The Pentax K mount covers every generation of Pentax bayonet, the original K, plus KA, KAF, KAF2, KAF3 and KAF4, which share the same physical bayonet and flange distance. Older manual K-mount lenses mount on current Pentax DSLRs, though autofocus and electronic aperture control vary by generation.
These 8 Pentax K lenses are rated for infrared photography from real-world tests by IR photographers. Ratings are Good (7 lenses), Maybe (1 lens), Bad (0 lenses), and Unknown (0 lenses) for hot spots, the bright spot some lenses leave in the center of an infrared image, and follow the thresholds below.
| IR | Focal Length |
Minimum Aperture |
Lens | Filter | Weight | Notes | Images |
|---|---|---|---|---|---|---|---|
| Good | 19-35mm | ƒ/3.5-4.5 | Cosina / Vivitar / Phoenix / Promaster 19-35mm ƒ/3.5-4.5 |
⌀77mm | 320 g | Submitted by Rich Lukey | View images |
| Good | 31mm | ƒ/1.8 | smc PENTAX-FA 31mm F1.8 AL Limited KEH |
⌀58mm | 350 g | No hotspot. | |
| Good | 35mm | ƒ/2.8 | smc PENTAX-DA 35mm F2.8 Limited Macro KEH |
⌀49mm | 215 g | My best lens on my converted Pentax K-7; good sharpness wide open; very sharp at ƒ/5.6 and above. Charles Kinghorn | |
| Good | 43mm | ƒ/1.9 | smc PENTAX-FA 43mm F1.9 Limited KEH Adorama |
⌀49mm | 155 g | No hotspot. | |
| Good | 50mm | ƒ/1.7 | smc PENTAX-M 50mm F1.7 KEH Adorama |
⌀49mm | 185 g | No hotspot. | |
| Good | 77mm | ƒ/1.8 | smc PENTAX-FA 77mm F1.8 Limited |
⌀49mm | 270 g | Hotspot starts at ƒ/11, but it’s usable up to ƒ/22. | |
| Maybe | 85mm | ƒ/1.4 | smc PENTAX-FA* 85mm F1.4 IF |
⌀67mm | 620 g | Hotspot starts at ƒ/8, but it’s usable up to ƒ/22. | |
| Good | 135mm | ƒ/1.8 | smc PENTAX-A* 135mm F1.8 |
⌀77mm | 865 g | No hotspot. |
Pentax K Lens Mount Adapters
Use an adapter to mount these lenses to many mirrorless cameras.