Most photographers in the market for an SLR go with a Canon or a Nikon camera. But, despite their market share, the big two aren't the only game in town. Besides, both companies are winding down their optical viewfinder SLR cameras in favor of mirrorless models with electronic viewfinders. The Pentax brand has been around for a long time and, if you learned photography in the 70s or 80s, you probably picked up the classic manual focus K1000 SLR at some point. And, importantly for optical viewfinder purists, Pentax is sticking with SLRs, while the rest of the photo world moves to mirrorless systems.

In the digital world, Pentax SLRs set themselves apart from the competition by concentrating on build quality rather than bells and whistles. Even the budget-friendly K-70 ($649.95) has a glass pentaprism viewfinder, a stabilized image sensor, and extensive weather sealing—features that are typically only available in bodies that cost over $1,000 for other systems.

On the high end, the K-3 Mark III ($1,999.95) includes the best autofocus and video capabilities of any Pentax camera yet. It can focus and track subjects quickly, plus records in 4K. It costs as much as some cameras with full-frame sensors at around $2,000, but long-time Pentaxians finally have access to a camera that goes toe-to-toe with bigger brands for capturing subjects in motion.

Like most entry-level models from Nikon and Canon, most Pentax SLRs use the APS-C sensor size. There is one full-frame model available, the 36MP K-1 Mark II ($1,999.95). You can use APS-C lenses with it—we've tested some and found that a few cover the whole sensor and are decent performers—but, for the best results, look for lenses marked as FA or D FA if you shoot with the K-1.

Pentax doesn't offer nearly as many lenses for its system as other manufacturers do for theirs and third parties don't support it quite as extensively, either. Sigma released a handful of its Art and Contemporary K-mount lenses, but many have gone out of production; you can still get the 30mm F1.4 Art for APS-C and 35mm F1.4 Art for full-frame, but that's it. Tamron doesn't offer any of its current lenses for the system but does license out some of its designs under the Pentax banner.

That said, all the basics are available. You might just have one or two options for a particular type in the mount, and some options might seem a bit outdated compared with lenses from other systems. For instance, whereas Pentax still relies on screw-driven focus for many lenses, most other systems go for quieter in-lens focus motors. That said, you won't find a match for some Pentax-exclusive lenses on competing mounts. The svelte DA Limited series, a line of compact lenses with metal construction, has obtained an almost cult-like following, for example.