Sigma has been on a roll the last few years, releasing some high performance lenses like the 85mm F1.4, 35mm F1.4 and recently the 18-35mm F1.8 crop sensor zoom lens. Those newer lenses are great, but Sigma has always had a segment of lenses that have been a great value for the money over the years. While third party lenses do have a certain stigma about them, some of that comes from the bad experiences of a few well known users, and the rest often comes down to brand elitism. While my experience with third party lenses is limited, I have not had to deal with lemon yet. The issue of lemons becomes an even greater risk when purchasing used lenses, but some fears simply have to be overcome in order to get the lenses you need, within your budget.
I had to go through that process when I picked up a used Sigma APO 120-300mm F2.8 EX DG HSM recently. The lens itself shows signs of use on the outer metal casing, but not signs of drops or abuse. More importantly the lens is optically pristine.
Build Quality and Handling:
The outer barrel of the lens is metal, painted with a slightly rough crinkle finish. The result of the metal construction is that the lens is extremely tough, and heavy (approximately 2900g). The zoom and manual focus rings are covered with a firm rubber that makes turning them a cinch. The zoom ring itself feels a little stiff, yet it turns smoothly. The stiffness is likely a result of the weight of the lens elements that are being moved while zooming. Both zooming and focusing of the lens elements are internal, so there is no moving parts.
Unlike many modern lenses there are no switches on the lens body. Yes, not even a switch to turn off auto focus. This might just be the case with the F mount version of the lens. The lens also lacks any kind of focus limiter switch, which is a little disappointing. I say that because the lens does focus as close as 1.5m, which is rather close for a F2.8 lens with the 300mm focal length. Most of the fixed 300mm F2.8 lenses out there do not focus closer than 4-5m.
One handling issue I have with the design of the lens is how close the focus ring is to the zoom ring. There were a number of times on my first outing when I would reach for the zoom ring, only to grab and turn the focus ring by mistake. I am guessing that with time I will get used to the placement of the different rings, but for now it is a little annoying.
When comparing the Sigma 120-300mm F2.8 to the likes of the Nikon AF-S 300mm F4D IF-ED, the size of the Sigma lens becomes obvious.
While both lens falls into the short end of super telephoto range, neither of are among the biggest SLR lenses by any means. For comparison, the fixed 300mm F4 Nikkor is about the same size as a standard 70-200mm F2.8 lens. In addition to the physical size difference, the Sigma zoom weighs 1500g more than the Nikkor. With that being said, I actually find the Sigma easier to carry over my shoulder than the Nikkor, because it balances better. One of the advantages of a F2.8 lens is that it allows more light in, which means that auto focus should be faster an more accurate. F2.8 telephoto lenses can also accept teleconverters without loosing as much light. Even with a 2x teleconverter the Sigma would still have a maximum aperture of F5.6.
One of the advantages of the Nikkor over the Sigma is the focus limiter switch, which prevents the lens from focusing on subjects closer than 3m. I did not find accidental close focusing a big issue on my first outing with the Sigma, but the possibility is there. The only real downside of the Nikkor is the narrower maximum aperture, which means that it is only truly usable with a 1.4x teleconverter.
Initial Field Report:
While I've only had the Sigma out a few times, it has performed extremely well. Optically I have not noticed any issues in the aperture ranges that I shoot wildlife with (F4-F8 in good light). Auto focus is snappy and extremely quiet. The speed does not match the likes of the AF-S 300mm F2.8G VRII, which I had the opportunity to try out last year, but it is very respectable. Due to the lack of a focus limiter hunting can be an issue, but thanks to the focusing speed you can easily reacquire most subjects.
So far I have only used the lens on it's own, because Nikon teleconverters do not seem to work well with Sigma lenses. There are two reasons for this, 1) without modification Nikon teleconverters physically will not mount on Sigma lenses. 2) There are known auto focus issues. While I have no direct experience of this, since I am not willing to modify my Nikon TC, well known reviewers have reported auto focus problems. I will be testing the lens with the Sigma APO 1.4x EX DG and APO 2.0 EX DG teleconverters once they arrive.
I will be posting a follow up, a full review, once I have had time to put the lens through a few months of use.