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“Pentax K-x” is ambiguous: there’s the 1975 Pentax KX film SLR and the 2009 Pentax K-x, a 12.4MP APS-C digital DSLR that took its name as a tribute to that earlier camera. This guide is written for the far more common 2020s search — the digital K-x — which uses Pentax’s K-mount and autofocuses via its own in-body screw-drive motor, so it works with both current DA-series autofocus lenses and manual-focus K-mount glass. Every pick below is a lens Pentax or a third party still sells new today, not a discontinued relic.
| # | Product | Price | Where to buy |
|---|---|---|---|
| 1 | HD Pentax-DA 18-55mm F3.5-5.6 AL WR | $150-$180 | Amazon · eBay |
| 2 | HD Pentax-DA 55-300mm F4-5.8 ED WR | $250-$330 | Amazon · eBay |
| 3 | smc Pentax-DA 35mm F2.4 AL | $130-$160 | Amazon · eBay |
| 4 | smc Pentax-DA 50mm F1.8 | $130-$160 | Amazon · eBay |
| 5 | HD Pentax-DA 40mm F2.8 Limited | $350-$450 | Amazon · eBay |
| 6 | HD Pentax-DA 70mm F2.4 Limited | $450-$600 | Amazon · eBay |
| 7 | HD Pentax-DA Fish-Eye 10-17mm F3.5-4.5 ED | $650-$750 | Amazon · eBay |
| 8 | HD Pentax-DA* 16-50mm F2.8 ED PLM AW | $1,350-$1,450 | Amazon · eBay |
| 9 | Rokinon/Samyang 85mm F1.4 AS IF UMC (Pentax K-mount, manual focus) | $300-$350 | Amazon · eBay |
| 10 | Samyang 35mm F1.4 AS UMC (Pentax K-mount, manual focus) | $300-$350 | Amazon |
The picks, in detail
HD Pentax-DA 18-55mm F3.5-5.6 AL WR
Pentax’s current standard kit zoom for APS-C K-mount bodies, weather-resistant and the natural all-purpose lens for a K-x.
- APS-C DA lens (27-84mm equivalent)
- Weather-resistant (WR) construction
- Autofocus via the K-x’s in-body screw-drive motor
- Cheapest way to cover a useful everyday zoom range
- Currently in production, easy to find new
- Variable f/3.5-5.6 aperture, dim indoors
HD Pentax-DA 55-300mm F4-5.8 ED WR
Pentax’s current telephoto zoom for APS-C bodies, launched at $449.95 and now commonly found new for less.
- APS-C DA lens (84-460mm equivalent)
- Weather-resistant construction
- ED glass elements
- Long reach for wildlife/sports on a budget
- Slow variable aperture at the long end
smc Pentax-DA 35mm F2.4 AL
A cheap, fast normal prime (about 53mm equivalent on the K-x’s APS-C sensor) that’s stayed in Pentax’s current lineup for years.
- APS-C DA prime
- f/2.4 max aperture
- Compact and light
- One of the least expensive fast primes in any camera system
- Plastic mount and build, feels basic
smc Pentax-DA 50mm F1.8
A classic fast portrait-length prime (about 75mm equivalent), currently sold new and one of the sharpest budget lenses in the K-mount lineup.
- APS-C DA prime
- f/1.8 max aperture
- Fast, quiet autofocus
- Excellent background blur for the price
- Very sharp wide open
- No weather sealing
HD Pentax-DA 40mm F2.8 Limited
A pancake-style prime from Pentax’s premium metal-bodied Limited line, still in current production.
- APS-C DA Limited prime
- f/2.8 max aperture
- All-metal Limited-series build
- Extremely compact, barely adds bulk to the K-x
- Premium build quality vs. the standard DA line
- Pricier than the standard 35mm/50mm primes above
HD Pentax-DA 70mm F2.4 Limited
A longer Limited-series prime (about 107mm equivalent) built for portraits, sold new in both black and silver.
- APS-C DA Limited prime
- f/2.4 max aperture
- Metal Limited-series build
- Excellent portrait compression on APS-C
- Premium Limited-line construction
- Narrower field of view limits it to portrait/detail work
HD Pentax-DA Fish-Eye 10-17mm F3.5-4.5 ED
Pentax’s current fisheye zoom, still sold new by Ricoh/Pentax and through Amazon for full-diagonal 180-degree shots at 10mm.
- APS-C DA fisheye zoom
- 180-degree diagonal field of view at 10mm
- ED glass elements
- Only current-production fisheye option in K-mount
- Niche, special-purpose lens — not an everyday zoom
HD Pentax-DA* 16-50mm F2.8 ED PLM AW
Pentax’s current professional standard zoom for APS-C bodies, launched at $1,399.95 with a fast PLM autofocus motor and weather sealing.
- APS-C DA* professional zoom
- Constant f/2.8
- PLM autofocus motor, all-weather sealing
- The sharpest, most capable standard zoom Pentax currently sells for APS-C
- By far the most expensive lens on this list, arguably overkill for a 2009 body
Rokinon/Samyang 85mm F1.4 AS IF UMC (Pentax K-mount, manual focus)
A budget manual-focus portrait prime still sold new in Pentax K-mount, designed for full-frame but usable on the K-x’s APS-C sensor for a tighter portrait length.
- Manual focus, manual aperture
- f/1.4 max aperture
- Full-frame image circle (works on APS-C too)
- Very fast aperture for the price
- No autofocus motor needed since it’s fully manual
- Manual focus only — no autofocus confirmation dot issues on some bodies
Samyang 35mm F1.4 AS UMC (Pentax K-mount, manual focus)
A fast, currently-sold manual-focus wide prime in Pentax K-mount, a budget way to get f/1.4 low-light performance.
- Manual focus, manual aperture
- f/1.4 max aperture
- K-mount (KAF) fitting
- Fast aperture for low-light or shallow depth of field
- Fully manual — slower to shoot moving subjects than the autofocus DA lenses
Buying tips
- This guide treats “Pentax K-x” as the 2009 digital DSLR, not the 1975 Pentax KX film SLR — both share the K-mount, but the digital K-x is what almost every 2020s search actually means.
- The K-x has its own in-body autofocus motor, so it autofocuses with standard screw-drive K-mount lenses, not just SDM/PLM lenses — you aren’t limited to lenses with a built-in motor.
- DA-series lenses are designed for the K-x’s APS-C sensor and give the field-of-view figures above; full-frame FA/Limited lenses will also mount and meter but crop tighter than their marked focal length suggests.
As an Amazon Associate and eBay Partner, toptenpick.com earns from qualifying purchases. Prices and availability are subject to change.