I have experience with only a very small percentage of Pentax's current lenses, so I cannot even begin to offer my views on particular lenses. However, what I can do, is sort. I took all the lenses on Pentax's hardware roadmap and put them into a spreadsheet and sorted them, to try to understand what's going on. I did this for me, but I'm sharing it with you. Note: for simplification, I've ignored the alphabet soup Pentax puts into the names of all these lenses. I've tried to pull out the important bits into the third column, but for the full explanation, this website has an excellent guide. Note #2: Pentax has a "Limited" series of lenses which has nothing to do with their production run and everything to do with their physical size: Limited lenses are very compact, but also come at unusual focal lengths and maximum apertures. So, with no further fanfare, here's the chart.
K-mount Standard Zooms
These lenses are the jack-of-all-trade variety that are the highest sellers for all camera. Pentax seems to offer several upgrade paths for those looking to improve upon the kit lens, with some have a slightly wider focal length range, some featuring constant apertures throughout the zoom range, and some giving full-frame coverage.
|16-50mm||f/2.8||Pro-level crop frame choice|
|16-85mm||f/3.5-5.6||More zoomy than the kit lens|
|17-70mm||f/4||Slightly better than the kit lens|
|20-40mm||f/2.8-4||Limited series (physically small)|
|24-70mm||f/2.8||Full-Frame Pro option|
|24-105mm||f/3.5-5.6||Full-Frame budget option|
K-mount Super Zooms
For people who want an interchangeable lens camera but don't want to interchange the lens, there exist super-zoom lenses: lenses which combine the focal lengths of a standard zoom with those of a telephoto zoom.
|18-135mm||f/3.5-5.6||Like the kit lens but zooms in more!|
|18-270mm||f/3.5-6.3||Like the first one but even more zoomy!|
K-mount Telephoto Zooms
For those new to photography, usually the first lens they buy after the one that comes with the camera is a telephoto zoom – it is common to find an entry-level lens or two in this category. But because this range is so heavily used by working professionals for everything from portraits to photojournalism to wildlife to sports, there tends to be an ever-increasing list of selections available, with the sky the limit on quality, weight, and price.
|50-135mm||f/2.8||High-end crop-frame option|
|50-200mm||f/4-5.6||Slightly smaller entry level option|
|55-300mm||f/4.5-6.3||Retractable entry level option|
|60-250mm||f/4||Bird lens on a budget?|
|70-200mm||f/2.8||Full Frame pro choice|
|150-450mm||f/4.5-5.6||Full Frame wildlife choice|
K-mount Wide Angle Zooms
"Hey," you say to yourself, "I have a standard zoom and a telephoto zoom, why not a wide angle zoom?" Some people do indeed think this way, and so Pentax makes these lenses to sell to them.
K-mount Prime Lenses
Ok, finally, the good stuff. Prime lenses are the best, but probably also the most confusing part of Pentax's lineup. They're also the part I'm most interested in.
|15mm||f/4||Limited series pancake|
|21mm||f/3.2||Limited series pancake|
|31mm||f/1.8||Full frame limited series|
|35mm||f/2.8||Macro Limited series|
|40mm||f/2.8||Limited series pancake|
|43mm||f/1.9||Full frame limited series|
|50mm||f/2.8||Macro full frame|
|50mm||f/1.4||Full frame older version|
|50mm||f/1.8||Relatively compact lens|
|70mm||f/2.4||Limited series pancake|
|77mm||f/1.8||Full frame limited series|
|100mm||f/2.8||Macro full frame|
|200mm||f/2.8||Mostly full frame|
|300mm||f/4||Mostly full frame|
|560mm||f/5.6||Basically a telescope|
Writing this blog post has helped me understand Pentax's lineup – something I wanted to do before spending any money on it. Hopefully, if you're reading this, this post is helpful to you, too.