Introduction. This page shows an optical comparison between the Sigma 15-30 Tokina 19-35 ultra-wide zoom lenses. These lenses are popular choices with owners of the latest generation of digital SLR users, because these cameras' small image sensors effectively "crop" the field of view. For example, a 19mm lens on a Canon D60 provides the same field of view as a 30mm lens on a conventional 35mm camera. A 15mm lens provides the same field of view as a 24mm lens on a conventional 35mm camera. This image shows the field of view difference between the 19mm Tokina and the 15mm Sigma using a Canon D60.
Given how much wide angle zoom lenses cost, these two lenses are two popular "budget" choices. The Tokina is a real bargain at just under $200, while the Sigma costs about $550. The Tokina is considerably smaller, and accepts standard 77mm filters. The Sigma is much larger (although not as heavy as its size might suggest) and accepts 82mm filters (using a supplied adapter that slips over the permanently affixed lens hood). The extra length of the Sigma is what makes the images below appear to be slightly different sizes even though they were taken from exactly the same place...the end of the Sigma lens was about 2-3 inches closer to the newspaper than the end of the Tokina lens.
Methodology. All images were taken using a Canon D60 digital camera, mounted on a tripod, using mirror lockup and self timer to eliminate any camera shake. The target was a newspaper page, taped to a wall, illuminated by daylight. The chart below shows cropped portions (from the center and edges) of several test images taken with the two lenses at various focal lengths common to each lens, and three different apertures.
Results. I encourage you to look at the images
below for yourself, but here is how I interpret these images.
Conclusions. It is difficult to make a choice between these two. If you need the wide angle that the Sigma provides, there is no choice...get the Sigma. It may not sound like much, but 15mm is quite a lot wider than 19mm. However, if you can live without the wide angle coverage of the Sigma, then I'd stick with the Tokina with no regrets. At about a third the price of the Sigma, the Tokina clearly gives the most bang for the buck.