These 13 Pentax 645 lenses are rated for infrared photography from real-world tests by IR photographers. Ratings are Good (8 lenses), Maybe (5 lenses), 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.

Zooms

IR Focal
Length		 Minimum
Aperture		 Lens Filter Weight Notes Images
Good 33-55mm ƒ/4.5 smc PENTAX-FA 645 Zoom 33-55mm F4.5 AL
 ⌀82mm 585 g Slight hot spot at ƒ/22, perfectly usable at all focal lengths  
Maybe 45-85mm ƒ/4.5 smc PENTAX-FA 645 45-85mm F4.5
KEH B&H		 ⌀77mm 880 g Hot spot starts at ƒ/8; usable up to ƒ/22 at 85mm, ƒ/16 at 65-75mm, ƒ/11 at 45-55mm  
Good 55-110mm ƒ/5.6 smc PENTAX-FA 645 55-110mm F5.6
 ⌀82mm 500 g No hot spot  
Good 80-160mm ƒ/4.5 smc PENTAX-FA 645 80-160mm F4.5
 ⌀77mm 1,018 g No hot spot  

Primes

IR Focal
Length		 Minimum
Aperture		 Lens Filter Weight Notes Images
Maybe 35mm ƒ/3.5 smc PENTAX-FA 645 35mm F3.5 AL [IF]
Adorama 		⌀82mm 324 g Hot spot starts at ƒ/8, usable up to ƒ/22 or ƒ/32 in very bright areas  
Good 35mm ƒ/3.5 HD PENTAX-D FA 645 35mm F3.5 AL [IF]
 ⌀82mm 570 g Hot spot starts at ƒ/11, usable up to ƒ/22  
Maybe 45mm ƒ/2.8 smc PENTAX-FA 645 45mm F2.8
 ⌀67mm 476 g Hot spot starts at ƒ/5.6, usable up to ƒ/8  
Good 55mm ƒ/2.8 smc PENTAX-A 645 55mm F2.8
 ⌀58mm 320 g Slight hot spot at ƒ/22, perfectly usable  
Good 75mm ƒ/2.8 smc PENTAX-FA 645 75mm F2.8
KEH 		⌀58mm 215 g Almost no hot spot  
Maybe 120mm ƒ/4 smc PENTAX-FA 645 120mm F4 Macro
KEH Adorama 		⌀67mm 735 g Hot spot starts at ƒ/8, usable up to ƒ/22 in very bright areas  
Good 135mm ƒ/4 smc PENTAX 645 135mm F4 LS
 ⌀58mm 470 g No hot spot  
Maybe 150mm ƒ/2.8 smc PENTAX-FA 645 150mm F2.8 [IF]
KEH 		⌀67mm 500 g Hot spot starts at ƒ/8, usable up to ƒ/16 in very bright areas  
Good 200mm ƒ/4 smc PENTAX-FA 645 200mm F4 [IF]
KEH 		⌀58mm 669 g Hot spot starts at ƒ/11, usable up to ƒ/32  

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What the ratings mean. Hot spots usually appear as you increase the lens ƒ-number, so each rating depends on the lowest ƒ-stop where a hot spot shows and how severe it is, and the thresholds differ by sensor format.

  • Good: No hot spots, or one that starts at ƒ/11 or higher where diffraction impacts image sharpness.
  • Maybe: Contains a mild hot spot that starts at ƒ/5.6 or ƒ/8 and is correctable in editing.
  • Bad: A hot spot that starts at ƒ/4 or lower, or is hard to correct in editing.
  • Unknown: No data reported.

How reports are checked and rated

Pentax 645 Lens Mount Adapters

Use an adapter to mount these lenses to many mirrorless cameras.

B&H - Pentax 645 lens mount adapters