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Pentax 21390 HD DA 40mm f/2.8 Limited Lens — main product image
Pentax 21390 HD DA 40mm f/2.8 Limited Lens
Pentax 21390 HD DA 40mm f/2.8 Limited Lens
Pentax 21390 HD DA 40mm f/2.8 Limited Lens
Pentax

Pentax 21390 HD DA 40mm f/2.8 Limited Lens

★★★★★4.6 (93 reviews)
f/2.8

The Pentax HD DA 40mm f/2.8 Limited is an ultra-slim pancake lens delivering sharp optics in a remarkably pocketable design.

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Overview

The Pentax HD DA 40mm f/2.8 Limited is a pancake-style prime lens that exemplifies the "Limited" series philosophy of combining premium optics with compact, beautifully crafted hardware. At just 40mm on APS-C Pentax bodies—equivalent to roughly 60mm in full-frame terms—it sits in a versatile standard focal range suitable for street photography, everyday shooting, and casual portraiture. Its ultra-thin profile barely adds any depth to the camera body, making the entire system pocketable in a way that few interchangeable-lens setups can match.

Despite its diminutive size, the HD DA 40mm f/2.8 does not compromise on image quality. The HD (High-Definition) multi-layer coating minimizes internal reflections and flare, producing images with strong contrast and accurate color rendition. A 9-blade diaphragm smooths out the bokeh in out-of-focus areas, and the Quick-Shift Focus System lets photographers override autofocus with a simple turn of the focus ring for precise manual control. For Pentax shooters seeking a lens they can leave on the camera all day without fatigue, the HD DA 40mm f/2.8 Limited is a compelling and characterful choice.

Key Features

Standard, 40mm focal length (60mm in 35mm film format)

Ultra-thin, pancake design, available in two colors

9 blade diaphragm for stunning bokeh

Quick-Shift Focus System

Unique super-compact design in two colors

Specifications

Brand
Pentax
Model
21390
Mount
Pentax KAF
Focal Length
40mm (60mm equivalent on APS-C)
Maximum Aperture
f/2.8
Lens Design
Ultra-Thin Pancake
Coating
HD (High-Definition) Multi-Layer
Diaphragm Blades
9
Focus System
Quick-Shift Focus System
Zoom
No (Fixed Prime)
Color
Limited Black
ASIN
B00EZJPU0M

Pros & Cons

👍 Pros

  • Extremely compact pancake design makes the camera system highly portable and discreet
  • HD multi-layer coating delivers excellent contrast, color accuracy, and flare resistance
  • 9-blade diaphragm produces smooth, attractive bokeh for a lens of this size
  • Quick-Shift Focus System allows seamless transition from autofocus to manual focus
  • Limited series build quality with premium materials and precise construction

👎 Cons

  • Fixed f/2.8 maximum aperture is slower than competing 40mm primes from other systems
  • No weather sealing mentioned, limiting confidence in challenging outdoor conditions
  • Pentax K-mount limits compatibility to Pentax and Ricoh DSLR bodies only
  • Autofocus motor may be slower than ultrasonic systems found in competing lenses

Frequently Asked Questions

It features an ultra-thin pancake design that makes it one of the slimmest autofocus lenses available for the Pentax K-mount system, barely protruding from the camera body.
On Pentax APS-C cameras, the 40mm focal length provides an equivalent field of view of approximately 60mm in 35mm film format, making it a versatile standard-to-short-telephoto perspective.
Yes, the HD DA 40mm f/2.8 features Pentax's Quick-Shift Focus System, which allows you to instantly switch from autofocus to manual focus by simply turning the focus ring after the AF locks.
No, this is a fixed focal length (prime) lens at 40mm. It does not zoom, but prime lenses typically offer superior sharpness and a wider maximum aperture than zoom lenses at a comparable size.
HD stands for High-Definition coating, Pentax's advanced multi-layer lens coating that reduces reflections and flare more effectively than standard coatings, resulting in improved contrast and color accuracy.

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