The majority of my lenses are old, manual focus primes and I enjoy the solid feel and handling of a well-crafted, compact metal lens that you don't find anymore among today's efficient but homogenized products. Both K-x and K-01, like all Pentax DSLRs and unlike those from Canon and Nikon, benefit from having shake reduction built into the body, which further helps giving good old legacy glass a new lease on life. Unfortunately, the standard viewfinders in modern DSLRs are severely lacking. To help with manual focusing, I have fitted the K-x with a split screen viewfinder, but for manual focus lenses, the K-01 with its superb LCD and its focus peaking feature is still the better tool.

Here are the lenses I'm using with the K-x and the K-01.

The Sigma 10-20mm f/4-5.6 EX DC was a gift from the best of wives. Lenses this wide on APS-C were not made for 35mm SLRs, so there was no legacy lens alternative to this one.
Big Milk Big Milk

The SMC Pentax-DA L 55-300mm F4-5.8 ED is one of the two kit lenses that came with the K-x. It's an amazing value that I have yet to find a fault with. It is my most-used lens.
Supermodel Supermodel

The other kit lens is the SMC Pentax-DA L 18-55mm f/3.5-5.6 AL. I was not quite as thrilled with its output, and thought I might eventually replace it with a Tamron SP AF 17-50mm F/2.8 XR LD or a Sigma 18-50mm f/2.8 EX DC Macro, until shots like this made me reconsider:
Cacti Cacti

The SMC Pentax-DA 35mm f/2.4 AL, aka "Plastic Fantastic", fills the gap in my small auto-focus line-up for a fast normal lens and it does so admirably.
Twilight Twilight

The SMC Pentax-DA 40mm F2.8 XS is rather close in specs and performance to the DA 35, but it does something the DA 35 cannot do - it is tiny, and makes the K-01 fit in a coat pocket. This lens definitely deserves to be called a 'pancake'. Unfortunately, it appears that my copy does not open up all the way to f/2.8. I'm sure this could be fixed easily, but I haven't gotten around to opening it.
31.3.13 31.3.13

SMC Pentax-F 35-70mm f/3.5-4.5 - this is a recent acquisition among my auto-focus lenses. I can't really say I absolutely needed this one, but at 50 bucks, it didn't cost an arm and a leg either. The focus range nicely straddles the short end of the 55-300 and the long end of the 18-55. It's cheaply-built, but light-weight. It is also very sharp and I like the colors it produces. Compared to the 18-55 and the 55-300, the auto-focus is blazingly fast, but struggles as much in dimly lit rooms. While it is a perfectly fine lens, it is currently the most likely for me to get rid of if I need space in the drawer.
Faster! Faster!

Raynox DCR-150 macro converter lens - the 50mm f2.8 Macro or Vivitar Series 1 70-210mm usually get me close enough and are more convenient for casual use, but for true 1:1 magnification the Raynox can help do the job, here in combination with the Pentax DA L 1:4-5.8 55-300mm ED.
Mountaineer Mountaineer

The remainder of my lenses are all manual focus, most of them in M42 screw mount.

The SMC Pentax-M 50mm f2 goes for about 20$ on the used market, but it's a perfectly fine lens and my second-fastest in K-mount. Also, since it came with the first film SLR I bought in 1979, it has sentimental value for me, so it's a keeper.
Suspended Suspended

A Vivitar Series 1 70-210mm 1:2.8-4.0 (version 3 by Komine) that I managed to get for well under 100$. It lives up to its reputation of being able to compete with the better of modern designs at all levels except resistance to flare and chromatic aberration wide open. It easily surpasses them in terms of build quality. The macro function is a nice bonus with a magnification of 1:2.5. Weighing 860g, it's a chunky piece of equipment, so one's getting a good workout, too.
Hands and Feet Hands and Feet

Jupiter-9 85mm f/2, a Soviet copy of the pre-war Zeiss Sonnar 85mm design with fifteen aperture blades. My copy renders with a strong soft glow wide open, but sharpens up dramatically from around f/4. While not an all-rounder, this is a lens with character. This is wide open:
Camellia Camellia

Since my Jupiter-9 is a bit funky wide open, I was looking for a more robust, affordable alternative and found it in the Rokinon 85mm f1.4. It is manual-focus, but provides the A-setting for aperture control from the camera body.
Day 19 Day 19

Jupiter-37A 135mm f3.5, another Soviet M42 preset lens. It is sharp even wide open and its twelve aperture blades conspire for smooth out-of-focus highlights. One of my favorites.
Reinforcement Reinforcement

The SMC Pentax-A 50mm f2.8 Macro was made between 1984 and 1988. It is one of the sharpest lenses I own. Only 1:2 magnification, though, so not much better than the Vivitar 70-210, which is why it tends to stay at home when the Vivitar is in the bag.
Promise Promise

The Vivitar 28-70mm 1:3.5-4.8 MC Macro Focusing Zoom that I pulled out of a long-forgotten moving box the other day does not have the reputation of the coveted early Series 1 lenses, but apart from its bad zoom creep, I find it very decent. It was made by Cosina, sold for over 300$ in the 80s (also under the brands Minolta, Miranda, Praktikar and others), but these days, it can be had for a song. It has a PK-A mount, but mine did not work in aperture priority mode anymore, so I opened it and some superglue did the trick for fixing the stop-down actuator. The lens has eight aperture blades, is sharp, produces a nice bokeh and renders beautiful colors, so I'm glad I managed to fix it.
Incoming Incoming

Helios 44-2 58mm f2 made in 1978, an inexpensive Soviet copy of the Zeiss Biotar with eight aperture blades. Works well for portraits.
Sunnyvale Sunnyvale

Last, but certainly not least, seven Asahi Pentax Takumar M42 screw mount prime lenses from the 60s and early 70s. I can't believe the excellent shape these lenses are still in after all this time and what a bargain they are.

SMC Takumar 1:3.5/28:
#28 #28

Super-Takumar 1:3.5/35. Compact, solid, sharp - just a lovely little lens and a true bargain.
Focused Focused

Super-Takumar 1:1.4/50. This is the one with the slightly radioactive glass that yellows over time. It can be cured by exposing it to UV radiation for a while, but I didn't get around to fixing it yet. Shot wide open:
Pigtails Pigtails

Super-Takumar 1:1.8/55, wide open:
Gymnastics Gymnastics

Auto-Takumar 1:2.8/105:
Growing Up Growing Up

Super-Takumar 1:3.5/135:
The Red, White and Blue The Red, White and Blue

Super-Takumar 1:4/200:
Evening Stroll Evening Stroll