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SMC Pentax-A 400mm F5.6

Reviews Views Date of last review
19 91,352 Mon August 31, 2020
Recommended By Average Price Average User Rating
100% of reviewers $395.89 8.58
SMC Pentax-A 400mm F5.6

SMC Pentax-A 400mm F5.6
SMC Pentax-A 400mm F5.6

The SMC Pentax-A 400mm F5.6 lens is a compact extreme-telephoto lens featuring a tripod collar and built-in hood. Manual focus, auto aperture.

SMC Pentax-A 400mm F5.6
©, sharable with attribution
Image Format
Full-frame / 35mm film
Lens Mount
Pentax K
Aperture Ring
Yes (A setting)
Automatic, 9 blades
7 elements, 6 groups
Mount Variant
Check camera compatibility
Max. Aperture
Min. Aperture
Min. Focus
280 cm
Max. Magnification
Filter Size
77 mm
Internal Focus
Field of View (Diag. / Horiz.)

APS-C: 4.1 ° / 3.4 °
Full frame: 6.2 ° / 5.2 °
Built-in, slide out
Hard case HE-330
Lens Cap
Plastic clip-on
Weather Sealing
Other Features
Tripod Mount
Diam x Length
85 x 277 mm
1240 g
Production Years
1984 to 2004
Engraved Name
smc PENTAX-A 1:5.6 400mm
Product Code
User reviews
Manual FocusBuilt-in HoodAperture RingAutomatic ApertureFull-Frame SupportDiscontinued
Price History:

Add Review of SMC Pentax-A 400mm F5.6
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Forum Member

Registered: July, 2020
Posts: 77
Lens Review Date: August 31, 2020 I can recommend this lens: Yes | Price: $586.00 | Rating: 9 

Pros: light and relatively compact; excellent build and design; very sharp; easy to focus; built-in lens hood; aperture priority
Cons: some chromatic aberration; aperture ring tight against camera when mounted
Sharpness: 10    Aberrations: 4    Bokeh: 7    Handling: 9    Value: 10    Camera Used: K10D, K3 II   

I got this chiefly for astrophotography, so that's what my review is based on. I did photograph a nearby brick chimney as soon as I got the lens for testing purposes, which showed it's sharpness (and from which I rated the bokeh above, though I don't buy long telephotos for bokeh), but the real sharpness comes in shots of the moon -- which are exceptional in showing crater details. The slower speed (f/5.6) keeps the lens smaller and lighter, and it's not a problem for me because I'm using a tripod anyway (and an iOptron clock drive for much/most of my astrophotography). The tripod foot is well-placed and balances well the weight of the front part of the barrel with lenses and my K-3 II or K10D cameras; a nice design feature is the screw-in knob that allows rotation of the barrel with the camera mounted, so that you can quickly change from landscape mode (horizontal) to portrait mode (vertical) when on a tripod.

I like the focusing on this lens, which rotates about 330-340 degrees (i.e., almost a complete turn between infinity and closest focus); it's fairly easy to fine-tweak the focus with the big focusing ring to get sharpness in lunar-crater details, for example, though it's harder to get focus on Saturn or Jupiter and its Galilean satellites, because they are fainter objects (and atmospheric seeing affects their images a lot). The rings of Saturn aren't resolvable with this lens and my K10D (which is heavily pixelated with only 10.2 megapixels, even at ISO 100), though you can see the darker gaps between the planet and the rings. The 24-megapixel sensor in the K-3 II is somewhat better for resolution. I found the closest focus to be pretty amazing for a 400-mm telephoto lens: about 7.5 feet (= 2.2 meters) from the front lens. The aperture ring has a really nice movement and feel, and goes from f/5.6 to f/45 (!); in typical Pentax-design fashion, the aperture ring is right up against the camera when mounted, which is ergonomically not the best design because it's a bit of a tight fit for fingers (but the aperture-priority option negates the need to move the aperture ring on all Pentax DSLRs).

There is some purple fringing on part of the lunar edge, which I have in all my older-than-F Pentax telephoto lenses that are longer than 135mm. The chromatic aberration is the only significant issue in these lenses, to me (the size and weight is a given to me, so I don't put that down as a negative aspect) -- but for my purposes, the CA doesn't particularly bother me (and you can largely eliminate it with image processing afterwards). Some other reviewers might lower the overall score because of the chromatic aberration in this lens, but the positives outweigh the CA for me by a long shot, and if not for the CA, I'd rate this lens a "10". This lens does need a tripod, but I still give it a "9" for handling because we're talking a 400-mm lens here -- and it's a really well-handling lens for that focal length; I don't feel that you can realistically judge the handling of a 400-mm lens vs. that of a 28-mm f/2.8 lens. Yes, the tube is long, but you're getting a much lighter, much cheaper lens than you'd get with a 400-mm f/2.8 lens with the much larger glass. The actual objective glass is about 70 mm in diameter; as stated in the table of specs above, the outside tube diameter (meaning the outside of the retractable hood) is about 85 mm (so a solar filter that does not screw in as a 77-mm filter would need to fit around this 85-mm exterior diameter).

Some people reviewing this lens here say that they can use this 400-mm f/5.6 lens hand-held, and my response to that is: (a) it shows how relatively light the lens is and (b) be fortunate that your hands are that steady, because I need a tripod always for lenses like this. [I edited my review to change the price from $530 to $586, adding in the cost of the official Pentax felt-lined hard case for this lens that I didn't get with the lens but was able to purchase separately off Ebay. All my stated costs in my reviews include shipping costs and taxes where relevant. I see that i paid more than most reviewers here, sometimes by hundreds of dollars, but to me the lens is so good and easy to use that it's worth what I paid -- not that I'd be unhappier if I had paid $200 less, of course!]

I'm an avid solar-eclipse chaser and have not had the chance to use this yet on eclipses. I've gotten sharp photos with a solar filter, and this will likely be my one of my telephoto lens (out of three or four prime telephotos) set up at the next eclipse. My Pentax smc 500-mm f/4.5 lens is likely to also see eclipse action, but it's much heavier and takes much more patience to set up than does the 400-mm f/5.6 (though the 500-mm is extremely sharp also). I expect that this 400-mm lens will produce impressive images of the solar corona during a total solar eclipse, being just about the perfect focal length to get the fainter outer corona.

Photos of the lens on my camera, showing the hood retracted and extended:

Photo of the red planet Mars to the upper left of the just-past-full moon around 2h35m UT on 2020 Oct. 3. Taken with K-3 II camera plus this 400-mm f/5.6 lens at 1/125 sec and f/8 on a tripod (full-size image to show scale of moon with this lens in an APS-C frame; JPEG converted from original RAW image):

Site Supporter

Registered: June, 2013
Location: Utrecht
Posts: 53

2 users found this helpful
Lens Review Date: December 11, 2019 I can recommend this lens: Yes | Price: $300.00 | Rating: 9 

Pros: Very sharp at F8-11, sturdy build, tripod, close focus
Cons: As it is manual focus, so not very fast in handling
Sharpness: 9    Aberrations: 8    Bokeh: 10    Handling: 8    Value: 9    Camera Used: K1ii and K-01   

The A400 is a very nice and solid lens. I bought it as an upgrade for my K300 F4 and RMC Tokina F5.6. The A400 has better IQ then the K300 for aberrations and is a little bit sharper overall then theTokina is. All three lenses are sturdy build, the K300 has the nicest looks and the most attractive coatings. I had some fungus in the center between the front elements and I had to do some small destructive cutting to get it unscrewed, but it is fully operationalnow and very clear and bright. See also my post how I managed that.

K-01 shots both taken at F8, 1/180 sec (bright moon) resp 2 sec (blood moon). The latter is less sharp due to the movement of the moon...

Dec 2019 addition: I use it now on Full Frame K1ii,this lens even shines more on it then on APS-C. APS-C shots in fact are physical crops of what this lens was intended for. On full frame this lens delivers real nice equally sharp pictures on your screen.

Shot taken on 225 meters distance at F8 ISO 1600:

Cropped x5:

Loyal Site Supporter

Registered: February, 2014
Location: Pennsylvania
Posts: 1,361

4 users found this helpful
Lens Review Date: August 27, 2019 I can recommend this lens: Yes | Price: $385.00 | Rating: 8 

Pros: Build quality, IQ at middle apertures, Bokeh
Cons: Not sharp until F 8-11, Slow focusing
Sharpness: 8    Aberrations: 8    Bokeh: 9    Handling: 8    Value: 8    Camera Used: K-5iis, K-3   

I’ve owned two almost mint condition copies of this lens, both performing nearly identically.

The SMC-A 400 f5.6 has a number of things going for it. The build quality, typical of all A series lenses, is impeccable. Reasonably compact, with a built in tripod collar and lens hood, it travels well. Colors are saturated and warm, Another A series trait. No green button metering either, this lens communicates fully with modern digital Pentax bodies. Image quality and sharpness can be very good to excellent if you hit the “sweet spot” of close to medium distance and apertures between f9 to f13 or so. Flare is very well controlled, even when shooting a strong point light source.

I really wanted to love this lens, unfortunately it just doesn’t deliver the goods in these areas. Focusing is quite slow. The focus throw is very long and somewhat heavily damped, great for tripod use on stationary subjects but far from ideal handheld or for fast moving subjects. Performance at f5.6 to f8 is so-so at best.
Frame filling close subjects which require minimal enlargement in PP can look reasonably good. Subjects more than twenty yards or so away often look very soft, showing little fine detail. Not an ideal birding lens. Some color fringing is also evident in strongly lit, high contrast situations, though at f11 this is minimized.

The deciding factor to wether you will like the A 400 f5.6 comes down to cost vs. performance. Pentax doesn’t give one many viable options when it comes to long telephoto lenses. The excellent but exceedingly expensive and rare f2.8 400 mm lenses and the D FA 150-450mm which is also expensive are there for well heeled photographers. The older Takumar, SMC K and SMC M 400’s are less expensive but suffer from many more performance comprises and often have hazing or fungus issues. Third party 400mm’s are hard to find and usually aren’t particularly good. This leaves the A 400 f5.6 in a zone all by itself. Purchased between $300 to $425 or so, the lens represents a pretty good value in price vs. performance. Plus, you will never wear one out.
New Member

Registered: February, 2010
Location: Cincinnati
Posts: 22
Lens Review Date: December 2, 2018 I can recommend this lens: Yes | Price: $250.00 | Rating: 8 

Pros: Quality Build and Feel, Nice images
Cons: Heavy and long thus hard to hand hold and focus
Sharpness: 8    Aberrations: 8    Bokeh: 8    Handling: 6    Value: 9    Camera Used: Pentax K-3   

Just tested this lens:
SMC Pentax-A 400mm F5.6 USED cost about $250:
SMC Pentax-DA* 300mm F4 ED [IF] SDM with a 1.4x HD PENTAX-DA AF Rear Converter. (effective 420mm F 5.6 in this combination)
USED cost about $1250

Results Pentax-DA* 300mm with TC were the best at F5.6.

BUT by F8 the SMC Pentax-A 400mm F5.6 was very similar in quality and the 400mm cost me $1,000 less.

I also tested the 400mm lens with a Pentax 1.7X AF teleconverter. In spite of this being only a F5.6 lens it would auto-focus well with the teleconverter. The image quality went down when compared to the 300mm with the new 1.4X HD teleconverter.
Site Supporter

Registered: December, 2015
Location: Kaua'i
Posts: 46
Lens Review Date: June 7, 2018 I can recommend this lens: Yes | Price: $350.00 | Rating: 9 

Pros: Lightweight, Simple
Sharpness: 8    Aberrations: 8    Bokeh: 7    Handling: 10    Value: 10   

I love it. Especially for the investment. Light enough that shooting hand held on the fly isn't an issue. Would recommend for someone looking to experiment with zoom landscape photography, though would only suggest for action/birding type shots to someone a little experienced in shooting manual lenses. The zoom works really well, and is very smooth on my copy, but could be better focus throw for flying birds etc.
Site Supporter

Registered: November, 2009
Location: Weyburn SK
Posts: 30
Lens Review Date: January 24, 2018 I can recommend this lens: Yes | Price: $350.00 | Rating: 8 

Pros: Nice feel to lens, focus ring is nice to use.
Cons: A bite long when you pull out the shade.
Sharpness: 8    Aberrations: 8    Bokeh: 8    Handling: 7    Value: 9    Camera Used: K5ii   

Work well hand held in good light. Have also used with a 1.4 converter with tripod shooting the moon. the tripod collar is a real plus and works well. It also is a conversation lens around other people in a crowd. Mine came with lens case also, got from ebay 2 years ago.
Site Supporter

Registered: June, 2013
Location: Montreal, Canada
Posts: 537

4 users found this helpful
Lens Review Date: October 22, 2017 I can recommend this lens: Yes | Price: $270.00 | Rating: 10 

Pros: Very sharp, easy focus for a manual lens
Cons: CA, contrast

An affordable very sharp long lens. I bought it for shooting the eclipse and wasn't disappointed. I find making focus is easy with this lens. On my K-5 focus confirmation signal is very precise so I can even risk taking birds in flight! ... with about a rate of succes of 1 in 20. But for a slower moving subject I get really good results. The star field below was taken at f/5.6 and shows virtually no coma in the corners. It is a stack of several frames so it is slightly cropped. Without ED elements in the lens, you have to deal with a fair amount of purple fringing in PP and work on improving contrast

The lens sure packs a lot of bang for the bucks.

Senior Member

Registered: October, 2015
Location: Washington
Posts: 267

3 users found this helpful
Lens Review Date: July 16, 2016 I can recommend this lens: Yes | Price: $400.00 | Rating: 10 

Pros: Sharp, Handling, IQ, Price
Cons: none
Sharpness: 10    Aberrations: 8    Bokeh: 9    Handling: 10    Value: 10    Camera Used: K-3, K-1   

I always wanted this lens. I got it on E-Bay.
Lens came with carrying case. It is built solid. Good old Pentax metal body lens..built to last.
It is light enough for handheld shooting. That was the main reason I bought it. I have much larger
SMC 500mm f/4.5 and that one require tripod. With this SMC A 400mm f/5.6 I have more freedom to
walk around and shoot. Image quality is very very good. Better than I expected. It is a "A" lens, so shooting is pretty simple , especially in TAV mode (Aperture and Speed priority). All you have to do is focus.
Focusing ring is silky smooth. I just love older Pentax lenses.
I highly recommend this lens for someone looking for a nice prime lens with decent range and don't mind manual focus.
Here are some samples.

IMGP8823 by Ludovit Tatos, on Flickr

IMGP8880 by Ludovit Tatos, on Flickr

IMGP8738 by Ludovit Tatos, on Flickr
Veteran Member

Registered: October, 2008
Location: Albuquerque NM
Posts: 9,830

4 users found this helpful
Lens Review Date: February 21, 2016 I can recommend this lens: Yes | Price: $400.00 | Rating: 9 

Pros: Sharp, works with all automation modes, not huge
Cons: Focus emphasizes accuracy rather than speed
Sharpness: 9    Aberrations: 9    Bokeh: 8    Handling: 7    Value: 10    Camera Used: Pentax K3, Sony A7R   

The lens is a long, skinny, sturdy metal package with a handy tripod mount and built-in lens cap. The focus feel is excellent, but the throw is long, making a fast focus on moving objects more of a challenge, but allowing very precise focus on stationary subjects.

I have used this on Pentax film and APS-C bodies, and now the Sony A7R. I can't say I really saw what this lens could do until I mounted it on the full frame 36mp A7R body. It is sharp all the way across, but a little PP is needed to punch up the contrast.

The Photos below are full frame, and show best when viewed on Flickr, rather than the small version which displays here with the link.

The last photo of the small bird below was taken with the A400 plus the 1.4x-L converter of similar vintage for an effective 560mm. These two were made for each other, and they work very well either on cropped or full frame sensors. The detail on the small bird is amazing given the converter.

New Member

Registered: April, 2015
Posts: 1

4 users found this helpful
Lens Review Date: April 8, 2015 I can recommend this lens: Yes | Price: $550.00 | Rating: 8 

Pros: lightweight, high PQ ratio, easy to find in second hand market
Cons: not internal focusing, not sharp at wide open, not physically balance when mount on tripod
Sharpness: 8    Aberrations: 7    Bokeh: 7    Handling: 9    Value: 10    Camera Used: K5iis   

This lens is not designed for tracking fast moving object in view of its long range of focusing distances and f/5.6 maximum aperture. It does suffer from purple fringing with strong backlighting.

Considering its relatively light weight, it is a good handheld lens for snapshot and birding.

Image quality will greatly improve when stop down to f/8 or below. When stop down to f/11, the image quality is superb and sharp.

Samples @f/11 are attached below:


Registered: August, 2011
Location: Langwarrin Australia
Posts: 382

4 users found this helpful
Lens Review Date: August 13, 2013 I can recommend this lens: Yes | Price: $390.00 | Rating: 9 

Pros: Sharpness,contrast, short minimum focus,build,value
Cons: Long slow focus
Sharpness: 9    Aberrations: 8    Bokeh: 9    Handling: 9    Value: 10    Camera Used: K5IIs   

This lens surprised me it just doesn't get the same recognition as the 300mm f4, yet it out performs it with better sharpness and contrast. Its short minimum focus also surprised me, something rarely seen in lenses of this focal length. This lens is far better than the price I paid for it, great value for money and a real sleeper.
Site Supporter

Registered: August, 2011
Location: Kansas City
Posts: 183

1 user found this helpful
Lens Review Date: May 20, 2013 I can recommend this lens: Yes | Price: $550.00 | Rating: 10 

Pros: Very sharp, comfortable handling, excellent image quality
Cons: None
Sharpness: 10    Aberrations: 9    Bokeh: 9    Handling: 10    Value: 10    Camera Used: K-5, MX   

I bought this lens from a fellow Pentax Forums member over the winter, and I have only recently had the opportunity to use this lens. I like to use a long lens to really throw the background out of contention when I want to isolate people at events and such. This weekend, I finally had my first opportunity when our city held its annual festival. With this lens, it was a piece of cake getting far enough away that people had no idea they were being photographed. I will admit at times it was nice to have this lens mounted on a monopod, mostly because I got a little tired after two or three hours of hand-holding it. That said, the built-in tripod mount collar provided a well-balanced mount. Whether hand-held or mounted, the lens was very easy and comfortable to work with. I was surprised to find that the focus ring was actually about as smooth as that of an internal-focus lens, and it made it very easy to focus precisely.

Since it is an A-series lens, it works great on my K-5 as well as on my MX. And the images are, in my opinion, pretty nice with decent bokeh and contrast and lovely color rendition. I was only able to detect the slightest chromatic aberration (see inset of picture below) from the hundred or so images I shot. Considering this lens does not boast ED glass, it's impressive that it out-performs my former Nikkor 300mm ED(IF) with regard to purple fringing (as well as overall image quality).

In short, this is a truly fun lens to use, and the image quality is excellent in my opinion.

Here are some shots from this weekend's festival. The first two shots were at f/6.3.

This next shot reveals a high-contrast area with purple fringing --

The rest of the shots, however, were just fine under close examination. This was shot wide open at f/5.6 --
Loyal Site Supporter

Registered: August, 2011
Location: North Carolina, USA
Posts: 5,123

6 users found this helpful
Lens Review Date: February 16, 2012 I can recommend this lens: Yes | Price: $550.00 | Rating: 8 

Pros: Sharp; short MFD; handles well for a 400
Cons: Some CA
Sharpness: 9    Aberrations: 7    Bokeh: 7    Handling: 9    Value: 10   

A good sharp super-tele that is easily hand-holdable, although of course with a 400mm lens a tripod is necessary to get the best results. While it's true you can't instantly change focus between near and far objects, the long focus throw and solid focus damping help to achieve precise focus, and are a good match for a MF super-tele.

The short minimum focus distance is excellent for those occasions when you can get really close to your subject. This is a slight crop:

High-contrast subjects can produce some purple fringing. Another mild crop:

A busy high-contrast background can result in nervous bokeh with bokeh CA -- here's a 100% crop from the above image, showing both purple fringing on the subject, and bokeh CA (green and purple background highlights):

I think that is something of a worst-case scenario, and in practice this is very manageable. Another example showing strong backlighting, first uncropped and then a 100% crop:

Veteran Member

Registered: July, 2007
Location: Hong Kong
Posts: 431

7 users found this helpful
Lens Review Date: October 22, 2010 I can recommend this lens: Yes | Price: N/A | Rating: 7 

Pros: Build quality, sharpness and good contrast.
Cons: Slow focusing and some purple fringing.

This is a slow lens in term of focussing speed and the aperture.
Although, it does suffer from purple fringing, nevertheless, the image quality is rather good and sharp.
Weight is not too heavy and reasonable for a 400mm tele lens. Handheld is possible.
All the sample pics below were indeed taken without a tripod or monopod.
I agreed to Ben Edict's review of this lens. If speed, fast tracking of moving object is not the primary concern (possible but not easy), this lens can be a very good choice.

Samples from this lens:

Senior Member

Registered: December, 2008
Location: Oxford, UK
Posts: 276

2 users found this helpful
Lens Review Date: April 21, 2010 I can recommend this lens: Yes | Price: $100.00 | Rating: 9 

Pros: Good IQ, good bokeh
Cons: Heavy
Sharpness: 8    Aberrations: 8    Bokeh: 8    Handling: 6    Value: 10   

I got it at an auction, so the $100 is an equal share of the price of the lot it was in.
I really, really like this lens. For me, it is definitely a tripod or mono-pod lens. As others have said, it gives sharp results and good colors. I like the bokeh.
This is one lens that I will keep until one of us can't take pictures anymore...

Shot was F8, ISO 100, 1/90.
Add Review of SMC Pentax-A 400mm F5.6

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