Top positive review
102 people found this helpful
great lens but you must learn how to use it.
on January 11, 2012
I want to support Sigmas efforts to develop a lens that covers these extreme ranges in a usable zoom so I am writing this review to put the professional photographers mind at ease when considering this lens. This lens is an important lens for me and can be for many other professional photographers as well.
I have been shooting professionally for about 25 years and have worked with everything from 35mm film to 8X10 film. I shoot advertising, food, catalogs and architecture and went digital in 1999 with the Kodak system mounted to Nikon bodies. I switched from Nikon to Canon for the full frame Canon 5D and currently shoot Canon 5D MKIIs and have all the usual L lenses.
Digital sensors are different than film in that film is actually three demential. The "grain" in film is three-dimensional crystals and can easily react to light even if that light arrives from extreme angles. Digital sensors are flat planes with pixel wells and react differently to light. The lens manufacturers figured this out and acted accordingly and today we have lenses that are much better than yesterdays film lenses. These lens improvements are not as critical in moderate telephotos around 100mm but becomes more significant at focal lengths shorter than 28mm. With all this in mind I figured that Sigma has addressed these issues and probably developed a pretty nice lens. After reading as many reviews as possible and weeding out the less experienced users I found that many people were satisfied given the limitations and the cost of this lens. First of all this is a zoom and the compromises must be considered when forming your expectations. Second, this lens is pretty cheap in cost so that is also factored in with my opinion. Third, I had realistic expectations and didn't expect this lens to be exceptional at any focal length. That being said I am pretty happy with this lens. There have been some reviews that noted this lens tends to have zones of sharpness and zones of softness. I too have noticed this behavior but upon closer examination I began to realize that the problem lies with hyper focus rather than softness. With traditional wide lenses one chooses a distance "range" that is deemed sufficient to carry focus and then sets the lens accordingly. This usually gives good results and it's easier to achieve the with wide angle lenses. To test a lens like this you shoot a flat surface such a the side of a building and look at the results at 100%. Normally you expect to see some softness in the corners. This lens seems to be different in that it has pretty a shallow DOF given it's extreme wide angle. So when you shoot a flat building the results with this lens are pretty bad and it's easy to pass this lens off as not good. This lens has aspheric elements to compensate for the usual problems associated with wide angle lenses and it seems that this lens also has aspheric DOF. I have done considerable testing in real world situations and have found that in situations such as shooting buildings with deciduous trees in front of them where you can see the building through the trees an interesting phenomenon occurs. Parts of the trees are in focus and parts of the building are in focus as if there are waves of DOF in the image. It is like some areas are in focus and right behind those areas there is a zone of softness and then and behind that area it is sharp again! Stop the lens down and the sharp areas become sharper and the out of focus areas become sharper but there seems to be little increase in overall DOF! I have learned that where the lens is focused on the scene is VERY critical and if it's off by even a small amount the lens will seem out of focus which is contrary to extreme wide lenses because one would expect a wide lens combined with a smaller aperture would improve DOF to the extent that where the lens if focused does not matter. NOT so with this lens. So when you read that this lens is not sharp the reviewer may not be focusing the lens properly. The trick with this lens is to use it manually and set it to infinity or very close to infinity when shooting scenics and carefully focus the lens when shooting anything closer than 20 feet. One would think that 20 feet on a 12mm lens would be carried by hyper-focus but with this lens it is not!
It is a very good lens and I am very happy with it. I respect it's limitations but I am confident enough to use it on any jobs I have.
I have now had plenty of time to shoot several jobs with this lens and I am very impressed with it. As I said above this lens requires some work to get the best results but once I figured out how to focus this lens and process the images I could not be happier with the results! I can't keep it on one body all the time because the longer 25mm focal length is too short for many uses and I find my self needing a longer lens like the 16-35mm but when I need a lens wider than 25mm I have no hesitation with using this lens in place of the Canon L lenses. This lens paired with the 24-105 L is really a nice combination because I can get a wide view and also a nice telephoto look with the 24-105 and when I need to go really wide I have this lens. And I don't have to worry about explaining to clients the differences in images when I mix the images from the Sigma with the Canon lenses because there is little difference.