Registered: February, 2009
Location: CA
Posts: 18
Lens Review Date: May 20, 2009 I can recommend this lens: Yes | Price: $180.00 | Rating: 10 

Pros: Sharp, Very compact, fairly bright, nice build, built-in hood
Cons: no

a very good smc-m lens.
compact design with buildin hood.
deliver sharp picutres.

Registered: March, 2007
Location: Greater Copenhagen Area
Posts: 378

1 user found this helpful
Lens Review Date: February 7, 2009 I can recommend this lens: Yes | Price: $90.00 | Rating: 8 

Pros: Very compact, fairly bright, nice build, built-in hood
Cons: M-lens and therefore only M-mode

This is a very nice lens - one of the last in the M-series. It has the same high build quality as the rest of the M-series with a very smooth focusing ring. 8 aperture blades gives a nice out-of-focus rendering.

The image quality is quite comparable to the M 135/3.5 with a somewhat brighter viewfinder and even more compact dimensions. This compactness is perhaps what I like best about this lens.

CA has not been a problem for me with this lens.

Pictured on my K10D:

Size in comparison with DA 16-45:

Some samples:

Handheld F4.5 @ 1/20 sec and iso 200:
Add Review of SMC Pentax-M 120mm F2.8

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