I will try to keep this review fairly brief as there are several more reviews and much discussion about this lens elsewhere (see this discussion: http://photography-on-the.net/forum/showthread.php?t=934592). I have put the good/bad points and a conclusion at the top for easy access.
Some pictures of the lens with my 7d attached (yes it was raining!):
- Good image quality wide open, amazing when stopped down even just 1-2 3rds of a stop.
- Takes 1x and 2x teleconverters (great IQ with 1.4x)
- Good price
- Build Quality is good (apart from lens hood)
- Very good image stabilisation
- Reliability (a massive negative for some users, not so much for others)
- AF maybe not as great as it could be (although it’s still good)
This lens is very sharp, and can be amazing when it works and compared to competing lenses is VERY good value. However the price you pay is the risk of having to send it back for repair if the electrics fail.
Basically if you want an f/2.8 zoom in this range then there is no other choice. If you want a new lens capable of 300mm f/2.8 or 400mm f/4 for under £3000-£4000 then this is the only option. Many reports of serious autofocus failure and image stabilisation problems mean that this lens is probably unsuitable for anyone that values reliability above all else.
I have been looking for a wildlife lens that consistently gives me images that I’m happy with for a while now and this introduction is basically just me justifying (to myself as much as anyone) why I need/want this lens.
With the prospect of spending a whole year working very closely with such enigmatic animals as Meerkats looming ahead of me I decided that I wanted the best image quality that I could afford.
With the opportunity to spend that much time being able to watch my subjects and hopefully witness some interesting behaviours I think that I would be very unhappy if I came away with photos that I didn’t feel were up to scratch. My thinking was that as I’m going to have so many chances to work on compositions, see cool behaviour and wait for the best lighting then equipment was the most likely thing to let me down in terms of image quality.
I have owned the Sigma 120-400mm and the Canon 100-400mm and whilst the Canon was much sharper I still found it hard to get images that I was happy with in anything other than great light. My other options were the Canon 300mm f/4 IS, Canon 400mm f/5.6 and Canon 70-200 f/2.8 but in the end I decided the 120-300mm plus 1.4 teleconverter would give me the most flexibility without compromising speed or image quality.
Most people consider image quality to be the most important aspect of a particular lens and the 120-300mm doesn’t disappoint. When stopped down just a tiny bit it’s about as sharp as you can get even with the 1.4x teleconverter!
I can’t comment on how it works with the 2x teleconverter as I’ve never used it however I have seen some sharp pictures taken with this combination. I also can’t comment on the edge image sharpness with a full frame camera as my 7d is a 1.6x crop body.
Overall I’m very very happy with the image quality that this lens gives.
Here are some 100% crops (print screen at 1:1 view in lightroom) to show the drastic effect on sharpness stopping down by just 1/3rd of a stop has. Pictures taken on a tripod with a remote release but it was very grey, raining a bit and very windy so not the most scientific test and I just picked the sharpest from about 10 shots. All shots unedited SOOC raw and imported into lightroom.
And with the Sigma 1.4x teleconverter (I moved the tripod back to get the same framing):
And the uncropped image to give some perspective:
The build quality on the body of this lens is very good, it feels solidly built, nothing wobbles and it has the new Sigma finish which is much better than the old finish which got dirty quickly, was difficult to clean and chipped easily. The only minor issue is the plastic lens hood (which some complain is a bit flimsy but I think is fine) was quite loose fitting, didn’t really click into place properly and was liable to fall off. However I sorted this with a couple of carefully placed bits of electrical tape.
This lens is quite a heavy lens (~3KG) but I have no problem handholding it however I have invested in a monopod for a bit of extra stabilisation. Handholding heavy lenses is highly dependent on technique so can vary greatly between people. I’m still learning but the size/weight of the 120-300mm doesn’t present me with too much of a problem. Some great advice on long lens technique here: http://www.leewebb.co.uk/section458554.html
On the whole this lens feels and looks like it should for the money paid for it.
A photo of me holding the lens to get a better idea of size:
This is the single biggest problem most people have with this lens. There are many reports of both autofocus and image stabilisation systems breaking and some people have reported having to send the lens for repair multiple times. Lensrentals.com report that 5 of 17 lenses have had to be sent for repair due to electrical failures: https://www.lensrentals.com/rent/canon/lenses/supertelephoto/sigma-120-300mm-f2.8-ex-dg-os-apo-hsm
I knew about these problems when I bought the lens as I had researched it carefully first however I decided it was worth the risk anyway!
When I first got the lens it would autofocus fine then after a couple of weeks the autofocus motor appeared to get stuck at infinity or halfway through the zoom range, at first this was solved by a quick turn of the manual focus ring however as the problem worsened this required more and more effort. I sent the lens away to Sigma UK and it came back within a week working perfectly. Hopefully this won’t happen again and leave me in the middle of the Kalahari Desert with a rather expensive doorstop!
If making your money depends on your lens working perfectly every day then invest more money in a more reliable lens however if you can take the risk or can handle having to send your lens away every now and again then you can save yourself a lot of money. For me the risk seemed to be worth it, I just hope the gamble pays off.
Image Stabilisation (OS)
The image stabilisation claims to allow you to shoot with 3-4 stops slower shutter speed and I would believe this. Obviously this depends on your ability to hold a large and heavy lens steady (see link in the build quality section) but I have found it invaluable and am certain that the majority of shots taken with this lens wouldn’t have been useable with the stabilisation turned off.
For example this photo taken at 1/50th of a second at 420mm with a monopod (and my monopod technique isn’t great):
The autofocus speed is good and it’s fine for what I need but I wouldn’t describe it as “blistering”, a term commonly used to describe the AF of the Canon 300mm f/2.8. I have never used the Canon 300mm so I cannot compare but the AF of the sigma is fast enough for me.
The AF accuracy again is good but I’m not blown away and it sometime hunts a little especially if there are twigs or grass in front of the subject although I think any lens would struggle with this.
The AF is very quiet however it does make a clicking noise when it changes direction which can be a little annoying but I rarely notice it out in the field.
Here are some photos I have taken with this lens. All fully edited and shot as I normally would and not for testing purposes: