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Sigma 18-125mm F3.5-5.6 DC

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9 47,438 Sun April 19, 2015
Recommended By Average Price Average User Rating
100% of reviewers $155.71 8.33
Sigma 18-125mm F3.5-5.6 DC

Sigma 18-125mm F3.5-5.6 DC
Sigma 18-125mm F3.5-5.6 DC

This zoom lens was exclusively designed for use with digital Single-Lens Reflex (SLR) cameras and has 6.9 times high magnification zoom ratio. Image circle is designed to match the size of the image sensor of digital SLR cameras. A Special Low Dispersion (SLD) and two pieces of aspherical glass elements produce high level of optical performance through the entire zoom range and also this has resulted in a compact, lightweight lens. This lens has a minimum focusing distance of 50cm (19.6in.) at all focal lengths and equipped with inner focusing system. Since the front of the lens does not rotate, "Petal Shaped Hood" and a circular polarizing filter can be easily attached and used. This lens is also equipped with "Zoom Lock Switch" that eliminates "Zoom Creep."
The later HSM 18-125mm version is reviewed separately.

Focal Length 18-125mm
Minimum Aperture F22
Lens Construction 15 Elements in 14 Groups
Angle of View 69.3- 11.4
Filter Size 62 mm
Weight 385 g (13.5 oz)

Number of Diaphragm Blades 7 pcs
Minimum Focusing Distance 50 cm (19.6inches)
Dimensions (dia x len) 70 mm (2.7inches) x 77.7 mm (3inches)
Mount Type: Pentax KAF2/KAF (screwdrive AF)
Price History:

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Site Supporter

Registered: November, 2012
Location: North Wales
Posts: 2,364

1 user found this helpful
Lens Review Date: April 19, 2015 I can recommend this lens: Yes | Price: $130.00 | Rating: 8 

Pros: value, competitive performance with DA18-135
Cons: AF? iffy < 50mm; movements opposite to pentax; MF not as good as DA; slow lens: f3.5 only at 18-20mm and IQ subpar anyway
Sharpness: 8    Aberrations: 8    Handling: 8    Value: 9    Camera Used: K5   

I acquired this lens as a sub for the DA 18-135mm which came with my K5 but was sold to offset the cost. This was less than half the going price of a S/H DA18-135mm. My thinking was that a kit lens replacement like this with AF and versatile zoom range for me needs to be merely good enough. I see myself using this on holidays, family occasions etc., making use of the cameras own profiles to deliver good jpg's to be shared online (I need to look around and see if there is a profile for this lens mind you, the K5 was reporting it as a Pentax-F 28-80mm).

However while I had both I did some side by side pics to see what I was getting, or might be losing, in terms of IQ. These are my results. Note that these are all exported from LR3.6 using just default settings, I was only equalising exposure and tweaking to correct any clipping, so these pics and crops are not representative of the out-of-camera jpg's you will get with either lens. Mostly manual focus 10x LV, tripod mounted.

Specification wise the lenses really are pretty similar. I hardly noticed the 10mm difference at the long end of the focal range - IMO that would not be a reason to make a choice. They look and feel quite similar too, but are structurally distinct, focus/zoom rings rotate in opposite directions, the manual focus ring is at the mount end on the DA, at the front on the Sigma. For MF both had a better, but still rather light, feel in comparison to the rattly kit lens focus (and I thought the long throw on the DA18-135 much the better). The variable aperture on both lenses changed similarly, both already to f4 at 24mm, f4.5 at 50mm (low light? bring out the "nifty-fifty"!), f4.5 (DA) vs f5.6 (Sigma) at 70mm, f5.6 all the way thereafter. One extra feature on the Sigma is a "zoomlock switch", as far as I can tell this seems to be for storing/carrying the lens, locking it unextended at 18mm.

18mm, architecture
Neither lens for me was particularly great at 18mm, particularly wide open. Both showed pronounced vignetting at f3.5, the Sigma more so, decreasing stopping down but still present. The DA had noticeably better contrast, and for me, centre frame was a wee bit sharper. Both lenses were softer at one side, the DA at the left frame, the Sigma, more markedly, at the right frame. The improvement in IQ stopping down to f5.6 on the Sigma was significant, and the right edge, though not the centre, continued to improve to f11, which tends to be indicative of some decentering. I looked for CA at >100% at edges and contrast transitions but both lenses did pretty well on that. By f8 images from both were pretty good.
Well f3.5 is usable I suppose, but the desireability of stopping down at 18mm to improve the IQ is clear. Additionally, I noticed that when I tried AF, and then checked the focus in Live View, it wasn't necessarily, to my eyes, spot on. However I haven't fine tuned the AF for this lens so that could be the problem rather than the camera inherently struggling with the lower contrast and larger wide angle DoF at 18mm, although that wouldn't surprise me, and I note that the photozone reviewer describes the AF accuracy sub-50mm as abysmal, using a canon 350D! You have been warned, however the 350D came out in ~2005 and AF has improved a lot since then. Another technical point to note: both lenses are distinctly varifocal so focussing at a longer focal length and then zooming out doesn't work.


24mm, architecture
Both lenses showed well at 24mm, the vignetting was mostly gone, contrast and resolution up. Little to choose between them, both were already good at f4.

28mm, architecture
I used AF and oops! at f4 the Sigma was out of focus. However by f8 the image was in focus - in retrospect I noticed a slight refocus by the K5 - sharp and equal in every noticeable respect to the DA. No issues with focus with the DA. One small techie point of interest: the Sigma, reported as 30mm focal length, was showing a slightly wider field of view than the DA, reported as 28mm. Go figure.

50mm, close focus.
The sigma is reckoned to be at its best at around 50mm according to the photozone review. For me there was nothing between the shots taken by both lenses - pretty much indistinguishable.

70mm, portrait range
My first sets of the sign at ~ portrait range showed up what seems to be a major distinction between the lenses however when I redid the shots most of the difference disappeared. Operator error! More specifically, the manual focus on the sigma is only ~ 60deg rotation: much more sensitive and much twitchier than the DA, which for me has precise MF. Should've just used AF! Pic wise for me the DA still showed slightly better contrast and resolution in spite of the flatter, duller light second time round. Both were good in respect of colour rendition and no fringing or halo on the lettering.


100mm, portrait
Also at portrait range, this shot also showed the Sigma lagging. I also reshot these to check, using AF second time round, but in this case there was no change. Wide open the sigmas' rendering of the owl is significantly softer. The resolution from the two lenses converged stopping down to f11. Bokeh: nothing to choose between the lenses for me, both pretty good, smooth, no CA fringing of background highlights.


125mm/135mm, not quite infinity focus
Side by side the images from the DA were slightly sharper, but it was only a slight difference. One point the sigma scored on: the DA was clearly showing more red-green fringing on shadow lines.


The last "test" was shooting some jpg's in auto mode to compare out of camera images. The outdoor shots on a bright sunny day proved to be very similar. Mostly the K5 used the same settings with both lenses, though there were a few discrepancies. One difference was the Sigma pics were slightly underexposed (~ 1/2 stop) relative to the DA pics, and the histograms of the latter were usually displaying higher luminance values across the graph. jpg sizes were mostly the same.
Overall between the two: the DA18-135mm tends to be slightly better wide open at all times with distinctly better contrast and has much better manual focus (if you use it). However the Sigma more than keeps up at most focal lengths, certainy with resized images I would say the the results from the two lenses are mostly equal. It has comfortably met my "good enough" benchmark.
The DA18-135mm is given a rating of 8.5/10 in the full PF review, which I would not presume to argue with, indeed it seems pretty spot on to me. I would give the Sigma overeall just a slightly less 8/10. It was pretty much equal through the wide angle to standard range, and only most noticeably inferior with closer focus as the focal length increased. If you are looking for a kit lens replacement and can acquire the Sigma for the sort of price I did, you can be happy.
Senior Member

Registered: August, 2010
Location: Leeds
Posts: 152
Lens Review Date: January 7, 2012 I can recommend this lens: Yes | Price: $135.00 | Rating: 8 

Pros: Price, range, quality
Cons: Vignetting, distortion, resistance to flare could be better.
Aberrations: 7    Handling: 8    Value: 10   

I had been looking for a 28-105 lens, thinking I wouldn't be able to get a 18-105 (or 18-125) for less than 100. Thus, this seemed to be too good to be true. As it happens, it seems I just got a great bargain.

I have tried and owned a fair few of the 28-105 lenses, but for various reasons ultimately wasn't happy with any of them. Over all, I have been very happy with this lens.

For a more detailed review, confirming the quality of the lens, see

Seems to me to be a better buy than the pentax 18-135. (Based on reviews - and price - I haven't used the Pentax.)

I still thinking this is a very good lens, and certainly worth the money, but I would say that the resistance to flare could be better. For this reason I have dropped my rating from 9 to 8.
Senior Member

Registered: April, 2011
Location: Melbourne
Posts: 109
Lens Review Date: October 9, 2011 I can recommend this lens: Yes | Price: $195.00 | Rating: 8 

Pros: Price, sharpness, size, light weight
Cons: Slow, distortion.
Sharpness: 9    Aberrations: 9    Bokeh: 6    Handling: 8    Value: 10   

As I think everyone has already said, for the price this lens is brilliant!

I bought it new with my *ist DS as an upgrade from the standard kit lens and used it solidly for about 6 years.

Its a great lens for anyone starting out in photography. Its small, sharp, light and has a very useful zoom range.

The only thing I may fault is the rather large amount of distortion at both ends of the zoom range.
Inactive Account

Registered: November, 2008
Location: Trabzon/Turkey
Posts: 1,010
Lens Review Date: July 16, 2011 I can recommend this lens: Yes | Price: None indicated | Rating: 9 

Pros: Lightweight, Small, Cheap, 1:4 Macro
Cons: None

I hate the word "bang for the buck", but this lens is really a mega bang for the buck, it has almost a DA16-45 quality, if I rate 16-45 as 9, this lens well deserves a 8.5/10. Colors are good, if you want a very good also very affordable&lightweight walk around lens, this is it. Attaching two direct from camera jpegs, so you can download & decide yourself.

Senior Member

Registered: July, 2009
Location: High Desert, California
Posts: 231
Lens Review Date: May 5, 2011 I can recommend this lens: Yes | Price: $140.00 | Rating: 7 

Pros: Solid build, good color and sharpness if it's a good sample
Cons: QC Issues explained below

This review is for the older, Non-OS, Non-HSM, version of this lens. Based on the generally favorable review of this lens on Photozone, I went and bought this lens off ebay as a kit replacement for my K100D which I meant to to pass along to a budding newbie photographer. And by all appearances the lens received was clean, in very fine shape, and seemed well built. However optically, my copy had one bad problem. The wider the angle, the more open the aperture, the left side of the image was consistently soft and/or out of focus. In fact viewing an image from left to right, the image got progressively sharper, from poor to very good. Not a problem I could adjust for even with my K5. I take this to be a QC issue rather than a defect in design. Ignoring this problem for the moment and just looking at the more than decent rest of the image, you could see where a good copy of this lens could be quite nice for walking around. And for what it's worth the AF was fairly quick and sure. So for anyone considering the older version of this lens - ATT they sell for around $150, often less and if it's a for-certain good copy of this lens I think it would be a real bargain (one should remember that even a good copy will have the usual compromises typical in a lens with this broad a focal range). However the cost is steep enough that a copy with the problem I experienced is a real disappointment and it's not really worth having it serviced. So I would be very reluctant to buy a copy of this lens sight unseen. And since it seems to be a QC issue, even a new-old-stock copy is no guarantee.
Forum Member

Registered: August, 2008
Location: San Jose, CA
Posts: 52
Lens Review Date: December 7, 2010 I can recommend this lens: Yes | Price: $160.00 | Rating: 9 

Pros: Lightweight, very good quality with good range
Cons: none

I won the lens in an ebay auction and found the range to be very suitable for outdoor purposes. The colors, contrast and sharpness were very good outdoors. Indoors I did not find the contrast/ sharpness to be that good which I believe came from my K10D ( I find less sharpness with Tamron 28-75mm indoors for same apertures with my k10D). If you can find it cheap enough, it is very well worth it. I replaced it with tamron 18-250mm and in the same common range, sigma is defintely very good
Focus speed was in general okay
Senior Member

Registered: December, 2008
Location: Minneapolis
Posts: 210
Lens Review Date: May 2, 2009 I can recommend this lens: Yes | Price: $160.00 | Rating: 9 

Pros: Zoom range, inexpensive, lightweight, good IQ
Cons: Vignetting, distortion, not super sharp

This lens is lighter and smaller than other superzooms, but the IQ is still quite good. The convenience of a simple one-lens kit is an enormous advantage in many situations. The lens is an incredible value for the money.

Distortion: modest distortion at the short end; probably only noticeable if you are photographing things with straight lines in the outer portions of the frame.

  • at 18mm, stop down to f/11-f/16 or occasionally more to get really perfect corners
  • at 21mm, f/5.6-f/6.7 is sufficient
  • at 30mm, f/4.5-f/5.6
  • at 50mm, f/5.6-f/6.7
  • at 70mm, f/8-f/11
  • at 125mm, f/11-f/16 or perhaps more
  • Summary: In the middle of the zoom range, vignetting is no problem, but at the short end and near the long end it may require some workarounds. Vignetting is somewhat but not dramatically worse than my DA 18-250.
Senior Member

Registered: December, 2007
Location: Perth Australia
Posts: 293
Lens Review Date: December 5, 2008 I can recommend this lens: Yes | Price: $170.00 | Rating: 9 

Pros: Light. Very good resolving power on K20D.
Cons: DC (APS) only.

Perfect travel lens for my K20.
Minimal distortion at 18mm.
No sign of PF at any length.
Extraordinary value for money.
New Member

Registered: November, 2008
Location: Brisbane, Queensland, Australia
Posts: 10
Lens Review Date: November 29, 2008 I can recommend this lens: Yes | Price: None indicated | Rating: 8 

Pros: Good general purpose, walk around lens
Cons: For the price, and how I use it, none really

The lens came with the camera, and for general use I have had no real issues with it. For disclosure, to help you weigh the worthiness of this particular review, I want you to know that this is my first DSLR and I am enjoying using both the K100d and the lens more than any other camera I have owned, so I am a biased reviewer.

If I were to start from scratch, I think I would include this lens, but I would also like a fast 50mm prime, and something longer, like an old Asahi Pentax Takumar 200mm F3.5 m42.

If you were thinking of purchasing this lens it works best in the mid part of its zoom range, with an aperture over 5.6 or 8. However, saying this, I often do not follow my own advice, and I am still happy with most of my results, especially for the places my pictures get used (normal print sizes and the web).
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