Have you ever wanted more of your picture in your photographs? One of the easiest ways to get more into your pictures is to purchase and use an ultra-wide angle lens. A wide-angle lens, by definition, has a focal length shorter than the short side of the camera sensor. The APS-C sensor, used in all Pentax DSLR’s, is approximately 24 mm x 16 mm. This means that any lens with a focal length between 24mm and 16mm can be considered wide angle. An ultra-wide angle lens has a focal length less than 16mm.
When most people think of ultra-wide angle lens photographs, they imagine pictures with extreme distortion. We have all seen photographs that stretch from horizon to horizon and indeed they are distorted. All ultra-wide angle lenses provide the photographer a wider view with some distortion, which is the appeal of the ultra-wide angle lens.
Ultra-wide angle lenses come in two types: Fisheye lenses with curvilinear barrel distortion and rectilinear lenses. Fisheye lenses are very useful in some situations and can create unique photographs because of their distortion. Rectilinear lenses are designed so straight lines in a photograph will appear relatively straight and thus lack the extreme distortion that is characteristic of fisheye lenses. Fisheye lenses have their place because of the distortion but rectilinear lenses are another story. Rectilinear lenses are more versatile and they have use both in architectural and landscape photography.
Currently Pentax makes two ultra-wide angle zoom lenses, one is a fisheye and the other is a rectilinear lens. In this review, we'll examine the three popular ultra-wide angle reticular zooms for the Pentax system, including the Pentax DA 12-24mm f/4, the Sigma DG 12-24 f/4.5-5.6, and the Tamron SP AF 10-24mm f/3.5-4.5 DI II.