did not fit my sony camera

Excellent lens, very sharp even wide open. Only minus would be size, compared to Pentax lenses but f1/8 is nice to have. Waiting for full frame from Pentax now :)

I already own and use a heck of a lot Nikon's pro 17-35mm D lens, which is only 1.5 stops slower and whose quality is not even bettered by Nikon's own 20mm f2.8 D. So, why should I bother with this Sigma?

Firstly, the 17-35mm has already been repaired/refurbished once and is old. And very heavy. I'm semi-pro and where I've had a kit that extends down to my superb 24-70mm f2.8 (another Sigma, the HSM model), I used to slip in my pocket an even older Tamron 17mm f3.5, which uses the old adaptall 2 system, and is manual focus only. A replacement with a newer, better one than mine is up to £200. The quality of the Tamron is rubbish wider than f5.6, but then on, is as good as the Nikkor 17-35mm.

So, this Sigma 20mm f1.8, which I bought secondhand for around half the normal new price is also a bit rubbish at f1.8, particularly contrast. By f2.8 it's better and f4 is good (see my image at the top of the Amazon page) and from then on, is contrasty and sharp, not better than the 17-35mm, but then, almost nothing else is! Another image I've added was taken on DX Nikon D7000 handheld at night, at f1.8. On the DX, it's equivalent to a 30mm f1.8; still a very useful spec.

Unlike the lead-weight of my all metal tank-proof 17-35, the Sigma is plastic, apart from the metal mount and glass elements, of course. This makes it a lot lighter, though its dimensions are a lot bigger than my little Tamron 17mm f3.5. The 20mm f1.8 takes giant 82mm filters, which are costly and its decent lenshood has some effect reducing stray light and flare, but with that wide frontal area it is rather prone to ghosting and the multicoating is in another, lower league than the Nikon. However, careful placing of the sun behind trees and such and it does OK and stopping down helps, too.

The auto-focussing is good and fairly quiet and accurate (some Sigma's back-focus, but mine's fine) but it's too old to include their hypersonic drive system (HSM). Having said that, the barrel does not rotate and the lens elements are light so

I already own and use a heck of a lot Nikon's pro 17-35mm D lens, which is only 1.5 stops slower and whose quality is not even bettered by Nikon's own 20mm f2.8 D. So, why should I bother with this Sigma?Firstly, the 17-35mm has already been repaired/refurbished once and is old. And very heavy. I'm semi-pro and where I've had a kit that extends down to my superb 24-70mm f2.8 (another Sigma, the HSM model), I used to slip in my pocket an even older Tamron 17mm f3.5, which uses the old adaptall 2 system, and is manual focus only. A replacement with a newer, better one than mine is up to £200. The quality of the Tamron is rubbish wider than f5.6, but then on, is as good as the Nikkor 17-35mm.So, this Sigma 20mm f1.8, which I bought secondhand for around half the normal new price is also a bit rubbish at f1.8, particularly contrast. By f2.8 it's better and f4 is good (see my image at the top of the Amazon page) and from then on, is contrasty and sharp, not better than the 17-35mm, but then, almost nothing else is! Another image I've added was taken on DX Nikon D7000 handheld at night, at f1.8. On the DX, it's equivalent to a 30mm f1.8; still a very useful spec.Unlike the lead-weight of my all metal tank-proof 17-35, the Sigma is plastic, apart from the metal mount and glass elements, of course. This makes it a lot lighter, though its dimensions are a lot bigger than my little Tamron 17mm f3.5. The 20mm f1.8 takes giant 82mm filters, which are costly and its decent lenshood has some effect reducing stray light and flare, but with that wide frontal area it is rather prone to ghosting and the multicoating is in another, lower league than the Nikon. However, careful placing of the sun behind trees and such and it does OK and stopping down helps, too.The auto-focussing is good and fairly quiet and accurate (some Sigma's back-focus, but mine's fine) but it's too old to include their hypersonic drive system (HSM). Having said that, the barrel does not rotate and the lens elements are light so they don't need much time or e

I bought this for use on my D3. It works pretty much as the reviews say (elsewhere). at f1.8 you do get a lot of vignetting but at f4 and higher its not a problem. Its all fixed very well with the lens profiles on Lightroom 3. Its sharp. I reckon just about as good as my Nikon 24-70. It a good buy if you want a wider angle lens for a full frame DSLR without going to the expense od something like the Nikon 14-24 at £1300. I worked out that the 20mm is only a shade off the angle i got using a 12-24 on my old D200, so its wide!

I'm glad i bought it, but keep in mind the lens did come out a good few years ago and it was originally designed for film, thus the edge fall off. I bought it under the "new and used" for £250. I would suggest the new price above is far too expensive for what it is, you should get a good second hand one for around £250 - £300

I'm only rating it a three as a Nikon 14 - 24 would get a 5, and its no where near that quality of lens. But as i said the picture quality is fine and that from someone who uses pro lenses.

I bought this for use on my D3. It works pretty much as the reviews say (elsewhere). at f1.8 you do get a lot of vignetting but at f4 and higher its not a problem. Its all fixed very well with the lens profiles on Lightroom 3. Its sharp. I reckon just about as good as my Nikon 24-70. It a good buy if you want a wider angle lens for a full frame DSLR without going to the expense od something like the Nikon 14-24 at £1300. I worked out that the 20mm is only a shade off the angle i got using a 12-24 on my old D200, so its wide!I'm glad i bought it, but keep in mind the lens did come out a good few years ago and it was originally designed for film, thus the edge fall off. I bought it under the "new and used" for £250. I would suggest the new price above is far too expensive for what it is, you should get a good second hand one for around £250 - £300I'm only rating it a three as a Nikon 14 - 24 would get a 5, and its no where near that quality of lens. But as i said the picture quality is fine and that from someone who uses pro lenses.

I have one of these and I'm very happy with it. It's an ex lens and as such it's full frame compatible however it remains useable on an APS-C digital SLR camera on which it'll be the equivalent of 32mm assuming a "crop" factor of x1.6.

The lens lacks HSM however the focus ring can be pushed forward thus avoiding accidental damage when in AF mode. I think that this is a nice touch but that the lens would be even better with HSM.

Whilst the widest aperture setting of f1.8 doesn't produce the sharpest of images it may prove useful for low light or creative DOF shots and as this lens is possibly best suited for landscape use at narrower apertures I think that a little softness at f1.8 shouldn't detract from the usability of the lens at all. In my view a maximum aperture of f1.8 is nice to have but isn't or shouldn't be the main reason for buying the lens.

All in all I'm very happy with this lens, HSM would be nice, but it's still a very nice and useable lens without it.

I have one of these and I'm very happy with it. It's an ex lens and as such it's full frame compatible however it remains useable on an APS-C digital SLR camera on which it'll be the equivalent of 32mm assuming a "crop" factor of x1.6.The lens lacks HSM however the focus ring can be pushed forward thus avoiding accidental damage when in AF mode. I think that this is a nice touch but that the lens would be even better with HSM.Whilst the widest aperture setting of f1.8 doesn't produce the sharpest of images it may prove useful for low light or creative DOF shots and as this lens is possibly best suited for landscape use at narrower apertures I think that a little softness at f1.8 shouldn't detract from the usability of the lens at all. In my view a maximum aperture of f1.8 is nice to have but isn't or shouldn't be the main reason for buying the lens.All in all I'm very happy with this lens, HSM would be nice, but it's still a very nice and useable lens without it.