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Here's a brief look at the Sigma 10-20mm F/4-5.6 EX DC zoom lens.  Scroll down for the review.


Box contents

Front and rear caps, hood, nice softcase and users manual.


About $479

Build quality


Additional information

See another model with this focal length, the Sigma 10-20mm F/3.5 with HSM focusing

Specifications below


Optical configuration

14 elements in 10 groups

Angle of view



6 blades, straight

Full frame and APS-C

APS-C only, 35mm equivalent, 15-30mm.  Will work on full frame, but vignettes massively at 10-14mm.  Turn on APS-C size capt. for good pictures.

Depth of field and focus scales?

Focus distance scale only

Minimum focus, image plane to subject

9.5"  (240mm)

Minimum focus, end of lens barrel to subject

4.4"  (112mm)

Hard stop at infinity focus?


Length changes when focusing?


Focus ring turns in AF?


Filter size


Filter ring rotates?


Distance encoder?


Max magnification


Min. F/stop


Sony teleconverter compatible?


Length changes when zooming?


Dimensions W x L (my measurements)

3.27" x 3.2"   83mm x 81mm 

Maximum  extended length (my measurements)

3.35"  (85mm)                                                      

Weight bare (my scale)

12.7oz  (362g)  13.7oz (390g) with caps

Requisite product shots.

Here's the box and contents

Front with plastic petal hood

Rear shot, look at warped aperture

Side shot fully extended

Front view, that's not dust you see, it's Sigma's sparkly dirt-look finish

Sigma MTF screen grab, incomplete, but this is all they give.

X-ray view

The Sony A700 was used for this review.  For a better understanding of my review methods and terminology, go here.
The Sigma 10-20mm F/4-5.6 EX DC is currently the widest of the super-wide angle zooms available for your Sony APS-C sensor camera, and isn't designed to be used on full frame/film cameras.  The lens is finished in the standard Sigma sparkly dirt-look black which I hate, however, quality is good, with a nice fit and finish.  It also has rubber ribbed grip areas around the zoom and focus rings, a metal mount, and a distance scale, which you'll need, see below.  The lens says made in Japan.  This lens is identical in size, weight and close focusing distance to the Sony 11-18mm, but they are optically much different.  Sigma claims they use three aspherical, and three "SLD" elements in the construction of this lens.  Note; don't set this lens mount side down at 10mm, the rear element will touch the surface and wobble around.
Zoom control is nice and smooth and the barrel extends out (clockwise) another 4mm at full extension.  The focal length numbers come at; 10mm, 12mm, 14mm, 17mm and 20mm.  Oddly enough, my lens won't register 14mm in the EXIF data, all other numbers show up, even in-between lengths (except 19mm), but 14mm is written on the barrel, so it should show, this is the same missing data as the Sony 11-18mm.  There's a lot of room between each number, so you could shoot different scenes at the same length as it appears in the data, but it may look substantially closer, or farther away, that's in the design, they don't put enough internal length sensor contacts to mark every single change of movement.  Other lenses are like this too, it's not a defect, but maybe the missing 14mm is.
Auto-focusing is troublesome, typical for Sigma.  At 10mm, I have to set the focus ring to the 1 meter mark, where everything from about 6' or 2m will be in sharp focus.  Auto-focus will choose something past infinity, and everything will be out of focus. At 20mm, the infinity mark is fine.  Manually focusing is easy, as you have 1/5 turn from close-in to infinity, which is plenty of rotation, and the focus ring is smooth and easy to turn.  The closest focusing distance from lens barrel to subject is 4.4" or 112mm.  The problem above effects my lens.  Due to the obvious lack of quality control, another copy may, or may not have this problem.  I've had several Sigma lenses over the years, and they've all had focusing issues.


Aperture/focal length guide for the Sigma 10-20mm F/4-5.6.  This lens has overlapping numbers, depending on tiny movements of the zoom ring, this is quite common.  Look below for guide.  Also, this lens did not register 14mm in the EXIF data, which is the same as the Sony 11-18mm.  So why do they put 14mm on the barrel?  Also no 19mm, but that's no problem.


Maximum aperture







11mm - 13mm

15mm - 16mm

17mm - 20mm

Flare and ghosting.  Lens flare is very strong at all focal lengths with the aperture wide open.  If the sun is in the image, or just outside, you'll have some rough looking shots, depending on the scene.  One stop down helps tremendously.  See small sample of flare below, at full size it looks terrible.  The Sigma is much worse than the Sony 11-18mm in this department.  Good news though; if you shoot at F/8, things look much better, and the sun doesn't cause any real problems, other than a couple of small ghosts.  Overall, ghosting is well controlled, and better than the Sony 11-18mm.  This lens comes with a nice plastic petal type hood, but it doesn't help the situation described here.  Use your hand when the sun is close to the image periphery, which will eliminate the flare, but only when the sun is actually outside the image.
This lens is multi-coated and looks very similar to the Sony 11-18mm front. 
Filter use;  no vignetting when using normal filters. 
Filter size.  77mm.  Sony lenses using this size are: 70-200mm G, CZ 24-70mm, and CZ 135mm F/1.8
Coma.  Light wide open at 10mm.  Stopped down, no problems.  This isn't something to worry about, it's only in the corners.  See crops below.
Color.  Looks the same as Sony lenses.
Lateral color fringing is about average with the Sigma 10-20mm, It shows up at all apertures and all focal lengths.  Stopping down doesn't help, you'll have to live with it or remove it with your imaging software.  It's mostly magenta/cyan along the sides of the image, a little better control here than the Sony 11-18mm.

Moderate barrel distortion, 10mm

Moderate pincushion distortion at 20mm.

Barrel and pincushion distortion.
  The distortion at 10mm-11mm is odd mustache type, hard to correct in post processing.  There is no flat point in the zoom range, and pincushion starts around 13mm.  The Sony 11-18mm is better at controlling distortion.  In landscape shots, this distortion rarely shows up unless you're shooting straight lines near the image edges.  A workaround for the mustache distortion is to zoom out to 11-12mm for architectural type shots. 

Lens Bokeh.  The Sigma 10-20mm F/4-5.6 is just so-so to harsh in this department.  Generally, everything is in focus less than 15' (4.5m) and beyond, so background blur isn't something I'd worry about with this lens.  See crops below.

light fall-off, directly below, looks strong at 10mm and F/4, stopping down to F/5.6 helps, but at F/11 there is still a small amount.  You'll find some too at 20mm, F/5.6.  Check out the sample below and see how light fall-off looks in a real picture from this lens.  The Sony 11-18mm is much better at controlling light fall-off or corner shading.

    10mm @ F/4

  10mm @ F/5.6



    20mm @ F/5.6

   20mm @ F/8




Random shots below. 


    10mm @ F/4 Light fall-off

  10mm @ F/4 massive flare



    10mm @ F/4 bokeh

  10mm @ F/5.6 bokeh



    20mm @ F/5.6 bokeh

  20mm @ F/8 bokeh



    10mm @ F/4 coma

  10mm @ F/5.6 coma



The left shot above shows light fall-off at F/4, 10mm, which really isn't noticeable with a real picture, it's quite different from the test shots above.  This shows you why you shouldn't worry about stuff like this.  The right shot is massive flare, F/4 at 10mm.  It's bad here (and looks worse enlarged) as I said above, it'll ruin your shot.  Close the aperture one stop (F/5.6) and things look much better, and F/8 looks pretty good at all focal lengths.  This flare is visible in most sun shots, though sometimes a busy background can hide it.  The Sony 11-18 has this also at F/4.5, but it isn't nearly as bad as the Sigma.  There used to be filters that did the same thing as you see in the flare shot, and you paid good money for them.  Some people may actually like this affect.  Good news for ghosting, control is good, and much better than the Sony 11-18mm.  There's a faint red ring that can be seen at the corners when the sun is close to the center of the image, just barely visible in the top right shot.  If you don't like to take pictures with the sun in the image, don't worry about all this. 
Bokeh shots in the middle.  This lens isn't for getting creamy smooth backgrounds, just about everything is sharp in a real picture, so don't worry about the rather harsh looking background blur.  You can occasionally make out the six bladed aperture, even wide open, again, no big deal on a super-wide angle lens.
Coma, bottom row.  Light at 10mm and F/4.  No problems stopped down.
Corner softness at 10mm.  See cropped images below.

    10mm @ F/4

  10mm @ F/5.6



    10mm @ F/8

  10mm @ F/11




20mm corners


    20mm @ F/5.6

  20mm @ F/8



The 10mm corners are soft wide open, two stops down makes them nice and sharp.  At 20mm, one stop down and everything is sharp.  This lens is sharper in the corners at the wide end than the Sony 11-18mm.  If you're using this lens at 10mm for its intended purpose, you won't care about the corners anyway.  If you're taking pictures of your home or architectural type shots, and you want everything super sharp, stop down to F/8 but not F/11, where softening of the image occurs due to diffraction.  For indoors, use a tripod if you can't get the shutter speeds you require for hand-held use.
Center samples at 10mm next.

    10mm @ F/4

  10mm @ F/5.6




20mm centers


    20mm @ F/5.6

  20mm @ F/8



Look at the boring pictures above.  This isn't the way to shoot this lens, but it shows you real results.  Feel free to shoot at F/4-8 with this lens at any focal length.    Leave F/11 alone, it's a little soft due to diffraction.
Examples of the differences in focal lengths at wide angle below.

11mm (16.5mm equivalent)

10mm (15mm equivalent)

Look at the difference in area covered going from 11mm to 10mm.  It's noticeable here, but you probably wouldn't really see it unless compared side-by-side.
Check out the close focus shot.

Below, check out the sample, cropped to reduce size, and click (144kb) to see image.  The sample shot was taken with the Sony A700 12.2MP camera.  The subject is a standard US stamp, 1"x 3/4" or 25.4mm x 19mm.  Also, note the macro shot was taken as close to the subject as focusing allowed; In this case, 4.4" or 112mm, measured from the front of the lens barrel to the subject, the same as the Sony 11-18mm.
This lens has a small reproduction size at 0.15x.  It isn't meant to be a good close up lens, so don't use it for this.  The image below was taken at F/8, but F/5.6 was similar.

100% crop, click for larger image F/8


The Sigma 10-20mm F/4-5.6 is currently the widest of the super-wide angle zooms you can buy for your Sony APS-C sensor camera that accepts regular filters, that's important, because the Sigma 8-16mm will not, so you can't use a cloud saving graduated neutral density filter.  Cost wise; it's less than the Sony 11-18mm by a good chunk of change.  If the widest you've ever shot is 18mm, you'll be in for a surprise when looking at 10mm.  This also brings up some problems, see the last paragraph.   
The Sigma 10-20mm F/4-5.6 super wide angle lens turned in a very good performance, although it's not perfect.  Flare/veiling glare is harsh wide open at all focal lengths, and the focusing issues as mentioned in the introduction.  There are some good things too; ghosting is well controlled, the corners are sharp at one or two stops down; and at 10mm, you'll have plenty of room to pack some fun in the image.  This lens is very good if you shoot at F/8-11; you won't need to worry about focusing issues, because you'll have a huge DOF, and flare is mostly gone at F/8 as I stated earlier.  Note: there could be sample variations, so my copy may not be indicative of all.  If you don't like taking pictures with the sun in the image, don't worry about the flare issue.
To give you an idea about how much this lens will cover, at 10mm or 15mm in 35mm terms, you can get an entire normal-sized bedroom in the frame, from wall to wall, standing at the door.  The lens at 10mm covers a lot of real estate.  Unless used correctly, most people will not enjoy their results with this lens.  Problematic areas include, getting your shoes in the shot, I've done it, getting way too much ground or sky in the image, and winding up with pathetic tiny unrecognizable objects strewn across the middle of the frame, because you were too far away from your subject and didn't understand the proper use of the lens, I've done all of those things.  Try some forced perspective type shots, like getting the camera square in the middle of the action or object of interest, that makes it much more interesting. 
This super wide angle lens is also good for taking pictures of rooms or areas where you can't back off enough with a normal lens, this is also called "getting it all in" and sometimes you just feel the need to do it, but is shunned by many photographers.  Used in this way walls tend to want to tilt hard over from the lens not being exactly level (keystone), and things near the periphery look elongated, but some of that can be corrected in imaging software.  
Don't forget to check out the newer Sigma 10-20mm F/3.5 HSM, if you have the extra money, I'd get this lens.