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

SMC Pentax-FA 20mm F2.8

Reviews Views Date of last review
25 178,635 Thu April 15, 2021
Recommended By Average Price Average User Rating
96% of reviewers $505.95 9.21
SMC Pentax-FA 20mm F2.8

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

The smc PENTAX-FA 20mm F2.8 is the first and only autofocus 20mm prime lens available from Pentax. It shares the optics with its A-series predecessor.

SMC Pentax-FA 20mm F2.8
©, sharable with attribution
Image Format
Full-frame / 35mm film
Lens Mount
Pentax K
Aperture Ring
Yes (A setting)
Automatic, 6 blades
10 elements, 9 groups
Mount Variant
Check camera compatibility
Max. Aperture
Min. Aperture
AF (screwdrive)
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
Lens Cap
Plastic clip-on
Weather Sealing
Other Features
Diam x Length
70 x 44 mm (2.8 x 1.7 in.)
255 g (9 oz.)
Production Years
1995 to 2004
Launch Price
$500 USD
Engraved Name
smc PENTAX-FA 1:2.8 20mm
Product Code
User reviews
In-depth review
Screwdrive AutofocusAperture RingAutomatic ApertureFull-Frame SupportDiscontinued
In-Depth Review: Read our SMC Pentax-FA 20mm F2.8 in-depth review!
Sample Photos: View Sample Photos
Price History:

Add Review of SMC Pentax-FA 20mm F2.8
Sort Reviews by: Date | Author | Rating | Recommendation | Likes (Descending) Showing Reviews 1-15 of 25
New Member

Registered: April, 2021
Posts: 16

7 users found this helpful
Review Date: April 15, 2021 Recommended | Price: $500.00 | Rating: 8 

Pros: Sharp corner to corner from f5.6.
Cons: less contrast than a 20 f4
Sharpness: 9    Aberrations: 9    Bokeh: 8    Autofocus: 9    Handling: 10    Value: 9    New or Used: Used    Camera Used: k1   

I have just acquired the FA 20mm f2.8 for my K1. I already owned the M 20mm f4.

I am reviewing (both these) because I was unable to find an adequate comparison anywhere of the FA 20 f2.8 and the M 20 f4, so I took a risk purchasing this lens. Hopefully this review will help other folk choose between these two lenses.

My results are based on taking the same landscape with buildings detail and winter trees in the distance in the corners on a full frame K1, using both the FA 20 f2.8 and the M 20 f4, from f2.8 to f11 focused at infinity. I checked that both lenses focus correctly at infinity at all apertures before commencing (so there is no obvious focus shift, which is good). Observations were made in Photoshop at 100%. (I am not posting images, because unless they are full size, which is impractical, there isn't any point.)

First the M 20 f4:
f4 soft all over. Significant light fall-off in corners.
f5.6 sharp in the centre but soft borders. Light fall-off improving.
f8 very sharp, until 10% of the borders. Within this boundary, the f4 is similarly sharp as the f2.8. To give an objective measure: A car number plate at 55 metres (on a 20mm lens the plate’s length is a mere 0.6% of the width of the frame which really is small) is just readable. Light fall-off towards the corners on the f4 is more pronounced at all apertures than the f2.8 but only slight at f8 and easily edited.

If I crop the 10% soft border on the 4, this increases the effective focal length from 20 to 24mm and the K1 file size reduces from 36 to 25mp. This is OK and excellent on my K3, but I wanted 20mm and the full K1 file size.

The FA 20 f2.8 on the K1 does not disappoint:
f2.8 Sharp border to border; softness in corners. Noticeable light fall-off towards corners but less than the M 20 f4
f3.5 Sharp border to border; mild softness in corners.
f4.5 Sharp border to border; very mild softness in only in very tips of corners
f5.6 - 8 Sharp corner to corner.
f11 just begins to soften from diffraction.

Light fall-off diminishes progressively when stopped down and is negligible at f8. CA and aberration are good.

Happily my f2.8 lens came with a hood. Being 20mm this doesn't look like it does much but as well helping with glare I think it actually helps generally to keep contrast up. As I will only use this stopped down for landscape, I can't comment on bokeh or distortion, but there is nothing obvious on the buildings in my images.

Finally, I should mention that my f2.8 had a slight decentering problem and diagonal corners were not sharp when I acquired it (used); simply disassembling the rear group and re-assembling miraculously completely resolved this and it is now perfect - rotating the group or simply reseating it must have achieved this.

In conclusion, excepting the border softness of the F4 on full frame (but does not affect APS-C users), these two lenses perform similarly and very well. The obvious advantage of the FA over M is it is fully automatic (and it seems to autofocus well). I don't mind manual for landscape but auto is obviously more versatile. It is still compact and light.

Sweeping statements that the f4 is completely inferior to the f2.8 need to be contextualised: the f4 is not up to full frame (K1) but is outstanding on APS-C (e.g. K3) where it is capable of a very sharp A2 print corner to corner; the f2.8 on a K1 is capable of a sharp corner to corner A1. Price and what you want it for will probably determine your choice.

Registered: March, 2007
Location: Toowoomba, Queensland
Posts: 23,914

2 users found this helpful
Review Date: November 21, 2019 Recommended | Price: $500.00 | Rating: 9 

Pros: Good sharpness, small and compact size, easily fits filters, fast AF
Cons: Some barrel distortion and CA, not great at f/2.8-4
Sharpness: 8    Aberrations: 7    Bokeh: 7    Autofocus: 10    Handling: 10    Value: 8    New or Used: Used    Camera Used: K-5 IIs, K-1 II   

This little performer is the wide angle lens that made a come back when the digital FF camera came on board. Prior to that it was the DA 15 Ltd all the way.

The FA 20 on FF is what the DA 15 is on APS-C. Both are compact, and perform quite well on their respective cameras. There is a slight difference in rendering between the two, though. The FA has that characteristic film-like warmness, whilst the DA renders more cool and crisp images, with my close favourite being the DA in this regard. Similarly, sharpness is better overall with the DA particularly at the wider end of the apertures, where the FA just lacks pop and contrast.

Otherwise, at f/5.6-11, this is a solid performer on FF. It is the bridge between the ultra-wide Rokinon 14mm and the FA 31 Ltd that I have. I have not capitulated on the DFA 15-30 as yet, but as others have said, the IQ on this beast is significantly better than the FA 20. The DFA being built like a tank wouldn't have as much a problem with taking a beating compared to the non-WR FA. Does the 15-30 replace the FA 20? Only if the size and weight aren't much of a factor, or WR is required.

So overall, this FA 20, with its nimble structure and function does impress, even if the IQ is not on par with the modern lenses. 8+ out of 10, rounded up to 9.

Registered: July, 2011
Location: Melbourne
Posts: 1,219

4 users found this helpful
Review Date: September 30, 2019 Recommended | Price: $500.00 | Rating: 10 

Pros: Wide field of view without looking too real estate interior false
Cons: none
New or Used: New   

A lens I have owned since new when I loved it on the Z1, the 20mm was an easy lens to to live with. During the digital APS-C era I let it sit in the cupboard while I played with the zoom lenses. Now with the full frame digital available it has come back into the camera bag. I was surprised with the shallowness of the depth of field, with such a wide lens I expected much more depth even at wide apertures, this made isolating the subject easy. It is a lens from the film era that I have become attached to again thanks to the field of view on the full frame K1, more proof that any holes in the current lens line up can be filled with some of the quality older glass. The contrast the lens shows , even when shot under harsh lighting conditions is impressive. Black and white conversions from the raw file really worked well, with clouds in the sky showing up nicely. I must confess to not using the dedicated lens hood often enough, this was due to my laziness at not wanting to screw in the saucer like hood for what seemed like mostly little effect, I did manage to get some image degradation in one shot and the rainbow apertures in the picture appealed to me. The small size of the lens even with a 67mm filter thread also made for easy handling, the manual focus ring has plenty of throw making is easy to obtain accurate focus when required, the AF was quick enough and until I started writing this I never really gave the AF speed or accuracy a second thought, always a good sign. I didn't feel the need to try it on the K3 as I was enjoying the wide shots too much, perhaps down the track I will try it again on APS-C. Any deficiency in the images were down to me and definitly not the lens, this one has moved up in my ratings now that the K1 makes it shine again.

tied up by Gary Wakeling, on Flickr

last seat view by Gary Wakeling, on Flickr

those eyes by Gary Wakeling, on Flickr

burra night by Gary Wakeling, on Flickr

web day by Gary Wakeling, on Flickr
Forum Member

Registered: February, 2011
Location: Santa Rosa,CA
Posts: 79

1 user found this helpful
Review Date: August 13, 2019 Recommended | Price: $465.00 | Rating: 10 

Pros: Wide angle wide clear aperture wide grin on my face.
Cons: Aperture ring sticks badly but I just leave it on "A" and let the camera decide.
Sharpness: 9    Aberrations: 9    Bokeh: 8    Autofocus: 10    Handling: 10    New or Used: Used    Camera Used: Pentax K-1   

I have owned a few wide angle lenses but this one takes the cake. With f2.8 at its widest the lens isn't overly sharp. Although my night shots come out amazing. Stopping down to 5.6 is where it sings in daylight. Sharpness is great but bokeh isn't, but really it's a wide angle not for portraits. I wish my 17-28 was as close focusing, but that's another story. Great lens!
New Member

Registered: February, 2019
Posts: 6
Review Date: May 22, 2019 Not Recommended | Price: $625.00 | Rating: 4 

Pros: light weight, small, auto focus not bad
Cons: expensive, not sharp at all
Sharpness: 6    Aberrations: 7    Bokeh: 7    Autofocus: 8    Handling: 9    Value: 3    New or Used: Used    Camera Used: pentax k1   

I just received my mint copy 20mm lens from Japan. sharpness can not compare to FA *24mm at all. Is it a bad copy or 20mm lens does not perform well on full frame? 16-50mm is a much better lens on aps-c camera if SDM not a concern.
Loyal Site Supporter

Registered: October, 2018
Location: Quebec City, Quebec
Posts: 5,109

1 user found this helpful
Review Date: March 4, 2019 Recommended | Price: $500.00 | Rating: 10 

Pros: Very useful focal length on the K1 for architecture. Sharp and contrasty.
Cons: Expensive and difficult to find used.
Sharpness: 10    Aberrations: 9    Bokeh: 6    Autofocus: 10    Handling: 10    Value: 10    New or Used: Used    Camera Used: Pentax K1   

Perfect for architectural photography, here Mission San Xavier del Bac, Tucson, Arizona (top) and Cap-de-la Madeleine Basilica, Trois-Rivières, Québec.

The "Master of space". Pentax K1 + FA 20 mm f/2.8

Picture taken on a tripod, 30 seconds @ f/16 with a K1. Essential for WA rendition on FF.

Parochial cemetery, Pentax K1 + FA 20 mm f/2.8 + CPL

Cactus Garden, Mission San Xavier del Bac, Pentax K1 + FA 20 mm f/2.8
Junior Member

Registered: May, 2013
Posts: 47
Review Date: November 29, 2018 Recommended | Rating: N/A 

Pros: Sharp and good colour rendition
Sharpness: 9    Aberrations: 9    Bokeh: 8    Autofocus: 8    Handling: 9    Value: 10    New or Used: Used    Camera Used: Pentax k1   

I bought this lens used from eBay. I have used it for more than a year now. At f8 or more the lens is very sharp . You can print big prints and still get great produces subtle colours more like the film era. I like it for wide portraits.
Veteran Member

Registered: November, 2012
Posts: 963

1 user found this helpful
Review Date: February 6, 2018 Recommended | Price: $100.00 | Rating: 9 

Pros: Relatively “small”
Cons: Build quality leaves much to be desired
Sharpness: 9    Aberrations: 9    Bokeh: 9    Autofocus: 8    Handling: 7    Value: 9    New or Used: Used    Camera Used: Kx, K30, K3   

I got my copy at a relatively bargain price.

The middle group of the lens seems slightly fogged up, but it doesn’t seem to affect the images.

At 2.8 this lens lacks contrast and pop. At 2.8, the images it produce are rather disappointing. The lack of contrast can be mistaken for lack of sharpness. Not to mention, it tends to underexpose. At 2.8, indeed, the lens begs for some PP help.

At f/4, things begin to brighten up a lot, contrast goes up considerably, and colors begin to come alive.

At f/5.6, and f/8, this lens fulfill its promise. Wonderful, sharp, contrasty yet providing that distinct film-like images, easily distinguishable from the images of my DA21. Bokeh is relatively smooth, though maybe nothing special.

What I find best about it is the lens seems to love close focusing!

At the end of the day, an easy 9/10 lens.
Veteran Member

Registered: June, 2007
Location: SE Idaho - Rocky Mtns
Posts: 580

2 users found this helpful
Review Date: April 10, 2017 Recommended | Price: $600.00 | Rating: 10 

Pros: Color & Contrast
Cons: Some barrel distortion
Sharpness: 10    Aberrations: 9    Bokeh: 9    Autofocus: 9    Handling: 10    Value: 10    New or Used: Used    Camera Used: K1   

Found this lens in Japan in mint condition. Very pleased with its performance on my K-3 II as a '30mm' . I purchased this to use with my K1 when it arrives. Will update review then.

Edit: 10/13/2017 Now using on my K-1 ... Awesome performance. Very happy with this lens in full frame. Would not change my review in any respect.
Site Supporter

Registered: February, 2012
Location: Adelaide Hills, South Australia
Posts: 10,592

6 users found this helpful
Review Date: March 21, 2017 Recommended | Rating: 9 

Pros: Excellent IQ, fast AF, super compact
Cons: Significant barrel distortion
Sharpness: 10    Aberrations: 9    Bokeh: 8    Autofocus: 9    Handling: 9    Value: 9    New or Used: New    Camera Used: K-1   

Just a great lens. My DFA15-30 is better optically, but the FA20 is tiny and takes regular 67mm filters.
Worth keeping just for that.
An album of my month shooting this lens daily can be seen HERE
Site Supporter

Registered: September, 2007
Location: Near Seattle
Posts: 2,746

4 users found this helpful
Review Date: January 21, 2017 Recommended | Price: $625.00 | Rating: 7 

Pros: Compact size; f2.8; sharpness; film-like rendering; focal length for K-1
Cons: Slow AF like most older lenses; non-clinical older style of rendering that may not appeal to users unfamiliar with film-era lenses; no LR profile
Sharpness: 8    Aberrations: 6    Bokeh: 6    Autofocus: 7    Handling: 9    Value: 6    New or Used: Used    Camera Used: K-1   

I try to be conservative with my ratings above.

In early 2017, the FA 20 f2.8 is a rare treat for a K-1 owner. It's small, and lightweight. Considering how large and heavy the DFA 15-30mm lens is, this alone is reason enough to own one.

This lens feels like a bit of a throwback to the film era. The AF works just fine but it is not inspiring, not that it needs to be at this focal length. The rendering is pleasant, and has a certain film-like non-clinical look that is becoming more rare as newer "digital" lenses replace these old-style ones in K-mount.

I do wish LR had a profile for this lens, but I've been getting by using the DA Ltd. 21mm profile. I don't notice much corner weirdness.There is noticeable purple and green fringing that software fixes to some extent, but as an older lens this should not be surprising. Handling is OK considering that the FA style is, well, strange. At this focal length I just don't have to manually focus much, so the narrow focusing ring doesn't bother me like it does on the FA-50 for example. The lens seems quite sturdy overall.

It's a great lens to take hiking because of the smaller size and perfect focal length for big scenes. I've also gotten some highly satisfying PixelShift images with the K-1 as well as fun HDR images.

Hope this is useful, thanks for reading.


f2.8 @ 1/6, ISO 800

f8 @ 1/60, ISO 200

f6.7 @ 1/20, ISO 400, PixelShifted

f6.7, 1/20, ISO 800 3x HDR
Junior Member

Registered: January, 2013
Location: Texas
Posts: 32

1 user found this helpful
Review Date: June 21, 2016 Recommended | Rating: 9 

Pros: Weight, build quality
Cons: Focusing ring
Sharpness: 9    Aberrations: 9    Bokeh: 9    Autofocus: 10    Handling: 8    Value: 8    New or Used: New    Camera Used: Pentax ZX, K10D, K30   

Usable at f2.8 (limited distortion and vignetting, okay sharpness), really excellent at f5.6.
Slightly better than A 24mm f2.8.
Well build, light.
The only thing I dislike is the focusing ring: too thin, badly located, rubbery.

Registered: April, 2015
Location: USA
Posts: 2,813

5 users found this helpful
Review Date: January 17, 2016 Recommended | Price: $400.00 | Rating: 10 

Pros: Sharpness, contrast, 3D depth, lightweight
Cons: Colors not as good as the limiteds
Sharpness: 10    Aberrations: 10    Bokeh: 9    Handling: 10    Value: 9    New or Used: New   

Senior Member

Registered: July, 2009
Location: South Florida
Posts: 206
Review Date: July 8, 2013 Recommended | Price: $660.00 | Rating: 10 

Pros: Sharp, beautiful colors, size.
Cons: None
Sharpness: 10    Aberrations: 10    Bokeh: 10    Autofocus: 10    Handling: 10    Value: 10    New or Used: Used    Camera Used: K-5, K0-1   

I own the DA 15, the DA 10-17 and the Sigma 30 f1.4 but this is now my go to lens for general shooting. It rarely leaves my camera. The colors are gorgeous and even the black and white images I have shot with lens appear crisper, with better contrast, very filmlike. I love it for close up portraits, street scenes and landscapes.
Veteran Member

Registered: January, 2007
Location: Warsaw
Posts: 338

7 users found this helpful
Review Date: November 30, 2012 Recommended | Price: $500.00 | Rating: 8 

Pros: Colour quality and sharpness
Cons: some distortion
Sharpness: 9    Aberrations: 8    Bokeh: 6    Autofocus: 7    Handling: 8    Value: 8    New or Used: Used    Camera Used: K20D, K5   

Before I bought FA20/2.8 I used A20/2.8. They look to be identical construction. So it is sharp lens, with good color rendition. Probably best Pentax 20mm lens ever made.

more samples here
Add Review of SMC Pentax-FA 20mm F2.8

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