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SMC Pentax-M 40mm F2.8

Reviews Views Date of last review
38 156,497 Fri December 6, 2019
Recommended By Average Price Average User Rating
79% of reviewers $94.15 7.86
SMC Pentax-M 40mm F2.8

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

Also known as the "pancake," this is the smallest SLR lens that Pentax ever produced. It includes all the features of any other M lens.

In 2006, it was superseded by an even smaller DA version, but that version did not feature an aperture ring.

SMC Pentax-M 40mm F2.8
©, sharable with attribution
Image Format
Full-frame / 35mm film
Lens Mount
Pentax K
Aperture Ring
Yes (no A setting)
Automatic, 5 blades
5 elements, 4 groups
Mount Variant
Check camera compatibility
Max. Aperture
Min. Aperture
Min. Focus
60 cm
Max. Magnification
Filter Size
49 mm
Internal Focus
Field of View (Diag. / Horiz.)

APS-C: 39 ° / 33 °
Full frame: 57 ° / 48 °
Hard case HA-90B
Lens Cap
Plastic clip-on
Weather Sealing
Other Features
Diam x Length
63 x 18 mm
110 g
Production Years
1976 to 1984
Engraved Name
smc PENTAX-M 1:2.8 40mm
Product Code
User reviews
Lens was sold without hood. The folding rubber hood RH-A49 fits
Manual FocusAperture RingFull-Frame SupportDiscontinued
Price History:

Add Review of SMC Pentax-M 40mm F2.8
Sort Reviews by: Date | Author | Rating | Recommendation | Likes (Descending) Showing Reviews 1-15 of 38
New Member

Registered: December, 2013
Posts: 11
Lens Review Date: November 28, 2015 I can recommend this lens: No | Price: N/A | Rating: N/A 


I've owed my MX from new when it first came out and still going strong. It came with the standard f 1.7 50mm. Some years ago I purchased a f1.4 50mm , although excellent , it made the camera front heavy and unbalanced. Recently I began to use again an old f2 I had neglected .[All the above are manual SMC.] I find the f2 excellent in terms of lightness and compactness and seems to suit the design of the camera body . This lens I think is a better alternative to the pancake.I remember when the pancake came out I was warned off it by my camera shop . Now it seems popular. Times change. As an aside , I purchased the MX as a first SLR because of it's very compactness being used to rangefinder cameras all the hitherto SLRs , FTb , Nikon F2 , were monsters to me . [ Small hands.] And so the pancake attracted me but I was persuaded instead to buy the F2 . Quite right I think looking back.
Forum Member

Registered: August, 2012
Posts: 51
Lens Review Date: April 7, 2013 I can recommend this lens: No | Price: N/A | Rating: 7 

Pros: Small, well built
Cons: Mediocre optically, very small focusing ring
Sharpness: 7    Aberrations: 8    Bokeh: 8    Handling: 5    Value: 6    Camera Used: LX, ME Super, *ist DL, K-01   

This lens has only one claim to fame - its size. The downside of this was that the focusing ring is very narrow. Optically it is not stellar although good enough for most purposes, especially when shooting film. I used it a bit back in the film days but it never was one of my most used lenses, I mainly used it when I wanted a compact package. The ME Super with this lens was as compact as you could get with a film SLR. The focal length makes more sense on film than on APS-c digital cameras.
Junior Member

Registered: November, 2012
Location: Cosenza
Posts: 42

1 user found this helpful
Lens Review Date: November 11, 2012 I can recommend this lens: No | Price: $90.00 | Rating: 6 

Pros: compact, nice tonality in b/w
Cons: not too sharp
Sharpness: 6    Bokeh: 8    Handling: 8    Value: 6    Camera Used: Canon Eos 5D Mark II, Pentax ME Super   

I had it for a year or so (I love the 40mm focal length), as it made a really nice and compact package on my 5d mk II and, better still, on the ME Super. But I ended up selling it. It has two flaws:

1st flaw (this one only for Canon users)
To use it on a full frame camera you need to remove (better, less messy) or file down the rear fin that commands the aperture, otherwise it will hit the mirror, and badly. I seems to recall that someone ended up with a lens jammed on the camera, too, from what I read elsewhere.

Once removed the fin there is not a problem whatsoever. From what I understand there are no problems in using it on a 1.6x camera, even unmodified (but I didn't try).

2nd flaw
It is a good lens, just not exceptional. And given that you can buy, for a tenth of its money, a Pentax 50mm f/1,7 that not only will be almost the same weight and size but it will be faster, and probably will beat it to death, this pancake it's not a smart buy.

Please, though, take this with a grain of salt: my copy had the focus ring jammed after the previous owner let it fall, and I was able to repair it in a crude but effective way. So maybe my sample was in desperate need of a collimation . But what I read about his lack of sharpness mirrors my own experience with it.
Senior Member

Registered: September, 2008
Location: Norway
Posts: 127
Lens Review Date: September 17, 2008 I can recommend this lens: No | Price: $70.00 | Rating: 5 

Pros: very small, good build quality, fun ?
Cons: could be sharper

The original pancake is a classic. Once again it seems like I did a good buy. It was bundled with a couple of other lenses, but if I split it up it was somewhere around $70 for this one.

It's a bit fun to use, and I don't have a problem with focusing. The focus ring is small, but well defined for you fingertips. To me it feels like it very quickly gets into hyperfocal range. Build quality seems good with metallic construction like other m-lenses.

It really looks sexy on my MG film camera - they are a great pair. However I don't think it is quite as good as a lot of the other m-lenses on a modern digital SLR. I have used it on a K100D, and produced a couple of nice pictures in the golden hour with results a bit like a typical 70s photographic wallpaper

It's fun and easy to find for sale, but don't put too much work into getting one. It feels a bit harsh to say that I don't recommend it. It's not bad, but unless you want it for it's small size, there are probably better lenses out there to spend your money on.
Senior Member

Registered: January, 2008
Location: Bondi, Australia
Posts: 206
Lens Review Date: January 29, 2008 I can recommend this lens: No | Price: $70.00 | Rating: 4 

Pros: small, good optically stoppeddown a bit
Cons: hard to use focus ring

Like nearly all Pentax lenses, it is soft wide open and hits its straps down 2 stops. I found it very hard to use the focusing ring - too small. Quite credible optically, good replacement of a 50mm as a standard lens for those that like it a bit wider. Have a 35 f/2 , so sold off the 40mm while it stil had its cult status. The cult status is probably only for the extreme compactness. In general, I have found the M lenses to be not as good as the K lenses optically.
Veteran Member

Registered: November, 2006
Location: Belgrade
Posts: 656

1 user found this helpful
Lens Review Date: December 26, 2007 I can recommend this lens: No | Price: $140.00 | Rating: 6 

Pros: Small, excellent focal length on film, good for MX/ME/ME Super
Cons: Low corner sharpness below f/5.6 (see the review)
Sharpness: 7    Aberrations: 7    Bokeh: 7    Handling: 4    Value: 5   

I mostly agree with previous comments: the lens is overrated and price should not go over $100 in my opinion.

The major negative aspect is that M40/2.8 does not reach very good corner sharpness until f/5.6 (tested with *istDS) but it is not bad either. Note that center sharpness is good to excellent at all apertures, while I would rate corner optical performance as average at apertures below f/5.6. At f/5.6 corner sharpness improves drastically and the lens performs very well over the range f/5.6-f/16 on both DSLR and film SLR (tested with Pentax MX and ILFORD XP2 film).

However, I would not recommend this lens for use with DSLRs. If you are looking for a compact DSLR lens consider DA40/2.8 Limited. My main reason for getting M40/2.8 is to use it with MX if I decide to shoot a roll of film without carrying my other M lenses: 40mm is very convenient "universal" focal length on film, the lens itself is much smaller and lighter than M50/1.4, and performs very well stopped down which is not a problem at all if shooting in normal daylight conditions (I keep it at f/8 most of the time).
Veteran Member

Registered: September, 2006
Location: Toronto
Posts: 960
Lens Review Date: February 7, 2007 I can recommend this lens: No | Price: $250.00 | Rating: 5 

Pros: small size, light
Cons: difficult to focus, so-so image quality

I bought my 40mm pancake lens with a (very) used MX body. I find it a good combination for street photography, as they make a lightweight combination and the 40mm size is just right for the sort of urban shots I like.

I have also used it on my *istDS body since I added the DSLR to my collection, where its 60mm-equivalent field of view puts it into the far end of 'normal'.

That said, I use this lens less and less with time.

For one thing, the focusing ring is quite difficult to use, as it is very thin. I've found myself with my finger on the ring and my thumb on the aperture ring as often as not. Also, the lens is so short that on the *istDS body the focusing ring is actually tucked under the flash cowling, further jamming things up.

My second reason for ignoring this lens is that it seems to drain a bit of the life from my shots. I don't get the colour or contrast I expect, either in film or digital. Sharpness is not an issue, but I've been disappointed with shots from this lens on a few occasions.

Ouch. What can I say, I live in Tokyo.

If you're looking for a small and light street photography combination for digital, get a point-and-shoot. For film, I recommend an old rangefinder. No TTL, it's true, but they're tiny and kinda fun.

edit [2007/03/26]
I sold this lens, as I was no longer using it. I've bumped it down a notch to a '5', as well, because this is nowhere close to the SMC 28mm lens I use as my 'normal', and I only gave that one a '7'. 8)
Veteran Member

Registered: September, 2006
Location: North Idaho
Posts: 665

1 user found this helpful
Lens Review Date: January 9, 2007 I can recommend this lens: No | Price: $100.00 | Rating: 5 

Pros: small, exceptional construction quality
Cons: difficult ot find focus ring when used to 'normal' sized lenses

The SMC Pentax-M f/1:2.8 40mm is the original Pentax "pancake" lens. At the time, it was the only one produced (by Pentax) and was highly desirable for the M bodies. The combination made it the first "pocketable" SLR camera. (But, you needed a large pocket.)

The construction quality is typical of K and M series lenses. All metal and glass. No plastic here! Optically, it was not anywhere as good as the 50/1.4 or 50/1.7 lenses. Probably on par with the 50/2.0 lens. The lens attained 'cult' status and was desirable only because of its size, not because of its optical qualities.

Only rated at 5 because of the fair optical quality. Given a 'no' recommendation because of the price/performance ratio. Today, you should only purchase this lens for the 'collector value', and only if you have a MX or ME body to mate with it. The DA40/2.8 is a much better lens if you want to actually take pictures. This lens still sells for a premium price on the used market, and in my opinion, not worth the cost! It is an "okay" lens, just not worth the premium prices asked and paid.
New Member

Registered: February, 2012
Posts: 15
Lens Review Date: December 6, 2019 I can recommend this lens: Yes | Price: $25.00 | Rating: 9 

Pros: Very sharp from f5.6 onwards, good colours, super-compact, good standard lens of APS-C
Cons: Ntot great at f2.8 so hard to judge manual focus, flare can be a problem
Sharpness: 9    Aberrations: 9    Bokeh: 9    Handling: 8    Value: 10    Camera Used: GX10, GX20, Kx   

I paid 19 for this online; don't ask me why it was so inexpensive.

It is very compact. It's not very good at f2.8, and this makes precise manual focusing tricky, but it is pretty much as sharp as the Pentax 50mm offerings across the APS-C frame when stopped down to f8 and f11.

The bokeh is inobtrusive.

The colours are great.

The minimum focus is 60mm, so not great, but sufficient for an arms length selfie.

It isn't weatherproof, but it is so small it is partially shielded from the elements by the DSLR bodies, and I have confidence it is as rugged as they are.

40mm on an APS-C is equivalent to about 60mm on full frame, so it's very similar to using the Helios/BIOTAR 58mm on a 35mm camera. I prefer the perspective of the 40mm to the 35mm.

I use it, a lot, when hiking, skiing, dog-sledding; any activity where I want to take my camera, but I want to minimise weight and it might be exposed to physical abuse. For views, I can just set it to infinity and f11 and they turn out well.

Unless you are actively seeking veiling flare, do not include the sun in your frame!

I like to boost the contrast out of the camera, but it's a matter of taste. As others have noted, the images from this lens are quite distinctive.

Well worth my rating of 9, I reckon.
Forum Member

Registered: November, 2018
Posts: 95

1 user found this helpful
Lens Review Date: October 3, 2019 I can recommend this lens: Yes | Price: N/A | Rating: N/A 


Junior Member

Registered: September, 2014
Location: United States
Posts: 35

1 user found this helpful
Lens Review Date: January 29, 2019 I can recommend this lens: Yes | Price: $95.00 | Rating: 7 

Pros: Super-Slim, great walk-around lens
Cons: focusing is a bit difficult due to size, okay bokeh, min. focus distance
Sharpness: 7    Aberrations: 7    Bokeh: 5    Handling: 7    Value: 8    Camera Used: Sony A7   

Got this lens with a bit of balsam separation. Fixed it and functions well. profile is super slim even with an adapter for the A7. It is a great walk-around lens, but other than that, you wont have too much creative license with it. The most disappointing aspect is the quite long min. distance focus. Other than that, I think it's worth the money, especially if you just want a lens to tack on and head out the door.
PEG Moderator

Registered: August, 2008
Location: Hielands o' Scootlund
Posts: 45,110

1 user found this helpful
Lens Review Date: September 12, 2018 I can recommend this lens: Yes | Price: $90.00 | Rating: 8 

Pros: She's wee
Cons: Green button use for exposure
Sharpness: 8    Aberrations: 8    Bokeh: 6    Handling: 6    Value: 9    Camera Used: K1   

Just purchased today on a wee whim, as she looked like an inexpensive bit of fun.

Planned to use as a more discrete "Street" lens, but married it up with Takumar 35mm rectangular hood, which is nearly twice as long (deep) as the lens.

Had her oot and aboot with me today, no initial problems apart from a little tricky to use as she is so wee, but got the hang of her now with Hyperfocal Focusing.

Forum Member

Registered: February, 2016
Location: Moab, Utah
Posts: 90

1 user found this helpful
Lens Review Date: January 15, 2018 I can recommend this lens: Yes | Price: $140.00 | Rating: 10 

Sharpness: 7    Aberrations: 9    Bokeh: 7    Handling: 10    Value: 10    Camera Used: Sony A7s, A7ii   

This lens is incredible and unique. One of my favorite Pentax-M lenses. I use it on full frame bodies. It's not razor sharp like the M 50 f2 until about between 4 and 5.6 (at which point it is very sharp.) However, it has more pop than the smc Takumar 35 3.5 in my opinion. I did a side by side comparison in overcast low light. In bright light, it flares extremely easily, and that is it's weakness/character along with some minor vignetting. This lens has a unique glow about it. It's known for being a street photographer's lens, but I think it's more than that. It's just a great lens. I like it so much, I think it's one of the 5 best M series lenses, and also represents the M series really well being the smallest "Pentax" lens up until the DA. This lens is slightly larger than the fisheye takumar 18mm 1:11 though. I have a video talking about this lens with example images for anyone interested:
New Member

Registered: October, 2011
Posts: 9
Lens Review Date: March 31, 2017 I can recommend this lens: Yes | Price: $70.00 | Rating: 9 

Pros: Small, solid, easy to use, fun, interesting results, great for close up photography.
Cons: Not so good for landscapes
Sharpness: 9    Aberrations: 8    Bokeh: 7    Handling: 10    Value: 10    Camera Used: K5   

Interesting little lens. I can see why some people give it negative reviews. For landscapes on an over cast day it is pretty crap. I am presuming this is because of it's design (I could be wrong) which seems to give it an abnormal shallow depth of field. The first pictures I took were on a very grey day and appear somewhat all soft. However, when photographing close ups, it is tack sharp and has wonderful contrast and colour. As you can see below, the station shot is a bit dreary and soft at the edges whilst the flowers are sharp but have a quick fall off and the bug hotel holds focus all over the frame. I was only messing with it in the sun this morning so I'm not posting award winning pics, but I hope you agree, the latter three pictures do have a lot of charm.

New Member

Registered: February, 2013
Posts: 20
Lens Review Date: December 29, 2016 I can recommend this lens: Yes | Price: N/A | Rating: 8 

Pros: size, size, size :)
Cons: 5-bladed iris ain't ideal (but better than 6)
Sharpness: 8    Aberrations: 8    Bokeh: 7    Handling: 7    Value: 7    Camera Used: Pentax MX, Fuji X-M1   

Nifty little lens which just got a new lease of life on my Fuji X-M1, just look/click at the following picture why:

Plenty sharp from F5.6, impeccable coatings (what else would you expect from Pentax), handling is a bit challenging because of it's size, but this lens IS about size...
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