Pentax smc DA 15mm f/4 ED AL Limited review
The 15mm F4 is a member of Pentax's family of 'Limited' primes, which are unique amongst mainstream autofocus lenses in having a barrel sculpted entirely from high grade aluminium. Build quality is, in a word, superb, with fine engineering in every detail, complemented by markings which are engraved into the barrel as opposed to simply painted on. With its jewel-like construction, this is a lens which will certainly appeal to traditionalist photographers brought up on good old-fashioned manual focus SLRs and their all-metal primes.
The most unusual feature of the design is the built-in petal type hood, which retracts by sliding back into the lens body. While sliding hoods aren't anything new, they are generally seen on larger lenses (normally telephotos) and tend to be simple cylinders in shape; managing to squeeze one into a body this small is an impressive feat of design and engineering.
Compared to Tokina AT-X Pro 12-24mm F4 DX
One of the big attractions of primes is that they tend to be substantially smaller and lighter than zooms covering the same focal length. This is especially true at the wideangle end of the spectrum, with even slow zooms being distinctly heavy and bulky.
To illustrate this advantage, here's the 15mm F4 all packed up and ready to travel, alongside a fairly typical APS-C wideangle zoom, the Tokina AT-X Pro SD 12-24mm F4 (IF) DX (which is closely related to Pentax's own 12-24mm F4 design). While it's not quite as tiny as its 'Pancake' siblings (the 21mm F3.2, 40mm F2.8 and 70mm F2.4), the 15mm F4 is substantially less than half the size and weight of the zoom. This means that it takes up very little space in a camera bag, and will even fit into a coat pocket in a way a wideangle zoom most certainly won't.
On the camera
The 15mm F4 is decidedly petite, and sits comfortably on any size body from the large-ish K20D (left) to the tiny K2000 (right). It's a joy to use; the focus ring falls perfectly to hand, and the 'quick shift' system means focus can be adjusted manually even when the camera is set to autofocus mode. The sliding hood is well-designed and operates smoothly too.
Autofocus is driven by a screw-drive mechanism from the camera, and is therefore dependant primarily upon the capabilities of the specific body used. On the K20D we employed for testing, autofocus was generally fast, accurate and reliable, with no systematic problems. As always, it must also be noted that focus speed and accuracy is dependent upon a number of variables, including subject contrast and light levels.
Lens body elements
Reported aperture vs focal length
This lens allows an aperture range from F4 to F22 to be selected.
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