My least favourite lens not only happens to be the most expensive lens I own, but also the only lens that I bought new.
Under right conditions, the lens produces results that I can be satisfied. But more often than not, I find the lens to be a little difficult to use for a number of reasons.
The number one issue I have with the lens its maximum aperture. Since this is one of the most affordable Ultra Wide Angle lenses, the lens is quite slow compared to the other lenses that I own. With the limited ISO capability on my camera, using this lens indoors or under dark conditions is very challenging. I often end up with more noise or motion blurs in my photos.
The next challenge I have with this lens is distortion. Sure, some distortion is inevitable in designing this kind of a lens, but especially when I am shooting architecture or landscape, the level of distortion becomes unbearable as real world images gets twisted and disproportionate. At longer focal lengths, the distortion disappears, but the advantage of an Ultra Wide Angle lens disappears with it as well, as the focal length can easily be covered by my kit lens.
The next is lens flare. I have used this lens in many brightly-lit conditions, and this would have to be the lens that is most susceptible to lens flare.
Because the field of view is so wide, it sometimes encourages me to get closer to my subjects than I would normally. At the same time, it is difficult to fill the frame without making the picture look busy.
Another technical challenge I find is the lens' hunt for focus. Because there is so much going on in the frame, the camera can't decide what to focus on. I often find the lens to hunt for focus and eventually end up focusing on a wrong object. Because this is a lens designed for digital photography, manual focus is more difficult than my older counterparts.
The last technical challenge that I face is attaining proper exposure. Depending on the metering system I use, the image can be under- or over-exposed. I find that getting a proper exposure is an art in itself, as the camera has difficulty balancing the lights and darks of the image.
As for the pros for the lens, I like the image quality that this glass can provide. Despite all the difficulty that I find in using this lens, once those are overcome, I am usually pleased with the end result. The image is punchy and full of contrast, and I do enjoy the wide perspective when framed right.
Most lenses I own are old manual lenses anyway, which requires me to carefully compose, focus, and expose. One could perhaps say that the technical challenges of this lens are rather perceived due to my inexperience in photography.
There was a time a few years ago, when I put up the lens for sale on Kijiji. I am glad that I did not give up on it, as I think this is a lens that really shows my limitations as an aspiring photographer.
Soon, gone will be my days as a pixel-peeper where I would go through my photos at 100% Zoom level to see how "sharp" or "soft" my image is. I will embrace the flaws of this lens as character, and use it to my benefit in improving my photography skills.