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Before I bought this lens I asked many professional photographers what they'd recommend for portrait photography - and 9 times out of 10, this lens was suggested. I wasn't bothered too much about the price as I knew I'd be shopping for a second hand, little used, well looked after lens.
- Focal Length 17-70mm
- Construction 15/12 elements/groups
- Angle of view 72.4º-20.2º (SD format 1.7x crop)
- Max Aperture f/2.8-4.5
- Min Aperture f/22-f/32
- Min focus 20cm/7.9inch
- Max magnification 1:2.3
- Filter size 72mm
- Dimensions 79x82.5mm
- Weight 0.455kg
- Mount Sigma, Canon, Nikon, Pentax, Minolta.
I paid just under £200 for this lens and yes, that sounds pricey, but in all reality it is a bargain for what I was quoted for buying new (around the £300-400 mark!) and really a good lens is priceless - and if you're a photographer it is an investment in your business.
The lens has a matt black finish - before I had any equipment I never understood why it was black, now it makes sense due to touching the camera and lenses so blooming much! It has a metal mount with a white mark on it to indicate where you line up the lens and the camera lens mount. It is a bit of a tight fit on my Canon 1000D but after a few practices of taking it on and off, this is less of an issue.
The image quality is great, but usually at the shorter end of the lens (around 1:4.7-1:3.5 I have found the best results.) Also the closer to the subject, the sharper the result. The lens has AF (auto-focus, which means the lens sets the focus) and MF (manual focus, meaning you set the focus) and you can lock the lens to stop 'lens creep' (where the lens may move down a little - or a lot - messing up the focus you've set on the lens.)
Auto-focus is brilliant on this lens. I think it's one of the better auto-focuses in comparison to other lenses I've used; it's 'quiet' meaning that there is no grain on the photos I take. Depending on your camera settings and subject, there is never any motion blur on this AF. Manual focus is 'okay' and I know I should really be using it, but I find it quite noisy (grainy) and that it causes an awful lot of motion blur - need to figure it out, I suppose!
When photos are enlarged there is little to no pix-elation on photos, which is a refreshing change - think I may be ordering some canvases soon ;)! This lens works best in natural lighting, giving really sharp and clear images and when not enough light gets into the lens it makes pictures look very grainy and dark - this is the case for most lenses, of course, but I have found it to be so much more so with this lens. Although you can get a very good close up image - not quite a macro lens, not technically anyway, but good enough for shots of small objects with a distorted background.
With the flash - I'd say it would be wise to invest in some off-camera flash equipment while using this lens. My flash is just a small, pop-up flash and while it reaches the end of the lens, it sometimes doesn't always bounce where I want it too. A flash gun and diffuser might be another way to go to get best results with a flash.
Without the flash - I think you'll get the best results in natural light, without the flash. But that's true of most lenses. However, for this one, I've found it very much the case. Until you can afford the flash gun and diffuser, stick with this method for best results ;).
I've also found this is a sturdy lens, it feels very heavy, and being made out of glass rather than plastic this would account for the weight difference and the weight gives you some reassurance that you're getting a 'good' lens. It requires no batteries ;) (I know that's an obvious point but DooYoo have put a 'battery life' attribute on here.)
Overall I give this lens a 5/5 because I really feel that for the price, it's a bargain. If you can, find a decent second hand lens, it's what I did and to be honest I think for what I paid I got a bargain - and some really beautiful photos! With a flash gun and diffuser (I have a birthday and Christmas coming up!) I expect really great results no matter the lighting situation, but this lens works best in natural light situations and doesn't perform too well in low light conditions.
When I first bought my Sigma 17-70 OS HSM DC for my Nikon D80 I couldn't wait to try it out at a wedding. The 2.8 aperture promised easy shooting at low light and I was expecting it to blow my plasticy 18-55 kit lens out of the water.
The first thing I do with all my lenses is check accuracy of focus. Unfortunately, although the autofocus was super fast and silent (the HSM motor really does it's job) the lens consistantly back focused for me, that is the subject in the focus sensor was slightly out and the area behind it was sharp. Sigma were willing to fix this for me but required my camera too for a 3 week turnaround. If your buying second hand and you need this be aware that it may cost up to £50 to do this, beware if buying second hand without a returns policy.
The other misleading stat on this lens is the 2.8 maximum aperture. Yes it will shoot at f2.8 ( a whole stop more than f4) but it quickly starts to stop down as you go through the zoom range, by 20mm you're at f3.2, by 24 you're at f3.5. As you can see the advantage over much cheaper kit lenses is quickly lost.
I found that wide open at 17mm this lens was so soft it was almost unusable. I see little point in paying a premium for an f2.8 lens if it must be stopped down to f4 before it starts to get sharp.
With all that said there are some great positives to this lens....
First off, the OS (Optical Stabilisation is Sigma's version of VR) is exceptional, I could shoot hand held shots at 1/4 of a second and the anti shake trickery kept everything sharp and blur free. This really is a revelation, not quite as quiet as my VR lenses but very effective.
Secondly this lens is big. Big and impressive, with a 72mm filter thread and a reversible flower petal lens hood it looks intimidating and very professional indeed. This does mean that it looks a little odd matched to a small form DX camera but with a Full frame or DX with battery grip it really look the part.
Overall I would have been thrilled with this lens if the autofocus had worked better with my D80, idf you are buying new from a shop, try before you buy and keep trying till you get an accurate copy. When I used manual focus the images were crisp and sharp when at f4 or more.
If only that focus worked a little better.
I had, but since sold my copy (Pentax mount), but not because of its lack of quality.
This lens has a great zoom range in crop sensors. You will notice that 1mm to your 18mm from the kit lens. And at 70mm max, it helps to get a bit more detail out of your subjects and also makes for a better portrait lens (headshots).
Focus wise, its not particularly fast on a K10D, but good enough. There is a newer version with Sigma's HSM motor built in which will be at least quieter, if not faster. What is really great about its focus is how close it focuses. It is not macro, but it is very close focus.
The build quality is good, but as you use it, it actually looks better than it really is. The coating on the body of the lens looks and feels good, but rubs of and actually got my camera bag dirty.
The focusing and zoom rings feel good in operation, but not super smooth. Perfectly acceptable for this price range.
One of the pluses attributed to this lens is the F2.8 aperture. I found it inconsequential. Its only avaiable at 17mm, so not really a great feature. F2.8 at 70mm would be really cool for portraits, but then it would be whole different lens, with a different price tag.
The picture quality is very good throughout, but not that you do notice a slight drop in sharpness at the widest and at F2.8.
I bought this lens half a year ago(new). I had problem with it at the beginning. It had back focus (It focused after the "target"). I sent it back with my digital camera to Sigma and they adjusted it for free(I paid postage one way). After two weeks waiting I started shooting. Now, after few thousand pictures taken I can say few things about yhis lens.
- optical quality - it`s sharp(very sharp above f4.5-5.6). Much sharper than my Konica-Minolta 18-70 mm f/3.5-5.6 DT(It was my KIT lens),
- build quality - very good material used by Sigma. Zoom ring works very good and focus is fairly quiet and accurate to cope with most uses. There`s on/off switch and zoom lock wchich I didn`t use(doesn`t extends when camera points down).
- macro mode - it focuses from about 10cm - great!
- value for money - not cheap but worth price,
- starts from 17mm - it`s only one mm wider than my old minolta 18-70 kit but I can see the difference.
- vignetting ("dark corners") can be noticeable at 17mm @F2.8,
- barrel distortion at 17mm especially if shooting straight lines.
I think it`s a very good lens. Much more better than my old minolta 18-70 kit lens. I would recommmend it instead kit lens. It`s a very good walk-around glass. I would buy it one more time but without problems with back focus :)
If you want to read more reviews about this lens: