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SMC Pentax-DA* 50-135mm F2.8 ED [IF] SDM

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150 494,046 Mon January 4, 2021
Recommended By Average Price Average User Rating
94% of reviewers $800.41 9.01
SMC Pentax-DA* 50-135mm F2.8 ED [IF] SDM

SMC Pentax-DA* 50-135mm F2.8 ED [IF] SDM
SMC Pentax-DA* 50-135mm F2.8 ED [IF] SDM

Like all current DA lenses, the SMC Pentax DA* 50-135mm is designed only for Pentax APS-C DSLR cameras. It was announced in late February, 2007. It auto-focuses with an SDM ultrasonic motor on the K10D (firmware 1.30) and newer cameras. On older cameras the lens will auto-focus with the 'screw drive' mechanism.

SMC Pentax-DA* 50-135mm F2.8 ED [IF]
©, sharable with attribution
Image Format
Lens Mount
Pentax K
Aperture Ring
Automatic, 9 blades
18 elements, 14 groups
Mount Variant
Check camera compatibility
Max. Aperture
Min. Aperture
AF (in-lens motor or screwdrive)
Min. Focus
100 cm
Max. Magnification
Filter Size
67 mm
Internal Focus
Field of View (Diag. / Horiz.)

APS-C: 31.5-11.9 ° / 27-10 °
PH-RBK 67 mm
Lens Cap
Weather Sealing
Yes (AW)
Other Features
AF/MF Switch,Internal Zoom
Diam x Length
77 x 136 mm (3 x 5.4 in.)
685 g (24.2 oz.)
w/ Hood: +80g
Production Years
2007 to present (in production)
$796 USD current price
Engraved Name
smc PENTAX-DA* 1:2.8 50-135mm ED [IF] SDM
Product Code
User reviews
In-depth review
Unofficial Full-Frame Compatibility Tests by Pentax Forums
★☆☆ Usable with reservations at select F-stop/focal length combinations
Show details
Internal zoom.
Three ED elements.

Screwdrive AutofocusSupersonic AutofocusQuick ShiftWeather SealedInternal FocusingInternal ZoomingAutomatic ApertureAPS-C Digital Only
Purchase: Buy the SMC Pentax-DA* 50-135mm F2.8 ED [IF] SDM
In-Depth Review: Read our SMC Pentax-DA* 50-135mm F2.8 ED [IF] SDM in-depth review!
Sample Photos: View Sample Photos

Add Review of SMC Pentax-DA* 50-135mm F2.8 ED [IF] SDM Buy the SMC Pentax-DA* 50-135mm F2.8 ED [IF] SDM
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Site Supporter

Registered: May, 2016
Location: Bristol, Tennessee
Posts: 156

1 user found this helpful
Lens Review Date: January 4, 2021 I can recommend this lens: Yes | Price: $405.00 | Rating: 9 

Pros: well built, compact, nice bokeh
Cons: auto focus issues, soft wide open
Sharpness: 8    Aberrations: 9    Bokeh: 9    Autofocus: 7    Handling: 9    Value: 8    New or Used: Used    Camera Used: K3   

This lens is sturdy and well built, yet compact enough to take with you for when you need a bit more reach. This is a great lens for portraits. I have used it mostly for portrait sessions or as my long lens before I obtained my DA* 60-250 F4. I had a DA 55-300 before I had the DA* 50-135, and I almost always preferred a cropped picture from the DA* 50-135 over an uncropped DA 55-300, so much so that I stopped carrying the DA 55-300, unless I knew I was going to be at the extreme end. On the other hand, I can't say I'd leave the house ever with just this lens unless I was only doing portraits, because I'm almost always wanting a bit wider shot than it can provide. So if you're doing portraits, this is a great choice. If you're doing anything else, it's a great second lens.

Registered: November, 2013
Location: Barcelona
Posts: 478
Lens Review Date: October 4, 2020 I can recommend this lens: Yes | Price: $450.00 | Rating: 8 

Pros: Quality Image, decent AF, non heavy at all. Images pop up
Cons: AF is quite slow for sports. SDM usually fails
Sharpness: 9    Aberrations: 8    Bokeh: 10    Autofocus: 7    Handling: 10    Value: 9    New or Used: Used    Camera Used: K3, K5, K3II   

I bought my copy knowing the SDM motor was broken.
So following a tutorial I have converted it to screwdrive mount.

I don't care much as I use to use my lenses for motorsport.

This lens is great. The image quality is fantastic and the bokeh even at F4 is delicious.
Yet, for my taste, my likes and the use I give it to its a bit too slow in the AF. I have shoot motorsports with it and can do the work, the range is fantastic in apsc (70-200mm equivalent) and its not heavy at all. But that AF is not the best. My Sigma 100-300mm f4 beats it every day, and I wonder if the Sigma 70-200mm f2.8 would beat it easily every other day also.

Yet it creates delicious images when doing portraits

_IMG6969 by Daniel Gonzalez Aguilera, en Flickr

_IMG6964 by Daniel Gonzalez Aguilera, en Flickr

IMGP6516 by Daniel Gonzalez Aguilera, en Flickr

It does work well in low light environments

_IMG5980 by Daniel Gonzalez Aguilera, en Flickr

_IMG6048 by Daniel Gonzalez Aguilera, en Flickr

IMGP6575 by Daniel Gonzalez Aguilera, en Flickr

And for motorsport purposes if you are close enough to action, you get good results. (my copy has even been champagne sprayed into)

_IMG2015 by Daniel Gonzalez Aguilera, en Flickr

_IMG1678 by Daniel Gonzalez Aguilera, en Flickr

_IMG0473 by Daniel Gonzalez Aguilera, en Flickr

_IMG0347 by Daniel Gonzalez Aguilera, en Flickr

_IMG0327 by Daniel Gonzalez Aguilera, en Flickr

_IMG0435 by Daniel Gonzalez Aguilera, en Flickr

_IMG0235 by Daniel Gonzalez Aguilera, en Flickr

IMGP6558 by Daniel Gonzalez Aguilera, en Flickr

It is also a Grid Killer, shoots thru glass in the cars as a knife in butter. Smooth and silent, but precise.

IMGP6634 by Daniel Gonzalez Aguilera, en Flickr

_IMG2898 by Daniel Gonzalez Aguilera, en Flickr

IMGP6744 by Daniel Gonzalez Aguilera, en Flickr

_IMG2958 by Daniel Gonzalez Aguilera, en Flickr

_IMG3016 by Daniel Gonzalez Aguilera, en Flickr

_IMG3048 by Daniel Gonzalez Aguilera, en Flickr

The best part for motorsport is that it is quite a compact lens so it is not intrusive to anybody having a chat, or working.
Yet as I said before I doubt wheter a Sigma 70-200mm f2.8 would work better for me.

This is a lens that is no wonder if you can carry it around as its light weight, no issue to add it in the backpack for a weekend with the 2 cameras, flash/es, long lens short lens, laptop and so on.
New Member

Registered: January, 2020
Posts: 5

1 user found this helpful
Lens Review Date: May 8, 2020 I can recommend this lens: Yes | Price: $257.00 | Rating: 9 

Pros: Beauty lens , Sharp
Cons: Af
Sharpness: 9    Aberrations: 9    Bokeh: 9    Autofocus: 7    Handling: 8    Value: 9    New or Used: Used   

Site Supporter

Registered: January, 2013
Location: Ottawa, Canada
Posts: 2,826

2 users found this helpful
Lens Review Date: April 15, 2020 I can recommend this lens: Yes | Price: $850.00 | Rating: 9 

Pros: Optical qualities, Size, Focal length range, 'all weather'
Cons: Autofocus (see below)
Sharpness: 9    Aberrations: 9    Bokeh: 10    Autofocus: 7    Handling: 9    Value: 9    New or Used: New    Camera Used: K-3 II, K-5 II   

The Pentax DA* 50-135 was one of the first lenses that I bought in late-2011 after getting my new K-7, and it has been one of my most-used lenses. As a lens that I rarely leave at home, it easily receives c.a.m’s 4.5-star Gold rating of Highly Recommended!

The optical qualities are excellent. The lens is sharp across the field, with very good performance even in the corners at most settings. While the lens is usable wide open across the focal length range, I’ve noticed a slight softness at f/2.8 compared to other commonly-used apertures, especially at the longer end. However, I’ve never had a concern about distortion, vignetting, or aberrations, and the colours, contrast, and overall rendering are superb. In particular, the bokeh is typically pleasing at wide apertures.

At a mass of just under 700 grams, I find this lens to be comfortable to carry and handle. It is significantly smaller and lighter than my Sigma 70-200 f/2.8 HSM – which illustrates a strong benefit of the APS-C format. It’s a versatile lens that pairs nicely with my DA 20-40mm Limited. The lens has proven itself in a variety of shooting environments, including trail hikes, cityscapes, concerts, and portraits.

My copy was afflicted by autofocus issues four times during 2012-2013, during the height of many user reports of ‘SDM failure’. Warranty work included two new motors, cleaning, adjustments, calibration, and “gearing and clutch cam ring” repair. On the fifth instance, the AF seized again and the lens could not be focused manually. At that point, I converted the lens to ‘screwdrive’ mode, and it has worked flawlessly ever since.

I have conducted a rigorous AF Fine Adjustment (AFFA) calibration, assessing the settings at 50, 90, and 135mm; at focus distances of at least 30 x focal length; and variably focusing from the minimum focus distance and infinity positions. I found that the optimal AFFA setting varied according to focal length and focus direction; the optimal setting that gives the sharpest autofocus at all focal lengths is AFFA = +3 when focused from the near position. So, I simply preset the focus to the near side of the subject before each shot, which is an extra step but not a big deal. Note, however, that the AFFA is a function of both the lens and the camera acting together, so this issue may not be entirely a fault of the lens itself. This detail – and the SDM issue – is reflected in my lower rating of ‘7’ for AF.

The AF accuracy is typically spot-on and the shot-to-shot focus consistency is very good. I tend to take pictures mainly of static subjects, and I find that the autofocus is sufficiently quick and assured on my K-3 II. I don’t find that the screwdrive movement is annoyingly noisy, but it’s certainly more noticeable than the nearly-silent SDM mode. On the other hand, the screwdrive focus action is somewhat faster than the SDM, and it works.

- Craig

New Member

Registered: November, 2018
Posts: 1
Lens Review Date: February 19, 2020 I can recommend this lens: Yes | Price: $400.00 | Rating: 8 

Pros: sharp from 3.5; reasonable size and weight
Cons: slow autofocus; a bit soft at 2.8
Sharpness: 8    Aberrations: 9    Bokeh: 9    Autofocus: 7    Handling: 8    Value: 9    New or Used: Used    Camera Used: K-70   

Decent size and weight, well balanced on my K-70. Good sharpness from f3.5 but a bit soft wide open at 2.8. Autofocus is a bit slow but OK to use as portrait lens. Like many other users reported, my copy does not work well with the HD 1.4x teleconverter (rather soft until f6.3).
Site Supporter

Registered: November, 2014
Location: Washington, DC
Posts: 1,635

3 users found this helpful
Lens Review Date: January 10, 2020 I can recommend this lens: Yes | Price: $400.00 | Rating: 9 

Pros: Rendering; focal range; sharpness
Cons: autofocus

This was my first 'pro' level lens, and WOW is it a good lens! I had been using my HD DA 55-300 as an event lens, as it runs (if I remember correctly) around an f/4-4.5 for a good portion of its range. I found myself needing the extra stop of light indoors, and so I sprung for this lens. I was at first concerned, coming from the 55-300, that this zoom range would be restricting. This has not proved to be an issue in the least! It is a very versatile range with good quality.

I got it used with a failed SDM and had it converted by our good 'ol local Pentax Forums convertor, and now it runs great on screwdrive. It has a weird thing still that at 90mm it will back/front focus horribly - so I learned to avoid that focal length for autofocus. The focus isn't great, and I find it difficult to trust at f/2.8. Especially at 135mm, which isn't quite as sharp as the other focal lengths, it is easy to miss the focus by a hair. So I generally shoot at f/4, but f/2.8 is indoors doable with care, a monopod helps.

The rendition and colors are fantastic, so is the sharpness. It is a great lens. I've started taking this and the DA21 limited as a simple fairly compact two lens combo for events, and it works out really nicely. It has proven leagues above the HD DA 55-300, but there are still some impediments that I deal with for the low price I got it for.
Senior Member

Registered: June, 2018
Posts: 129

1 user found this helpful
Lens Review Date: January 8, 2020 I can recommend this lens: Yes | Price: N/A | Rating: 8 

Pros: Useful zoom range, good IQ
Cons: I’ll be upset if the autofocus packs up.
Sharpness: 8    Aberrations: 9    Bokeh: 8    Autofocus: 7    Handling: 7    Value: 8    New or Used: Used    Camera Used: K3ii   

I had the Sigma 50-150mm f2.8 but it wouldn’t work properly on my K3ii so I replaced it with this. I’m very pleased I did. Both are sharp but I much prefer the colours on this and I like that it is weather sealed too. It’s large but not unwieldy and autofocus is only slightly slower than I would like. It could be sharper wide open but it’s much better from f4.

Registered: September, 2017
Location: New York
Posts: 1,170

1 user found this helpful
Lens Review Date: November 29, 2019 I can recommend this lens: Yes | Price: $650.00 | Rating: 9 

Pros: Sharpness, Color, contrast, build quality, overall image quality, silent focusing, lack of CA, lack of PF, bokeh
Cons: Focusing speed
Sharpness: 9    Aberrations: 8    Bokeh: 10    Autofocus: 7    Handling: 10    Value: 10    New or Used: Used    Camera Used: Pentax K-3II   

I hold this lens in very high regard and I don't take my camera gear anywhere without packing this lens too. It's possibly my most used lens. While I can't say it's the sharpest, it's definitely very sharp. The colors produced are fantastic and need barely any touching in post. Bokeh can seem a bit busy in certain circumstances but otherwise is very nice as well. Autofocus is definitely kind of slow but it also has a very long focus throw. If the throw was shorter, autofocus would definitely be faster. That said, the lens acquires lock quickly and is very quiet. I only hear a very low squeak when starting.

All told, it is the one lens I absolutely love using and the one I do not want to do without. If Pentax ever upgrades the lens while keeping the IQ the same, I will definitely be purchasing it.
Junior Member

Registered: May, 2012
Posts: 30
Lens Review Date: October 2, 2019 I can recommend this lens: No | Price: $2,500.00 | Rating: 9 

Pros: muy afilado. punto dulce... 90mm - f4
Cons: motor de enfoque se pego temprano
Sharpness: 9    Aberrations: 8    Bokeh: 9    Autofocus: 3    Handling: 8    Value: 5    New or Used: New    Camera Used: k20 -k5   

a pesar de que lo utilizo en MF ya que se pego el motor de enfoque ,lo compraría nuevamente por su calidad de imagen excepcional
Senior Member

Registered: May, 2010
Location: WA
Posts: 167

3 users found this helpful
Lens Review Date: October 1, 2019 I can recommend this lens: Yes | Price: $455.00 | Rating: 10 

Cons: Some report AF issues

I rented this lens in 2015 for a weekend trip to a race track. I needed a lens with moderate range, great image quality, and decent low light performance. My previous lens were good kit lens, the 18-135mm and the 55-300mm.

This lens surpassed all of my expectations.

Image Quality is fantastic. Great colors, excellent contrast, and sharp photos. I was amazed to see my test shot of a race car 500 feet away come out sharp. The lens rarely came off the camera the rest of the weekend. I came away with larger amount of sharp photos than I had previously done. The autofocus was great, weight was fine for hand shooting.

By the end of the year, I made sure to purchase my own copy. It has since been my go to lens, more so than my Tameron 70-200 F2.8.

My only complaint is that it stops at 135mm.

Site Supporter

Registered: March, 2016
Location: Pietermaritzburg
Posts: 402

1 user found this helpful
Lens Review Date: July 28, 2019 I can recommend this lens: Yes | Price: $400.00 | Rating: 10 

Pros: Sharp, great bokeh, great IQ
Cons: Slow(ish) autofocus
Sharpness: 10    Aberrations: 10    Bokeh: 10    Autofocus: 8    Handling: 10    Value: 10    New or Used: Used    Camera Used: K20D, Kx, K3   

This is by far the best lens I’ve ever owned. It’s fast and sharp, with a beautiful bokeh. I bought this together with my K20D, second-hand for $700! At the time I didn’t really know what * series lenses were, but found out pretty quickly!

From flowers to wildlife to landscapes, this is a versatile lens. It has macro like sharpness at the closest focal distance, and yet will give good IQ at longer ranges too. Because of this you can crop fairly tightly and still get a good photo. I've used it with the 1.4x rear converter, but it seems to soften the image slightly?

The fact that the barrel doesn’t extend when zooming or focusing makes it impervious to dust, drizzle and snow. Although it’s not what you’d call light, I prefer the solid, well-constructed feel of the lens, and the weight makes it well balanced to boot.

In conclusion, all I can say is that if I was forced to sell off all my gear, this would be the last to go.

Roadside Flowers

Goodyear Eagles

Spotted Eagle Owl
Senior Member

Registered: November, 2017
Location: Sydney, NSW
Posts: 114
Lens Review Date: July 5, 2019 I can recommend this lens: Yes | Price: $300.00 | Rating: 9 

Pros: all weather, internal zoom, internal focus, parfocal zoom lens
Cons: inconsistent and slow auto-focus
Sharpness: 9    Aberrations: 10    Bokeh: 10    Autofocus: 6    Handling: 10    Value: 9    New or Used: Used    Camera Used: Pentax KP   

I bought this lens secondhand. It is mainly used for landscape as well as indoor/outdoor events. Occasionally, I will use it for portraiture.

Overall, the lens delivers great optical performance. Its sharpness is good wide-open and great from f/3.5 to f/8 throughout the zoom range. I cannot remember any issue with CA using this lens. Further, it produces the smooth and pleasing out of focus area.

In term of lens construction and handling, the lens is well-built. Its zoom ring is in an adequate size for my hand. The focus ring offers a large area to grip on when a manual focus is needed, which requires about 135 degrees of turn to change from its minimum focusing distance at 1m to infinity or vice versa. This long focus throw allows a high degree of accurancy when focus manually. The AF switch on the lens allows catch-in-focus. I have not yet brought the lens through any harsh condition, but it can withstand light rain many times without any issue.

The only problem I find in this lens is its auto-focus. Although silent in sound, its auto-focus is slow and somewhat inconsistent (especially in case of a contrast-based auto-focus in live view). If the lens has not been used for a very long time, it may need a bit of warm-up period, where an auto-focus is slower than usual, before it can operate at the normal speed. Sometimes, auto-focus with this lens does not give an accurate result. Also, the lens may miss the focus from time to time, which is really annoying. When the auto-focus is hit, however, it can deliver great results.

To mitigate the misfocus issue, I would recommend zooming all the way in first in order to acquire focus. Then you may zoom out and compose the image. From my own experience, I believe this lens is a parfocal zoom lens, i.e., the focus distance does not change when the zoom ring is rotated and the focal length is changed.
New Member

Registered: February, 2010
Location: Roma
Posts: 1
Lens Review Date: March 22, 2019 I can recommend this lens: Yes | Price: $780.00 | Rating: 9 

Pros: Color, sharpness, bokeh
Cons: No FF, SDM life
Sharpness: 10    Aberrations: 9    Bokeh: 9    Autofocus: 8    Handling: 9    Value: 9    New or Used: New    Camera Used: K20D, K3, KS2, K1   

I bought it in Greek new @ less than 800$, it was a great deal !

But...before end the warranty autofous stop operation first time, it was repair in France free of charging, after 5 years broken again and spent around 300€

Great lens for portrait, color and saturation are magic, autofocus is slow but (when is working) is very precise (so in my country is called the Sloth)
I love short tele, so in APS-C for me over 100 mm is too much for portrait, but good to get photo in sports in small field or sometime in landscape where chromatic aberration are well controlled !

For reason eplained above I prefer the FA 77/1.8 Limited to it, but the Sloth is more versatile, aboslute best in CA, wheather sealed well balance when is monted on K3 for example.

I tested with K1, but as you know is useable in FF @ 135 mm over f/8, even do in crop mode for portrait is still valid, is the right range in full frame, it's a shame we don't use it in FF mode, for those reason I decide to sell it.

Best lens for APS-C!
Loyal Site Supporter

Registered: October, 2018
Location: Quebec City, Quebec
Posts: 2,247
Lens Review Date: March 18, 2019 I can recommend this lens: Yes | Price: $1,000.00 | Rating: 9 

Pros: Sharp and contrasty, internal focusing.
Cons: Prone to flare.
Sharpness: 10    Aberrations: 8    Bokeh: 9    Autofocus: 10    Handling: 10    Value: 9    New or Used: New    Camera Used: Pentax K5, K3   

Batiscan River in the Fall, Notre-Dame-des-Anges

Downtown Montreal at night

Fall foliage, Saint Leonard

Quebec City from the Observatory (above @ 50 mm, below @ 135 mm)

Forum Member

Registered: April, 2018
Location: Tartu
Posts: 78

5 users found this helpful
Lens Review Date: December 19, 2018 I can recommend this lens: Yes | Price: $500.00 | Rating: 9 

Pros: light weight - weathersealed - sharpness - bokeh
Cons: slow AF
Sharpness: 9    Aberrations: 9    Bokeh: 10    Autofocus: 7    Handling: 10    Value: 10    New or Used: Used    Camera Used: K50 & K3 & K1   

Pentax DA*50-135 F2,8

My thoughts after 18months of use.
(not a review, I don't have the necessary know-how and equipment to review a lens.)

Ergonomics and design
  • Very good size and weight. You can definitely carry it around all day, even shoot one handed on the wider end.
  • The weathersealing is tight. It will even survive underwater for some time. (don't ask me, just know it's not completely watertight :P) In rain, no question.
  • The grips are from rubber and real tight. The rubber hasn't slipped once even after I've removed it from the zoom ring various times. (why? Keep reading)
  • The resistance on both the zoom and focusing rings are good. No complaints there.
  • The hood is long and tough. It might seem sometimes it doesn't attach properly, but in real use it has never come loose so no lost points there. I'm actually glad it's big. Makes you feel bigger and helps keep the contrast.
  • This lens has an dedicated MF/AF switch. I don't use it much at all because in addition it has quickshift: you can use manual focus in AF.
  • Mounted on a tripod (a rather cheap one ~50$) it doesn't move in landscape orientation. When I turn my ballhead 90 to the side (portrait orientation) it has a hard time keeping steady and sometimes starts sliding. So a tripod collar would have been nice with this lens :/
  • The housing is made from metal and the paint hasn't started coming off from any parts. My copy is almost 8 years old and it still looks like a mint one from the outside.

  • It's okay. The bokeh is smooth (no onion rings etc) and keeps it's round shape throughout it's apertures.
  • There is some aberration, but very minor and mostly goes unnoticed.
  • Haze is under control when shooting into a bright light source. Don't expect anything exceptional though. You'll still lose a lot of detail in the shadows as with most lenses.
  • Sharpness at f2,8 isn't the best, but from f3,5 it's tack sharp until f11~f13 where it gets soft again.

Compared to Tamron 17-50/f2.8 and Pentax-M 50/1.4 all at f5.6, I'd say the 50-135 takes a close second behind the 50/1.4, but well ahead of the Tamron (which is a very sharp zoom lens).

*When I started photography, I noticed many people telling something like "shoot with a kit lens at f8 and it's as sharp as premium glass wide open". I have to disagree Even though it's a bit hazy at 2,8 there's a lot more fine detail visible. So don't trust that misbelief.

  • It's slow. There's no point in sugarcoating it. Not ideal for close range fast paced action @f2,8.
  • For everything else, it's more than enough. Goes from infinity to close focus in just over a second.
  • Sometimes it feels a bit laggy and has trouble locking focus.
  • More rarely, the lens might start and take the first couple of shots a little out of focus. Usually this issue goes away with a few seconds of focusing(AF).

*People have also pointed out it's not precise. I have to disagree. Having used a K30, K500, K50 and now a K3, the issue lies inherently within Pentax's own AF system. I can never be 100% sure I'll get pixel perfect focus. There's always a small room within which the AF system misses and catches focus and it has done so with all my cameras and different lenses. With fast glass these tiny errors show up more.
**My copy of this lens needed AF microadjustment. More on the older bodies, less on the K3.

Problems and FIXES

Let's start with the big one:

SDM failure

The good news is that in most cases the SDM doesn't die, it simply gets stuck. If you can't fix it via warranty and don't want to convert this lens into a screwdrive one, there is a simple fix available. I've made a separate blog post about it here: LINK

*this happened to me once and I fixed it

focus locks up

Turning the screwdrive screw on the back of your lens should do the trick.

*this happened to me once

Misses focus on some focal length, but not others

This indicates the zoom ring pins are bent or broken. See my link above, I also talked about this in my post. Again, it's an easy fix that doesn't require any mayor lens disassembly.

*never happened to me

Doesn't find any focus at all, only focuses inside a narrow range and doesn't respond to manual focus

I don't know why this happened, but I've read once or twice about it online too so I'm not the only one.
I just took the lens off and afterwards it worked perfectly again.

*this happened to me once

You might think this lens comes with a fair share of potential problems, but I assure you, all of them are rather rare and every lens regardless of manufacturer has problems like that. Newer copies of this lens have a better SDM that doesn't get stuck so easily. After doing a lot of research and meddling with the interior of my lens I'm convinced this lens won't magically break. For everything that happens there's a reason and most of the time the fixes are rather easy.

I recommend this lens. It's probably the best APS-C zoom lens for Pentax.

*I also tested it on the K1. The lenshood produces a good chunk of the vignette. Without the lenshood you can shoot @50mm and do a 1,1~1,2x crop to get rid of the dark edges. 1:1 crop has no vignette. Really, the vignette is not that bad without the hood. Works as a FF lens in the higher mm range. AND it remains sharp. So, no need to sell it just because you upgraded to a K1.
Add Review of SMC Pentax-DA* 50-135mm F2.8 ED [IF] SDM Buy the SMC Pentax-DA* 50-135mm F2.8 ED [IF] SDM

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