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Sigma 18-50mm F2.8-4.5 DC OS HSM

Reviews Views Date of last review
12 47,801 Sun June 17, 2018
Recommended By Average Price Average User Rating
100% of reviewers $183.08 8.58
Sigma 18-50mm F2.8-4.5 DC OS HSM

Sigma 18-50mm F2.8-4.5 DC OS HSM
Sigma 18-50mm F2.8-4.5 DC OS HSM

Product Features
Lens Construction - 16 Elements in 12 Groups
Angle of View - 69.3 - 27.9 degrees
Number of Diaphragm Blades - 7
Minimum Aperture - F22
Minimum Focusing Distance - 30cm/11.8 in.

Technical Details
Brand Name: Sigma
Model: 18-50mm OS HSM
Lens Type: normal
Minimum focal length: 18 millimeters
Maximum focal length: 50 millimeters
Weight: 0.9 pounds
Length: 2.9 inches
Buy Lens: Buy the Sigma 18-50mm F2.8-4.5 DC OS HSM
Price: $199
Mount Type:
Price History:

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Junior Member

Registered: June, 2015
Location: Százhalombatta, Hungary
Posts: 37
Lens Review Date: June 17, 2018 I can recommend this lens: Yes | Price: $215.00 | Rating: 8 

Pros: Silent and quick focusing, internal zoom and focus, colors, OS
Cons: CA on the borders, weight
Sharpness: 8    Aberrations: 8    Bokeh: 7    Handling: 10    Value: 10    Camera Used: Pentax K-5    Autofocus: 10    New Or Used: Used   

After going through and trying a few lenses, I finally came to terms with this one. Found one used for $215 (60.000 HUF) and got it. Though it came without the lens hood, it still worth it.
First and foremost I was looking for a lens, that has:
  • Silent autofocusing
  • Internal zoom and focus
  • Nice colors

I get all of the above with this lens. I was fed up and angry that most lenses for Pentax came with screw drive focusing, which is not only noisy, but pretty damn annoying as well. Not with this one! I had to enable the focusing beep to know I could expose, because it's so silent, you can barely hear some movement going on inside. Handling of the zoom ring can be done with one finder mostly, pretty much like the Pentax 18-55 WR. Turns the same way as well, unlike the 17-50. So that's a big plus to handling. The lens can't creep due to the way it was made: all internal zooming and focusing.

The lens starts at f/2.8 at 18mm so it's pretty sharp by f/5.6. Go all the way to 50mm and it's usable even wide open. Stopping down just a bit improves even more.
This lens is at its' weakest at 18mm and its' strongest at 50mm. At the wide end you can see some chromatic abberations of the red kind, which can be one-click corrected in Lr with the lens' own profile. At high contrast scenarios, such as branches against the sky, I noticed some purple fringing, but nothing serious. Again, easily corrected.
There's some distortion, but that too is easily corrected. What cannot be corrected however is that the lens generally is sharp in the center and gets pretty weak in the corners.

All in all I gave an 8 for sharpness and a 8 for aberrations. Both because although the lens is nice and takes sharp pictures, there are sharper alternatives, such as the Sigma 17-50 f/2.8 EX and the Tamron 17-50 f/2.8. Keep in mind however that both of those lenses cost at least twice as much as this. I still consider this lens a step-up from the KIT lens however. An intermediate between the KIT lens and higher end lenses. Perfect for hobby photography.
The autofocusing is silent and fast. The focusing ring turns during the focusing action, so don't touch it meanwhile. There's no quick-shift either. There's an AF/MF switch just beside the OS switch. Use that, if you need manual override. The ring turns about 45°.

Remember to turn off the in-body SR when using this lens, or turn off the OS of the lens when you use the body's own solution. Whichever you prefer, turn off the other one. It is said that in-lens stabilization is generally better though, you might want to use that.

All in all this lens is a serious step-up from the kit lens handling-wise and I think in quality too. No longer am I looking for another walk-around lens, because this one fills the gap for me.
New Member

Registered: November, 2013
Posts: 1
Lens Review Date: June 19, 2014 I can recommend this lens: Yes | Price: $170.00 | Rating: 10 

Sharpness: 10    Aberrations: 8    Bokeh: 8    Handling: 8    Value: 10    Camera Used: Pentax K5   

First and foremost this lens is brilliant for my needs and the budget I set myself at least.

I had Ł100 ($170) to spend on a walk around lens with a good focal range, reasonably quick with good image quality. This lens fits the bill perfectly! So firstly the focal range of 17-70 is just a brilliant range for walking around it covers landscapes, portraits and everything in-between. It is definitely fast enough for my needs, I do own several primes so if I need to gather more light or have more control over my depth of field I have them on standby but honestly this lens is perfect for most occasions.

As for image quality, it could just be my copy but it is amazingly sharp across the board to be honest, I have used the Tamron 17-50 2.8 and the Sigma is sharper. It is also worth a mention I have also owned the Sigma Sigma 24-70mm f/2.8 EX DG Macro which was also not as sharp and HUGE for it’s focal range. Alright you loose a bit of speed on the long end compared with those two lenses but who cares I shoot a K5 so increasing ISO is no issue as the noise control is brilliant, plus I have ways and means of removing noise.

To touch on some other points. Build quality is good nothing amazing but by no means poor. The general feel and operation of the lens is also very good with a handy lock switch near the mount end. The filter size may annoy some people to be honest at 72mm you could eat your dinner off it. The close focus is very handy indeed, it’s only 1:2.3 but thats enough for a walk round lens in my opinion.

So to sum up an amazing all rounded that is priced right, produces sharp images and is fast enough for most occasions, you could do a lot worse but spend 3 times the money!
Forum Member

Registered: June, 2012
Posts: 80

2 users found this helpful
Lens Review Date: February 2, 2014 I can recommend this lens: Yes | Price: $150.00 | Rating: 9 

Pros: Internal Focus AND Zoom, Optical Stabilization
Cons: AF isn't blazing fast
Sharpness: 8    Aberrations: 8    Bokeh: 8    Handling: 8    Value: 10   

Recently picked this up to replace a failed DA 17-70 (what a big surprise).

I am rather impressed. Too bad it's not currently made. Yes, the 17-50 2.8 is probably a better lens but it's also large and heavy. Not really a walk-around lens. I picked this up in basically new condition from KEH for $150. It was only $200 new! What an amazing value! I honestly wonder if Sigma stopped making these because they were too good for the price.

At 18mm it's sharper than the DA 18-55 at any aperture. The Sigma at 2.8 is sharper than the Pentax at 6.3 and the Pentax is generally considered decent when stopped down. Stop down to 5 or 5.6 it really is impressive. I'd say the equal of the DA 17-70.

At 50 again, it bests the Pentax easily in sharpness. Wide open at 4.5 it's good enough to equal the kit lens at 7.1 and the kit looks pretty good there. The Sigma sharpens up even more from there. The 50 end is really quite good. Again, I don't think the DA 17-70 ($600) was much better at 50 if at all and it got positively soft after that.

UPDATE: More testing at 50 reveals a very sharp lens even wide open on my K-01. Impressive.

A few bokeh tests at 2.8 looked smooth, not busy. The background grass in the shot below could easily have looked busy but doesn't. The nice 7 blade aperture takes care of that quite well it would seem.

CA looks well controlled, at least as good as the DA 18-55. I did see some in high contrast areas toward the edge of the frame in tests at 18mm but nothing significant and it's gone at longer focal lengths. This "value" lens has a surprising 3 aspheric and two SLD elements to control distortion and aberrations. That's not the kind of glass you expect in a kit replacement lens.

From what I have seen so far the colors are saturated and contrasty producing satisfying shots.

In summary, it's faster on both ends than the Pentax kit and sharper all the way around. It has built-in Optical Stabilization which at least in certain tests seemed to do better than the SR in the body. It also has a M/A focus switch on the lens which is really handy if you want to do any focus trapping. The focus motor is very quiet and for an HSM fairly fast even on a K-01. Yes it's a bit larger but not huge and ungainly like a constant 2.8 lens.

Update: A 1/4s shot test with the Sigma OS vs the K-01 SR went to the Sigma by a wide margin. I was shooting a patterned pillow in very low light in my living room. The SR shot looks okay until you look at the Sigma OS shot and see that the fine detail in the cloth was retained - detail completely lost in the SR shot. Don't get me wrong I still love in-body stabilization but the OS built into this lens is impressive and of course fine tuned for this lens design.

I would say this is one of the best values I have seen in a modern lens. No regrets at all so far. A VERY satisfied customer and seeing the other reviews... I'm not alone.

As proof, here are a couple 100% crops taken wide-open at 18mm and 50mm from different camera bodies while I was testing the lens.

Forum Member

Registered: June, 2013
Location: Torino
Posts: 69
Lens Review Date: November 11, 2013 I can recommend this lens: Yes | Price: $265.00 | Rating: 7 

Pros: Sharpness,Blacks,Fast AF-C,not extend
Cons: none
Sharpness: 9    Aberrations: 8    Bokeh: 7    Handling: 7    Value: 7    Autofocus: 8   

this lens was alone in a shop,with the box coverd of dust..I feel that it was what I'm looking for my K30, I would like dealing with f 2.8 without spend the double of the cost of my camera body.So here a hard to find(maybe out of order) lens, I love what it do,great sharpness at any aperture(max aperture f 2.8 till 21mm/22mm f 4.5 at 50 mm),deep blacks, very fast focus expecially if set on AF-C, SR will work great with OS, but my tests say SR alone is enough and quite better(OS OFF).For now work great with my K30 and I love the not extended way to work.THe colours are not the same of Pentax 18/55 WR and to tell the truth this last one seems a better and fast lens
New Member

Registered: July, 2013
Posts: 5
Lens Review Date: October 30, 2013 I can recommend this lens: Yes | Price: $200.00 | Rating: 9 

Pros: Build quality, Internal Zoom and Fokus, quiet AF, stabilized, sharp, Price
Cons: f2.8 @18-22mm, AF Speed

I Like that build quality like an EX Lens and it is a very good alternative to the Kit Lens.
The HSM is very quiet and not very fast, but it's fast enough. OS works well.
Lens is sharp wide open, but only stopped down it's decent sharp.

Only thing, it has no WR.....
Junior Member

Registered: April, 2010
Location: Greater NY area
Posts: 38

1 user found this helpful
Lens Review Date: November 17, 2012 I can recommend this lens: Yes | Price: $99.00 | Rating: 7 

Pros: Hsm,internal focusing
Cons: Flare

Got it from an amazon deal. At $99 it never left my k-x. Was so much better than the DA-L 18-55!
With the K-5 I reach for the 18-135 most of the time when I need a zoom (or I get a DA limited) although:
- sigma is much sharper in the center @ 18mm f2.8 than my Pentax even at f5.6
- sigma get better after f8 at 50mm (Pentax is better @50mm wide open but loses ground at f8)
The Pentax though is lighter, shorter, has a longer reach and is WR.

Overall this is a good landscape lense on the wide end at any aperture and good portrait lens past f/8.
Emperor and Senpai

Registered: June, 2010
Location: Nashville, IN
Posts: 5,928

1 user found this helpful
Lens Review Date: March 10, 2012 I can recommend this lens: Yes | Price: $149.00 | Rating: 9 

Pros: Sharp, decent under lower light, and cheap!
Cons: None I can think of

I bought this lens used, but like new from someone with buyers remorse to replace my kit lens. I can honestly say of what I have no it is my favorite lens, and it stays attached to my camera at the anime conventions I like to shoot at. It is great in the crappy lighting situations I've found myself in while working at the booth in the dealer room, and is a major, but very cheap upgrade to the kit lens. I'd recommend this lens to anyone.
Senior Member

Registered: March, 2011
Location: Houston, Texas
Posts: 112

2 users found this helpful
Lens Review Date: January 22, 2012 I can recommend this lens: Yes | Price: $200.00 | Rating: 10 

Pros: Silent focus, internal zoom, internal focus, price, image stabilization
Cons: Average focus speed, weight, size

What a bargain! One of the true values for any Pentax DSLR. This Sigma provides better than average image quality and is a great upgrade from the kit lens. It is slightly faster at both the wide end and long end than the kit zoom. This Sigma also has a nice quiet auto focus motor with an optical stabilizer. The coolest thing is the internal zoom, which means that the lens doesn't extend when zooming in and out. Had never seen an internal zoom lens priced at $200 before. In fact, I didn't even know that this lens had an internal zoom until I got it. It was a very very very pleasant surprise.

The lens is a little bigger and heavier than I expected for a 2.8-4.5 lens with limited focal range of 18-50mm. The Tamron 17-50 with constant f2.8 is both smaller and lighter. On the other hand, this Sigma does have an internal motor and optical stabilizer (the Tamron doesn't), which somewhat justifies the larger size and heavier weight. The Pentax 18-135 has a more versatile focal range and an internal motor, but is also smaller and lighter than the Sigma 18-50.

Auto focus speed doesn't seem faster than either the kit lens, the Tamron 17-50 or the Sigma 17-50. Out of the four, the Sigma 17-50 might be the fastest, but just barely faster. The Pentax 18-135 is faster than the other four lenses. I don't seem to have any back or front focus issue with this Sigma.

Image quality is better than average, and slightly better than the Pentax 18-135 in my opinion. You can focus about as close as 6-10 inches (guesstimate), depending on the focal length.

Overall, I'm very satisfied with the Sigma 18-50, particularly at the bargain basement price of $200. Recommended.
Veteran Member

Registered: September, 2010
Location: Canberra
Posts: 739
Lens Review Date: July 18, 2011 I can recommend this lens: Yes | Price: $150.00 | Rating: 8 

Pros: HSM is Quiet. Solid build. All internal zoom/focus means stays compact. Improvement over Kit Lens, Faster, Sharper, Price
Cons: Would be nice to have a longer focus range (shorter and longer before infinity)

I'm really starting to like this lens. Its much sharper than the Kit Lens, and compliments my Tamron 28-75mm nicely. The fact they both take 67mm filters is also nice.

The HSM is quiet and fast, and the OS beats SR - I've pushed it to 0.5" and still gotten acceptable images!

This is a 50% Crop taken on a K20D:

Veteran Member

Registered: October, 2009
Location: Texas
Posts: 384

1 user found this helpful
Lens Review Date: July 7, 2011 I can recommend this lens: Yes | Price: $199.00 | Rating: 9 

Pros: Pretty sharp, great walk around lens, Price
Cons: Can't get close too when zoomed out.

I had this lens for a few weeks and I have to say I love it, beats the 18-55mm Pentax kit lens for being wide and captures more in frame and much faster at f/2.8
Only thing is I can't get as close to things without zoom and lose f/2.8 but other then that this lens is great!

I use it to take photos of the fireworks this July.

Pentax 18-55mm vs Sigma 18-50mm
Veteran Member

Registered: March, 2011
Location: Maryland (Right Outside Washington DC)
Posts: 2,902

1 user found this helpful
Lens Review Date: April 12, 2011 I can recommend this lens: Yes | Price: $200.00 | Rating: 8 

Pros: Prices, Descent AF Speed, 18-50 Range, Build Quality, Sharpness Stopped Down
Cons: Not as fast as most 2.8 lenses

Seems to be one of the best value-2-quality AF lenses out there. The build quality is pretty good for a $200.00 piece of glass. For the price, IMHO, I think this is one of the best kit replacement lenses available.

At 18mm you can use this lens opened up @ 2.8, which is a plus - however, it is a tad bit soft. I found that stopped down to 5.6 produces fairly sharp images throughout its range. The only con I have with this lens is that it does not seem as fast as most 2.8 lenses I have in my bag, but other than that, this lens is a winner...
New Member

Registered: February, 2011
Posts: 1

1 user found this helpful
Lens Review Date: February 19, 2011 I can recommend this lens: Yes | Price: $200.00 | Rating: 9 

Pros: internal focus and zoom, build quality, HSM for quiet autofocusing, F2.8 maximum aperture at 18mm
Cons: a bit soft wide open

A good alternative to the kit lens, especially if you bought your DSLR body only.

HSM autofocusing is quiet and fast compared to conventional screw drive. Internal focus and zoom is a great addition to a lens in this price range. Slightly larger aperture than the various kit lenses. Overall build quality feels far superior to the kit lenses that comes with most DSLRs.

Sharpness and image quality is acceptable, especially in this price range. Obviously softer compared to Canon L lenses or Pentax DA* lenses, but this lens is far cheaper as well. Becomes fairly sharp after a couple of stops.

Overall, it's a good lens for the price.
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