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SMC Pentax-A 20mm F2.8 Review RSS Feed

SMC Pentax-A 20mm F2.8

Reviews Views Date of last review
21 134,297 Wed July 1, 2020
Recommended By Average Price Average User Rating
95% of reviewers $425.72 9.05
SMC Pentax-A 20mm F2.8

SMC Pentax-A 20mm F2.8
SMC Pentax-A 20mm F2.8
SMC Pentax-A 20mm F2.8

The SMC Pentax-A 20mm F2.8 lens is faster than the M or K 20mm lenses, and it was succeeded by an FA autofocus version with the same optics formula.

SMC Pentax-A 20mm F2.8
©, sharable with attribution
Image Format
Full-frame / 35mm film
Lens Mount
Pentax K
Aperture Ring
Yes (A setting)
Automatic, 5 blades
10 elements, 9 groups
Mount Variant
Check camera compatibility
Max. Aperture
Min. Aperture
Min. Focus
25 cm
Max. Magnification
Filter Size
67 mm
Internal Focus
Field of View (Diag. / Horiz.)

APS-C: 72 ° / 62 °
Full frame: 94 ° / 84 °
MH-RB 67mm
Hard case HD-100
Lens Cap
Plastic clip-on
Weather Sealing
Other Features
Diam x Length
70 x 43.5 mm
245 g
Production Years
1985 to 2001
Engraved Name
smc PENTAX-A 1:2.8 20mm
Product Code
22870, 22875
User reviews
The lens hood was not included with the lens
Manual FocusAperture RingAutomatic ApertureFull-Frame SupportDiscontinued
Price History:

Add Review of SMC Pentax-A 20mm F2.8
Sort Reviews by: Date | Author | Rating | Recommendation | Likes (Descending) Showing Reviews 1-15 of 21
amateur dirt farmer

Registered: December, 2014
Location: probably out in a field somewhere...
Posts: 28,789

4 users found this helpful
Lens Review Date: July 1, 2020 I can recommend this lens: Yes | Price: $350.00 | Rating: 9 

Pros: color, clarity, sharpness, rendering, quality-feel
Cons: occasional CA
Sharpness: 9    Aberrations: 8    Bokeh: 8    Handling: 10    Value: 9    Camera Used: K-3   

what a phenomenal lens this little package is...

I remember thinking it was either this or a Voigtlander Color-Skopar 20mm f3.5 at the time that the Pentax lens popped up on eBay.... and I cannot imagine that I am missing a single thing with this lens...

there aren't any negatives to this lens, so let's hit the highlights: beautiful colors, amazing clarity, and sharp as razor - I was consistently surprised at how sharp landscapes, street scenes, etc were with the A20/2.8....

even decent bokeh wide open; stop this lens down and you'll get funky penta-bokeh chunks that can be distracting occasionally...

superior build and handling - the lens feels good in your hand as you focus; it's not a bulky lens by any means, but it is of solid heft....

ok, enough of that - let's see some shots:

crossing Main St by Pepperberry Farm, on Flickr

sunset by Pepperberry Farm, on Flickr

lawn chairs, west field by Pepperberry Farm, on Flickr

so you expect this lens to be great in the big, wide shots.... but how about up close?

Tilly in the box by Pepperberry Farm, on Flickr

post and wire by Pepperberry Farm, on Flickr

corn stalks by Pepperberry Farm, on Flickr

in short - if you are in the market for a wide MF lens - put this one on your list to seek out....

the rest of my flickr album for this lens:

Registered: September, 2017
Location: Medellín
Posts: 1,312
Lens Review Date: December 23, 2019 I can recommend this lens: Yes | Price: $430.00 | Rating: 10 

Pros: Five aperture blades, starbursts, build quality, wide auto aperture.
Sharpness: 8    Aberrations: 8    Bokeh: 9    Handling: 10    Value: 10    Camera Used: Film bodies, K-5   

It's a very good WA lens. Make sure your copy has a calibrated aperture (only relevant if you're shooting it in the A position). Since it's an older lens, get it properly CLA'd if anything doesn't run smoothly, or you have inconsistent results shooting in Av mode. Renders nicely even close up and wide open.
Forum Member

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

2 users found this helpful
Lens Review Date: September 14, 2018 I can recommend this lens: Yes | Price: $575.00 | Rating: 10 

Pros: Sharpness, Color rendering, contrast, lack of coma, vignetting
Sharpness: 10    Aberrations: 10    Bokeh: 9    Handling: 10    Value: 10   

Image quality:
The best 20mm from Pentax in my opinion, and one of the best Pentax lenses ever. I tried; Voigtlander 20 3.5, Canon FD 20 2.8, Zeiss Flektogon 20 2.8 and finally the Pentax, which was better than the others. Voigtlander was second best, but wasn't all that sharp and vignetted. Canon had weird coma but otherwise crystal clean. Zeiss was special purpose close focusing version Distagon and lacked the contrast I wanted. I also have the Super Takumar 20 4.5 to compare this to. I prefer the A series for its speed because hte Super Takumar is also very clean and produces good looking images when used with its hood. The A series doesn't flare easily at all and in fact I rarely bring a hood. Regular 67mm lens hoods cause vignetting so I recommend stepping it up a bit with a step up ring.

Handles well and feels good. Not too big, but big enough that you feel like it's got some quality inside.
New Member

Registered: December, 2016
Posts: 1

8 users found this helpful
Lens Review Date: December 21, 2017 I can recommend this lens: Yes | Price: $525.00 | Rating: 10 

Pros: great build and very sharp
Cons: Corner sharpness and some distortion.
Sharpness: 10    Aberrations: 10    Bokeh: 3    Handling: 10    Value: 10    Camera Used: k10D and K-1   

I have this lens for many years, for me it is excellent for the sharpness, for the construction and for the general quality in any photograph
Some comments below I read that it has low contrast, for me this does not make any sense today, a couple of curves in PS and you have all the contrast in the world. for me what counts is the final quality in a processed image and this lens is the boss of the ultra wide angle lens pentax FF ,because the wide angle DA they are not FF and in this they play with advantage.
this lens is the same optic construction as the FA 20mm with the only difference that the A has 5 blades and the FA 6.
This lens is difficult to find, if you find it buy it,is a safe value.

with K-1,EXIF dates in photo

with K-10D

Site Supporter

Registered: October, 2008
Location: Vancouver, Canada
Posts: 7,346

6 users found this helpful
Lens Review Date: September 28, 2015 I can recommend this lens: Yes | Price: $450.00 | Rating: 9 

Pros: Fast, very wide and a great build & handeling lens.
Cons: Corner sharpness and some distortion.
Camera Used: Pentax film bodies (K1000, KM, KX, K2, K2DMD, MX, LX, Super A, P50)   

The A20/2.8 was released in 1985 and remained in production until 2001. It was a direct replacement for the M20/4. The similar Auto focus FA20/2.8 was available along side the A20/2.8 from 1995 onward.

Decent optics and the A20/2.8 is the sharpest from f/4 to f/11. The A20/2.8 is a bit soft in the corners and suffers from some distortion. An “AL” element would have helped with the corner sharpness. However since the 20mm focal length is so wide, this is less of an issue than with narrower lenses.

Focal Length:
On film this is an ultra wide angle lens and is perfect for landscape/street shooting. On APS-C you get the FOV of what the FA31/1.8 is like on film, wide but a bit less useful.

Better built than my newer FA series lenses and on par with my K/M Series lenses.

The A20/2.8 is a nicely sized well balanced lens that is easy to handle. I have no issues manually focusing the A20/2.8 or using the aperture ring. The A20/2.8 also has an excellent distance scale for hyperfocal focus and size wise a great lens to travel with

The A20/2.8 has a very wide 67mm filter ring, so using a regular filter with the hood is not an issue on film. However Pentax warns against using a polarizer as it may cause vignetting. A slim version probably will be OK, but then you can’t use the screw-in lens hood. There are slight flaring issues if shooting toward the sun, even with the lens hood attached.

The A20/2.8 has a dedicated 67mm metal screw-in lens hood named MH-RB67. The A20/2.8 uses the HD-100 hard or the S70-70 soft lens case. The rather large lens hood will not fit in either case.

F/2.8 is pretty fast for an ultra wide angle lens, so no issues here. It and the FA version are the fastest Pentax 20mm lenses.

The A20/2.8 vs my other similar FL ultra wide primes:
I also own the K20/4 and the A20/2.8 is one stop faster with similar optics, so I would give the edge to the A20/2.8. Compared to the K18/3.5, which has slightly better center sharpness but is 2/3 of a stop slower, I would rank them a tie. All three are good lenses on film, but I would pick the A20/2.8 overall to travel with. However the K18/3.5 is still my favorite ultra wide angle lens, since it will vignette with any filter attached, I seldom take it traveling due to the exposed front element.

I really like the A20/2.8 as a ultra wide angle lens when I travel and shoot colour slide film. It’s a nice size and fast for most lighting conditions, overall a great lens!

I bought my A20/2.8 from a Pentax Forum member and paid $600 CDN. It was in excellent + condition and came with the MH-RB67 hood and original box.

Sample shots taken with the A20/2.8. Photos are medium resolution scans from original slides. Both shots were taken in NYC.

Camera: Super A Film: Fuji Provia 100F ISO: 100

Camera: Super A Film: Fuji Provia 100F ISO: 100

Site Supporter

Registered: July, 2011
Location: Fareham, Hampshire
Posts: 492

2 users found this helpful
Lens Review Date: August 31, 2015 I can recommend this lens: Yes | Price: $334.00 | Rating: 9 

Pros: Build, Handling, Max Aperture, Bokeh for a wide angle
Cons: None
Sharpness: 9    Aberrations: 8    Bokeh: 9    Handling: 9    Value: 10    Camera Used: K3 and now K-1   

It's odd how reviews of the same lens vary so much.
This is my review after using this lens for the Pentax Forums Single in August Challenge.

The A20; I am impressed with this one. It's not a new lens for me but it's normally one of a trio with the 18-135 and a 50. This is the first time I've really had to think hard when using it and it's been fun. On APSC at least I find it to be sharp enough from F2.8 to not worry about. I didn't go near the sharpening box in Lightroom all month.
CAs etc not really an issue, there was some PF but only if I tried a shot that would create that issue for any lens. The genuine lens hood is ridiculously priced so I tried a few variations throughout the month. These ranged from step down rings to a rubber hood.
Flare wasn't really a problem unless shooting towards the sun ( but that's what the DA 15 is for - right?).
All in all this is not a focal length I would normally use on its own ( equivalent FOV to 31mm with a 1.54 crop factor) but it has been a good exercise trying to. It's versatile but not quite wide and not quite normal so you have to work for the shot. I will definitely not be parting with this lens, a keeper without a doubt.

The images for this challenge can be found here:

EDIT: It's now June 30 2020. Since the first review I have managed to get hold of the original lens hood and am now using the lens with the K-1.
With the news of the D FA 21mm I thought it only fair to single the A20 on the K-1 as a concentrated work-out.
Once again the lens has performed exceedingly well. It is sharp as needs be from f8 across the frame and, for close up work, f2.8-4 isolates the subject well with pleasing bokeh. Colours are rendered faithfully whether you are in bright sunshine or shooting in the rain.
The lens is simple to use, smooth to focus and the body is a nice size to hold - very close to the FA31 or K24/3.5. Unless I see something really special from the new lens I can see no reason to part with the A20 (- but then it will be a Limited 😊 - both ? &#128514
Whether you use APSC or FF this lens is a very worthy addition to anyones collection of lenses.

Favourite images to demonstrate the above points:

F8 Sunny
Another Anniversary Today by Warren, on Flickr

F8 Sunny, versatility
A Different POV by Warren, on Flickr

F11 Overcast morning
Yachties Haven and History by Warren, on Flickr

F2.8 Bokeh
Racked by Warren, on Flickr

F4 Bokeh
Production Line by Warren, on Flickr

F2.8 Rain, Pointing up at the overcast sky
Keeper Test by Warren, on Flickr

F5 close, in the rain
Marmite & Dylan by Warren, on Flickr

Oh ... and Macro with a 20mm
Switch to Standby by Warren, on Flickr
Veteran Member

Registered: September, 2013
Location: Sydney
Posts: 844

2 users found this helpful
Lens Review Date: May 10, 2015 I can recommend this lens: No | Price: N/A | Rating: 7 

Pros: Good on film
Cons: Very soft, flare is a problem
Sharpness: 6    Aberrations: 6    Bokeh: 8    Handling: 8    Value: 7    Camera Used: K-3, K2   

So I love wide angle lenses, and also have the DA15, K18, DA21, and DA12-24. Of those, the A20 f2.8 is the worst. It's soft wide open, and still soft when stopped down to F8. It flares horribly, and loses contrast/sharpness with ease. Looking over the reviews here, there does seem to be a trend of a decreasing score over time, and that probably reflects the improvements in sensor technology over time. I'd have said that maybe it was just a bad copy that I had (it's mint), but I just sent it for a CLA, and it's still a disappointment.

With a polariser on, it starts to be usable on digital, but the DA21 is in an entirely different league, so you'd be better off with that. On film it improves a little bit, but again, the K18 does everything this does, but with style, a better build quality, and a far superior image quality. I suppose on the plus side it has A contacts, and f2.8. Those are the only plus points I can see.

It's a good lens for a collector, adequate for a film shooter, but distinctly underwhelming on a k-3.
Senior Member

Registered: June, 2011
Location: Rotterdam, Netherlands
Posts: 235

3 users found this helpful
Lens Review Date: July 23, 2014 I can recommend this lens: Yes | Price: $300.00 | Rating: 8 

Pros: solid, sharp, compact
Cons: none
Sharpness: 9    Aberrations: 7    Bokeh: 9    Handling: 8    Value: 9    Camera Used: Pentax K-5   

I bought this lens online from Hong Kong and unfortunately I had to pay a lot of unexpected taxes upon arrival. But this pain was gone fast after using this little gem in the streets. It's now on my camera all the time. It's sharp, quite fast and also very compact. Perfect for street photography (set it to hyper-focal and shoot without having to focus). Example:

(background of this photo here)

My main utility for this lens is street photography, but I have discovered that it's also great for landscape shots. I mostly keep it on F8, resulting in tack sharp images. It might not perform as a 28mm or 24mm, but for a 20mm you can't get much better I guess. Example

(background of this photo here)

I gave a 9 for it's bokeh. One of the things I like of this lens, is that you can get close to your subject (25cm) and actually get a nice bokeh. For a wide angle lens that is. You can't compare its results to a 50mm or more. Anyway, see for example this image I took.

Overall a lovely lens. Unfortunately my copy needs some calibration as the focus indication is all wrong. This is especially cumbersome for infinity. I've not seen any other complains, so I guess it's just me who is unlucky. I can't wait to try to this lens on a FF Pentax (fingers crossed).

Registered: November, 2011
Posts: 4,205

3 users found this helpful
Lens Review Date: August 23, 2013 I can recommend this lens: Yes | Price: $570.00 | Rating: 8 

Pros: Good sharpness across most of the APS-C field; relatively wide aperture; CA under control
Cons: Bland before PP; soft corners on APS-C
Sharpness: 8    Aberrations: 8    Bokeh: 7    Handling: 9    Value: 7    Camera Used: K-x, K5, K-01   

I acquired this lens used from KEH, as I wanted a relatively
small manual-focus 20mm prime with exposure automation to
complement an M20/4 and a Super Takumar 20/4.5. The A20/2.8
renders in a more modern style than the old Super Takumar, with
greater contrast and sharpness. Compared to the M20/4, however,
the A20/2.8 produces images that tend to be blander unless
post-processing is applied. Nevertheless, while the M20/4 has a
complicated wavy distortion that is hard to correct, the
A20/2.8 exhibits a simple barrel distortion, easily dealt with
when necessary.

The MTF curve for the A20/2.8 shows a downwards dip
15mm out from the center, right where the corners of the APS-C
frame are located, and then actually increases moving further
out to the full frame, particularly when the lens is stopped
down. The softness at the corners on APS-C may be noticeable,
especially compared to the sharpness in the center of the

For casual use, I do not bother with a lens hood, as the
A20/2.8 is quite resistant to flare. My copy came from KEH with
the original front cap that looks as if it could have been
styled by Marc Newson.
PEG Moderator

Registered: August, 2008
Location: Highlands of Scotland
Posts: 53,302

1 user found this helpful
Lens Review Date: May 5, 2013 I can recommend this lens: Yes | Price: $465.00 | Rating: 9 

Pros: Small, sharp, lightweight
Cons: None so far
Sharpness: 9    Aberrations: 9    Bokeh: 9    Handling: 10    Value: 8    Camera Used: LX, K20D K10D   

Just recently acquired this lens second hand, a small and lightweight lens. Very sharp when stopped down a couple stops, but still usable wide open when you need too. Seems fairly tolerate to flare, as I used today in sunny conditions with out hood (on order, yet to arrive).

Quite difficult to obtain the original hood second hand, had to order new hood direct from Pentax, who only had one in Europe, but that one is on it's way to me now.

Here's a few few recent images taken in August 2018, that's five years on from original purchase and I'm still happy, these were all on a K1.


New Member

Registered: January, 2012
Location: East of France : Alsace
Posts: 11
Lens Review Date: May 5, 2012 I can recommend this lens: Yes | Price: N/A | Rating: 10 

Pros: sharp, light weight, same optical formula as FA
Cons: nothing
Sharpness: 9    Aberrations: 9    Bokeh: 8    Handling: 10    Value: 10    Camera Used: K-5   

Well, I saw the FA was better rated. It's quite possible concerning the focus but for the other...OIn fact the A as the same optic formula as the FA.
I have it since several years now and really if you find one, grap it! I often use it for uraban pictures (30mm in APS-C) and I love the contrast, colors and sharpness of the pictures.
Site Supporter

Registered: January, 2011
Location: The Canadian WetCoast
Posts: 379
Lens Review Date: December 15, 2011 I can recommend this lens: Yes | Price: N/A | Rating: 9 

Pros: IQ. Built. Size.
Cons: Expensive lens hood
Sharpness: 9    Aberrations: 9    Bokeh: 9    Handling: 10    Value: 10   

I call this mighty small SWA a "Giant killer" as its' IQ is in par with the 3X heavier and 4X expensive ZK 21/2.8. Owned and used for over 25 years without a hitch. A must for any Pentax owner who like SWA on film or WA on digital camera.
Veteran Member

Registered: July, 2007
Location: SouthWest "Regio"
Posts: 3,309

1 user found this helpful
Lens Review Date: July 17, 2011 I can recommend this lens: Yes | Price: $300.00 | Rating: 9 

Pros: usefull field of view and good IQ
Cons: none
Sharpness: 8    Aberrations: 8    Bokeh: 8    Handling: 9    Value: 9   

I read the review above (by Bringolf) and it sprung to my mind, that you cannot compare apples with pears. I would expect a 28mm lens to have more contrast and resolution. But for a 20mm lens the Pentax is hard to beat. Nicely made, with a quality build. Useful at all apertures. I like the fast f/2.8 for a wide-angle, as this gives me the option for limited fov at close distances. I also like to shoot handheld in the twilight or moody hours, which is helped by the fast aperture.
IQ is very good at all apertures - just keep in your mind, that this is not a standard fl, which should delivery higher IQ anyway.
Also, I find distortion quite acceptable and much better, than with most zooms of this fl.
Inactive Account

Registered: October, 2009
Location: Montrouge, France
Posts: 31

3 users found this helpful
Lens Review Date: July 16, 2011 I can recommend this lens: Yes | Price: $170.00 | Rating: 7 

Pros: The "A" setting
Cons: less good than the M version

I rate this lens only 7 because I think it is over rated. I own a Pentax M 28 f2.8 and the quality of images with the M is much better than with the A while the M is only rated 8.25 (but costs 60$!!!).
Images with the A are much flat. Colours are less bright. It is a standard lens while the M is a beater. Not bad but not a 8 or a 9.
Its only positive aspect vs M version: the "A" setting to be used on Pentax DSLRs.
New Member

Registered: December, 2010
Location: St. Paul, MN
Posts: 7

2 users found this helpful
Lens Review Date: March 30, 2011 I can recommend this lens: Yes | Price: $400.00 | Rating: 10 

Pros: Sharp!, reasonable distortions, f/2.8, size, love the focal length
Cons: None
Sharpness: 10    Aberrations: 7    Bokeh: 7    Handling: 10    Value: 10   

Purchased in 1990 for just under $400.

This was my No. 1 lens for films. It replaced my M-Series 20mm f/4, which I also loved, but I really wanted f/2.8. I love this focal length and I love this lens. They'll bury me with this one.

CA very well controlled (even compared to current lenses).

People are generally blown away by the perspective and the sharpness, contrast, and color rendition of this lens. Sharp corner to corner. Blow it up to 16X20!

Foreground! Amazing hyper-focal DOF at f/8 - f/16. Flare very well controlled: Critical on this kind of FL. I don't miss a lens-hood -- I'm old-school, I always just used my hand.

Great for indoors shots and low-light conditions. f/2.8 allows Kodachrome 64 star-trails!

Some scanned KR64:

Purchased NEW. Can't find the drop-down for New/Used gents.
Add Review of SMC Pentax-A 20mm F2.8

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