Sigma 150-500mm f/5-6.3 Auto Focus APO DG OS HSM Telephoto Zoom Lens for Canon Digital SLR Cameras

I've only had this lens for 24 hours, so any reliability issues aren't taken into consideration at this point. I am solely rating this on my first 3-hour hike with this lens, using my Nikon D5100.First of all, it's massive and weighs a lot. Be prepared to tire out your arms a little, taking this on a hike or walk, but it didn't bother me too much.First impressions:-Solid build, as always with Sigma. Heavy, but looks and feels very sturdy. The focus ring, zoom, and switches are all smooth and well-made-Incredible image quality. I took a couple hundred pictures of birds, chipmunks and prairie dogs and they all exceeded my expectations once I loaded them onto my computer. The images were so sharp from the lens (handheld on cloudy day) that I could reduce the noise from using a high ISO drastically and my images turned out beautifully. The optic stabilization seems to be top-notch. The color and contrast are SUPERB. I have not noticed any image quality issues.-I have not seen ANY problems at 500mm yet. The 500mm images I shot look nice and sharp. I did not close my aperture any more than f/11, so I do not know how it performs at narrow apertures. I typically shot around f/9 with 2000 ISO, between 400-500mm. Normally, 2000 ISO adds too much noise on my D5100 but with the lens it wasn't an issue.-Autofocus is incredibly quietSo far so good. If I decide this lens isn't as good as I thought, I'll change my rating. At the moment, it's a new favorite.UPDATE: 18 months of use. This is still a great lens. As a telephoto, you should probably shoot with a fast shutter. I find my images to be reliably high quality at 1/1,000 or faster, so this lens works best with a body that is good in low light. Focus can be somewhat unreliable in low light, so just be careful and check yourself when the light isn't great.When used properly (accurate focus, fast shutter) the images are tack sharp and beautiful.

Is the Sigma 150mm to 500mm zoom lens as good as a $3k Nikor lens? No. On the other hand, is the Nikor lens three times as good as the Sigma? Again, no. If money were no object, the Nikor lens would win out. However, if you're like me, money IS an object. Sure it would be nice if it were f2.8 rather than f4.5. It would also be nice to have more expendable money to spend on a lens. That said, this lens is a bargin in my book. My tests show it to be very sharp. As sharp as the Nikor... ??? It would probably take better eyes than mine to see much difference. The Sigma is big and heavy, but not as much as you might imagine for a 150mm to 500mm zoom lens. It feels very solid, focuses fast and accurately (auto focus), and has all the features of the more expensive Nikor lens... including image stabilization. Ahh... there's my one complaint. The mechanism (servo motor?) that operates the image stabilization function is noisy. You can actually hear it doing its job. Whereas, the VR Nikor lenses I have are totally silent.I bought this lens to take on safari in Botswana, and my testing to date convinces me it was a good and cost-effective investment. I also took advantage of the Amazon special priced Nikon D300-Sigma lens combo, which made it an irresistable deal. (upgraded from D200)

I am writing this review from the perspective of a former user of the Nikon 80-400VR (2 years) and Sigma 120-300 f/2.8 (3 years). The Sigma 120-300 is incredible piece of glass that is even sharper than Sigmas 300mm f/2.8 prime. The Sigma 120-300 works very well with a matching Sigma 1.4x TC which is how I used it 80% of the time. Even with a TC is matches or slightly exceeds the 150-500 in the overlapping range but is obviously much faster glass and thus freezes motion and blurs backgrounds better. But the range is more limited, the lens is heavier, costs 3x more and doesn't go to 500mm which is what I wanted. The hood and tripod collar construction is inferior to the faster pro lens. For example, the hood can easily be crushed in your hand like a plastic cup, and the tripod collar cannot be removed without removing the lens but both are functional and quality is very acceptable at this price point.The Sigma compares favorably to the Nikon 80-400 in that is focuses faster since it has a built in HSM motor. 150-500mm is more desirable range than 80-400, at least for my needs, and I shoot DX format. I also own a Nikon 70-200 f/2.8 which pairs much better with a 150-500 than either of these two lens mentioned above - the Nikon 70-200 performs very well with a Nikon 1.4x TC so I have a 105 - 280mm f/4 as well. With proper technique the Sigma matches and possibly exceeds the sharpness of the Nikon 80-400 but again, it has a better/different range.The lens seems sharpest at 150-400mm and a tad soft near the 500mm end so you definitely need to stop down with f/9.5 being a good compromise if you have the light, else f/8. OS works very well and unlike other reports mine (purchased in June 2010) does not make very loud clicking sounds when OS is engaging. It is important to wait until OS is engaged which may take about a second else your shots will not be sharp. The best way to tell is to look through the viewfinder with the shutter pressed halfway and wait until gyro is spinning and the 'obvious shake subsides'. Then squeeze, don't press the shutter by rolling your finger down.Tip, the zoom ring is stiff and can be aggravating to turn. However, instead of using the zoom ring to zoom, instead grab the end and use it like a push-pull zoom. This method works very well and very smoothly. Also, with long lenses you must avoid shutter speeds of 1/8 - 1/60 sec unless you are using some type of mirror lock up since mirror slap vibration with FL's over 100mm are a known cause of slight blurring.This is not a pro lens but a very good lens with a very good range that will take very good pictures if, and only if, you exercise good long lens technique. With manual focus a Sigma 1.4x TC can work if stopped down and when you are not after large prints but smaller, or especially web-sized images. With such a narrow field of view the slightest movement can cause blur - the nature of all long lenses. This lens is a great value, I just wish they could have made it an f/5.6 instead of f/6.3 and I think most people would not mind paying about 20% more for that half stop. Also, the lens has a zoom lock to prevent lens creep which is great. I only wish sigma also included a limit switch like the Nikon 80-400 has and which is very useful for faster focusing.Note: At the time of this review Sigma has issued a notice that there may be a problem with some lenses with regard to Auto Focus (keeps hunting) with serial numbers between 10674301 and 10972000. Mine is in this range but does not have the problem. If yours does have the problem it may be best to return/exchange the lens since Sigma service will return the lens to Japan to be fixed instead of repairing in the US and this can take 4-6 weeks - see report here [..]