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SMC Pentax-A 645 55mm F2.8 Review RSS Feed

SMC Pentax-A 645 55mm F2.8

Reviews Views Date of last review
11 69,325 Tue February 8, 2022
Recommended By Average Price Average User Rating
100% of reviewers $181.18 8.91
SMC Pentax-A 645 55mm F2.8


Moderate wide angle lens in the 645 film format and more of a normal lens on a 645 digital camera. This is a manual focus lens.

smc Pentax-A 645 55mm F2.8
©, sharable with attribution
Image Format
645 film
Lens Mount
Pentax 645
Aperture Ring
Yes (A setting)
Automatic, 8 blades
8 elements, 7 groups
Mount Variant
645 A
Check camera compatibility
Max. Aperture
Min. Aperture
Min. Focus
45 cm
Max. Magnification
Filter Size
58 mm
Internal Focus
Field of View (Diag. / Horiz.)

645 Digital: 53 ° / 44 °
645 Film: 65 ° / 54 °
RH-B 58mm screw-in
Lens Cap
Plastic clip-on
Weather Sealing
Other Features
Diam x Length
74 x 60.5 mm (2.9 x 2.4 in.)
410 g (w/o attachments) (14.5 oz.)
Production Years
Engraved Name
smc PENTAX-A 645 1:2.8 55mm
User reviews
Manual FocusAperture RingAutomatic ApertureMedium-Format SupportAdapter needed for DSLRsDiscontinued
Price History:

Add Review of SMC Pentax-A 645 55mm F2.8
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Site Supporter

Registered: January, 2022
Location: London
Posts: 118

1 user found this helpful
Review Date: February 8, 2022 Recommended | Price: $300.00 | Rating: 8 

Pros: Excellent centre sharpness, very well controlled flare, low CA, nice bokeh, exquisite build quality
Cons: Comparatively weak corners
Sharpness: 8    Aberrations: 7    Bokeh: 7    Handling: 10    Value: 9    Camera Used: Fujifilm GFX50R, Pentax 645Z, Pentax 645   

I wanted this lens primarily to use it as my relatively fast normal "walk-about" prime on my Fujifilm GFX50R (initially) and Pentax 645Z, i.e., for those occasions when I might want to use this camera hand-held on "photo walks" (all my other medium-format lenses are slower and heavier and I typically only use them on a tripod).

I came across a pristine, "new-old-stock" unit in Japan, complete with its box, lens case and original paperwork and blank warranty (!), and so I could not resist :-)

After using it for a while, I can confirm that its main strengths are: excellent centre sharpness at all apertures, extremely good resistance to flare (I am using a B+W metal hood, though, which I suppose helps), and well controlled chromatic aberrations, both longitudinal and axial. And of course, the build quality is exquisite, like virtually all Pentax-A 645 lenses.

As for weaknesses... the image corners are a bit smeary at f/2.8, and never fully sharpen up properly even at f/5.6. This doesn't really bother me too much, since when I use it at its widest apertures, it's typically hand-held, to isolate a main subject which is usually fairly centrally located, so the corners are out of focus anyway. But flat, frame-filling subjects would suffer. Relative peak performance across the frame is attained at f/8 - 11, where the issue *almost* disappears and the whole image is acceptably sharp.

Finally, the bokeh: while not "creamy smooth" like that of some other lenses, I find it very pleasing nonetheless - please see the samples below to get an idea.

Overall, I must say that I like it very much. It serves my main intended purpose very well, and it is just a joy to handle and use.

Loyal Site Supporter

Registered: October, 2018
Location: Quebec City, Quebec
Posts: 6,212

1 user found this helpful
Review Date: December 1, 2019 Recommended | Price: $159.00 | Rating: 10 

Pros: Sharp at middle apertures, splendid colors and contrast.
Cons: Infinity resolution a little weak.
Sharpness: 9    Aberrations: 9    Bokeh: 7    Handling: 10    Value: 10    Camera Used: PENTAX 645Z   

Pictures taken between f/8 and f/11 in Aperture-priority mode. These fast A-series lenses are built to last a lifetime and are a delight to use. Performance remains constant between f/5.6 and f/16. Rendering of details at infinity is a little disappointing. I ordered a newer DFA 55 mm f/2.8 AF lens and I will compare the performance of both side by side.

@ f/8

@ f/11

@ f/9 "Hic domus Dei est"

@ f/11
New Member

Registered: September, 2018
Posts: 1

1 user found this helpful
Review Date: October 9, 2018 Recommended | Price: $189.00 | Rating: 10 

Pros: Great wide angle
Sharpness: 10    Aberrations: 9    Bokeh: 6    Handling: 10    Value: 10    Camera Used: Pentax 645NII   

I am used to using a 45mm pancake Zeiss on my contax 35mm which is my preferred lens for portability and super sharpness. I recently purchased this to complement longer focal length lens I normally use with my pentax medium format. What I especially like is how wide it is yet you can get very close to something and get a really tight close up. Flare? You shouldnít be using this with a digital camera. That like putting caviar on Ritz crackers.
Loyal Site Supporter

Registered: October, 2012
Location: Medina, OH
Posts: 7,219
Review Date: June 26, 2017 Recommended | Price: $75.00 | Rating: 9 

Pros: Sharpness, smooth rendering, ease of focussing.
Cons: Flare

I am using on K-1 with cheap Chinese adapter, which is all you need because the expensive adapters provide no more functionality, although I wish my adapter had a tripod socket to allow tripod use with the heavier 645 lenses. This lens was the first of the 645s that I have tried on digital full-frame. I have not even used it on my 645 or 645N.

With the adapter, there is no communication with the camera. However, you can use AV (aperture priority) and forget about the green button metering. The reason is that you set the desired aperture on the A ring, and the aperture remains open at this aperture for automatic light metering. I customarily use AV mode and then adjust exposure on the K-1 by using the top dial set to exposure compensation (+/-) as needed. This works well for me and is pretty easy once you get used to it. For focussing, you are focussing using the aperture set at your desired aperture, and with AV mode the camera automatically gives you the correct exposure. It also means that the viewfinder will be pretty dark at smaller apertures, so you may have to focus at a larger aperture and then stop down to take the shot. I have not had to do this yet, but am prepared to do so if necessary.
The lens feels great in use. Build quality is awesome, and the lens presents as a permanent piece of equipment. One advantage of using the lens on full-frame instead of native 645 is that is focusses closer than on native 645 film cameras. Focussing scale on lens indicates 18 inches as closest focus, but with the added length of the adapter I am down to what appears to be bout 10 inches. Eight inches closer focus may not seem important, but it is what moves the lens close enough to the subject that it approaches macro status, and this close focus capability really enhances the use of the lens for flowers, my primary photographic area of interest. I would highly recommend the lens to others who want to use it for blossoms.

This lens seems to sell on eBay for $150 to $400. I got a real deal at $75 from Keh who marked the lens BGN which means UGLY, but the lens I received would have been ranked excellent by most other vendors of used photographic equipment. There was not a mark on the lens, and the only negative was lack of hood and front and back caps.

Tactilely, the lens is a pleasure. It is a little heavier than the cognate 135 lens would be, but still not a burden on the K-1, at least not to me. Focus ring moves easily with the long throw typical of MF lenses in general. I focus through the viewfinder and watch for the green light and audible beep, and focussing this way makes focussing an easy task for me. I hardly ever have missed focus with this lens.

The worst aspect of this lens is flare as demonstrated in the first photo I have posted. I suspect that flare problems are increased in some way by use of the adapter and/or use of the lens on a full-frame vs native 645 format. With outside flower photography you usually do not get flare when the lens is pointed downward toward the flower subject. However, the minute you point the lens upward, particularly if your viewfinder picks up some part of the sky, flare results. The after-market hood I am using is not adequate to the task, but I can often eliminate flare by cupping my hand around the top of the lens of by holding my big black cavalry hat above the lens. I wish I could find a big 77mm hood, maybe something like the monster that comer with the 85mm FA f 1.4, but I will probably wind up with one of those smaller metal screw-in hoods, and will add a taped-together black construction paper hood to solve the problem. I will appreciate hearing from anyone who has confronted and solved the flare problem.

NOTE: Since the original review, I have solved the flare problem by spray painting the inside of the adapter with black matte paint and adding a cheap screw-in hood.

is lens.
Forum Member

Registered: August, 2015
Posts: 62
Review Date: August 17, 2016 Recommended | Price: $240.00 | Rating: 8 

Pros: Well built, not too heavy
Cons: Not the best on a 33x44mm sensor
Sharpness: 8    Aberrations: 7    Bokeh: 9    Handling: 10    Value: 8    Camera Used: Sony A7r, then Fuji GFX 50R   

Note: The forum doesn't allow multiple posts. I've had this lens on two different sized sensors (full frame and 33x44mm), with two different experiences. I've downgraded my evaluation based on the GFX 50R experience, documented below, but I left the original review.

On the Sony A7R

This is a really good lens. I was nervous about buying one because reviews are not unambiguously positive, and it's not spoken of much outside this forum. I'm glad I took the chance. I wanted something faster and lighter than my fantastic 45-85/4.5 SMC Pentax-A 645 zoom. This fits the bill.

Iím using this lens on a Sony A7r with a pair of Mirex tilt-shift adapters. The Pentax 645 to Canon EOS Mirex adapter plugs into a Canon EOS to Sony E Mirex adapter. Pentax-A 645 lenses on this setup give me a large range of camera movements.

I tested this lens against an ISO 12233 chart, for close performance, a brick wall, for medium distance, and a distant landscape, for infinity. To get a comparative perspective, I duplicated all tests on my SMC Pentax-A 645 45-85mm f/4.5 at 55mm and my Super-Multi-Coated Takumar 55mm f/1.8 lenses (both terrific lenses).

Colour is typical SMC Pentax-A 645. Bokeh is very smooth. In terms of sharpness across apertures, on my A7r, f/2.8 is not terrific. I'd describe it as soft and a bit "glowy". However, f/4 is much better (at all distances). It doesn't have a click stop in between f/2.8 and f/4, but you can still set a half-way aperture, and it's already much less soft and glowy than f/2.8. The best apertures are f/5.6 and f/8, at close, medium and infinity. However, I would not hesitate to use the lens at f/11 for critical work at any distance. Even f/16 is quite usable at all distances. I find that f/22 is too soft, even for emergencies (due to diffraction).

The previous reviewer wrote about field curvature issues in the extreme corners when focused at infinity. I looked hard for this problem, but didnít notice anything I found objectionable or even unusual. To be fair though, I almost never focus at infinity because Iím using the lens with tilt-shift adapter (and I shoot a lot of landscape). The previous reviewer wrote also about difficulty hitting infinity with his copy. On my copy, I hit the infinity mark right at infinity Ė which is actually unusual in my kit. On my Mirex adapter, some of my other SMC Pentax-A lenses focus past infinity and some hit it bang on.

The SMC Pentax-A 645 45-85mm f/4.5 is a really strong performer at 55mm, so itís a good baseline. The 55mm f/2.8 SMC Pentax-A 645 is on par. I really didnít see any significant differences at all distances and common apertures. Comparing against the Super-Multi-Coated Takumar 55mm f/1.8 reinforced for me how good that lens is. It might even be sharper in the centre than the 645 lenses at f/8. The Takumar doesnít have strong corner performance until f/8 Ė but it costs a fraction of what the 645 lenses cost.

In conclusion, Iím glad I took a chance on the SMC Pentax-A 645 55mm f/2.8. Itís a nice addition to my set of 645 primes.

EDIT: After additional real world use and some more testing and comparison against other lenses, I've determined that if you need absolutely every last bit of sharpness, use the SMC Pentax-A 645 45-85mm f/4.5. It's a bit sharper overall at 55mm (but honestly you really have to look closely at the test chart!). The 45-85mm lens is also a bit better in the corners than the 55mm. I compared both of these to the SMC Pentax-A 35mm f/3.5, and that's unquestionably better everywhere (centre, edges, corner). The bottom-line remains the same though: the SMC Pentax-A 645 55mm f/2.8 is a solid performer -- not as good as the 35mm f/3.5, but few lenses are.

On the Fuji GFX 50R

A lot of what I said for the A7R still holds true, especially the mechanical side. It is a very nice lens to use. Unfortunately, where it performed quite well on an A7R, it does less well on the larger GFX 50R sensor. It's quite sharp in the centre portion of the frame, but it never gets excellent in the corners. It's quite usable unshifted at f/11, but that's not really acceptable. Things don't improve when shifting -- the further you shift the worse it gets. It will shift 15mm in the long direction, which is very good. But the edges and corners get worse.

If you're not shifting it, and you don't care about corner performance, then you can be happy with this lens. But I bought it to give me a light option at 55mm for my tilt-shift outfit, so I need solid image quality everywhere. This lens doesn't provide that.

If you need something in the 55mm range in Pentax 645, get the 45-85mm f/4.5 zoom. It's an excellent performer on the GFX 50 sensor. I don't love the weight of the zoom, but it does not let me down. From f/5.6 on it's a strong performer from the centre to the corners, and image quality stays strong during shifts. My copy is an A.
New Member

Registered: August, 2015
Posts: 1
Review Date: August 7, 2015 Recommended | Price: $200.00 | Rating: 8 

Pros: Sharpness at the center
Cons: Field curvature, CAs at the corner
Sharpness: 8    Aberrations: 7    Bokeh: 8    Handling: 10    Value: 9    Camera Used: 645D, Nikon D800   

I bought this lens at B&H used dept.
I gave 8 because of the sharpness decrease at corners when I focus at infinite (see below for detail). Other than that, this lens is really good. I would recommend this lens except those who frequently focus at infinite.

The sharpness at the center is impressive though the corner is fair because of slight field curvature and CAs. Because of this characteristic, I would not suggest it to use for landscape photography especially if you want to focus at infinite; when you focus precisely at the center, corner is focused slightly on the foreground.
When you focus on something finite object, this lens perform pretty nicely with a f-stop of 2.8. As far as I know, D FA has the same characteristic, by the way.
To make the matter worse, my copy cannot exceed infinite at center to have corners focused at infinite. I guess the infinite point can be adjustable.

Aberrations are fairly controlled though I can see field curvatures and some CAs.

Bokeh are fairly smooth, but you can see some blue or cyan fringing in background.

Handling is really nice; it's really handy and light.

Value was nice.

Registered: April, 2009
Location: Madrid, Spain
Posts: 10,449

2 users found this helpful
Review Date: September 3, 2014 Recommended | Price: $140.00 | Rating: 9 

Pros: Well built, sharp
Cons: None
Sharpness: 10    Aberrations: 10    Bokeh: 10    Handling: 10    Value: 8    Camera Used: Pentax 645 (original)   

I chose the 55mm lens over the 45mm as it's a more suitable focal length for general use - aprox. 35mm equivalent rather than aprox. 28mm.

The lens is quite big and heavy but handles very well and, as far as I can tell from my Epson V500 scans, is very sharp wide open. That's important for me on medium format as I like the shallow depth of field that's possible with medium format and f/2.8 in terms of exposure is not that fast.

I don't see any distortion and bokeh seems smooth as far as I can tell. The build quality is very good though the focusing ring on my copy is a little loose, but not enough to make it fiddly to use.

A few example photos.

Pro 160NS, P645 003a
by Jonathan_in_Madrid, on Flickr

Pro 160NS, P645 004a
by Jonathan_in_Madrid, on Flickr

T-Max 100 P645 2014 012a
by Jonathan_in_Madrid, on Flickr
New Member

Registered: December, 2010
Location: Huntsville, AL
Posts: 16

1 user found this helpful
Review Date: August 6, 2012 Recommended | Price: $150.00 | Rating: 10 

Pros: Sharp, f2.8, inexpensive
Cons: none
Sharpness: 10    Aberrations: 10    Bokeh: 10    Handling: 10    Value: 10    Camera Used: K200D   

I usually use with DSLR (K200D) with adapter. Looks like around 70mm with DSLR. The best lens I have.

Sample photos:

Veteran Member

Registered: October, 2008
Location: Albuquerque NM
Posts: 9,830
Review Date: May 5, 2010 Recommended | Price: $90.00 | Rating: 9 

Pros: Sharp and compact
Cons: Not reall wide, but so what.

I purchased this lens dirt cheap because it did show signs of ong years of use, including a tiny mark on the far edge of one of the elements. However, it works beatifully.

This lens is an unsung contributer to the 645 line. It is said to be the equivalent in FOV of a 35mm lens on film, and this is not a FOV I have used a lot over the years (other than in a pocket film camera) so it does not feel very wide. However, I have no complaints about the results.

The shot of the tractor below was taken on Fuji Neopan Acros 100 developed in Rodinal--a combo that can resolve about as much as a lens can give. The crop below is a 100% crop from a 4,000 dpi scan (around 2" from a 29" wide print) and may not even be the precise point of focus. This lens holds its own very well.

New Member

Registered: March, 2009
Location: Tennessee
Posts: 3
Review Date: May 21, 2009 Recommended | Price: $250.00 | Rating: 7 

Pros: Macro bellows with this lens is superior
Cons: 58mm filter size and infrequently used angle of view for me

Unsung hero of 645 macro bellows. This is a good, sturdy, well-made wide angle lens.

I almost never carry it because I favor the 645 35mm. However, I have noticed that with the 645 Auto Bellows, this lens design offers one of the best, most convenient combinations of aperture and magnification.

I have no qualms with its construction; I simply favor the 645 35mm.

This lens also works well with 645 Adapter K on my 35mm film and DSLR equipment.

I find the 58mm filter size inconvenient; probably just a personal preference; but, in medium format equipment, it's just easier to setup everything for 77mm, in my opinion.

Well made and sturdy; an okay wide angle lens; but, this lens really shines in macro bellows applications. I use this lens when I want no-nonsense magnification. If you need more than this lens and a bellows, get a powerful microscope.

I estimate angle of view for this lens at roughly half of my 645 35mm: this one is one handspan high at arm's length on the short side, and two handspans at arm's length on the long side. That's when directly bayonetted onto the 645.

Overall, a good lens.
Site Supporter

Registered: November, 2008
Location: Washington DC, USA
Posts: 631
Review Date: May 15, 2009 Recommended | Price: $200.00 | Rating: 10 

Pros: Small and light weight. Fast f/2.8 aperture.
Cons: Lack of a dedicated, rigid hood.

A very nice, compact and sharp wide angle. Feels solid, but not heavy. Construction is beautiful. The only drawback for me is the lack of a dedicated, rigid lens hood. I have a third party, aluminum hood for it that does not vignette, however, I am not certain if it is a perfect fit to maximize flare reduction. Overall fantastic.
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