Pentax smc Pentax-DA 21mm f/3.2 AL Limited Specs & DoF

21 mm

Focal length

f/3.2

Maximum aperture

68°

Diagonal angle of view (APS-C)

APS-C

Designed for

Specifications#

Brand: Pentax
Model: smc Pentax-DA 21mm f/3.2 AL Limited
Lens type: Wide-angle prime
Focal length: 21 mm
Maximum aperture: f/3.2
Image circle: APS-C (23.5×15.6 mm)
Mount(s): Pentax K
Projection: Rectilinear
Lensfun correction profile: Yes — distortion/vignetting/TCA

Equivalent focal length on different cameras#

Field of view and depth-of-field equivalence when this lens is used on bodies with different sensor sizes (natively or via an adapter).

Camera format	At 21 mm	Equiv. aperture (DoF)
APS-C	32 mm · 68°	f/4.8
APS-C (Canon)	34 mm · 65°	f/5.1
Micro Four Thirds	42 mm · 55°	f/6.4

Depth of field & background blur#

Computed on its native APS-C format (CoC 20 µm). “Blur @2 m” is the size of an out-of-focus point at infinity, as a percentage of frame width, with the subject at 2 m — a simple bokeh index. Full table: 20 mm f/4 on aps-c.

Focal	Aperture	at 1 m	at 2 m	at 5 m	at 10 m	Hyperfocal	Blur @2 m
21 mm	f/3.2	28.3 cm	1.22 m	14.1 m	∞	7.07 m	0.3%
21 mm	f/4	35.8 cm	1.60 m	40.2 m	∞	5.66 m	0.2%
21 mm	f/8	79.0 cm	5.54 m	∞	∞	2.84 m	0.1%

Handheld & night-sky limits#

NPF assumes typical 20–24 MP sensors (≈6 µm pixels on full frame, ≈3.9 µm on APS-C, ≈3.3 µm on Micro Four Thirds).

Body	Min. handheld shutter (longest focal)	500 rule at 21 mm	NPF at 21 mm, f/3.2
APS-C	1/30 s	16 s	11 s
APS-C (Canon)	1/30 s	15 s	11 s
Micro Four Thirds	1/40 s	12 s	10 s

Compatible cameras#

Bodies in our database with a native Pentax K mount. Full-frame bodies switch to an APS-C crop with this lens.

Adapt it to other systems#

Sony E-mount Canon RF Nikon Z Fujifilm X-mount Micro Four Thirds L-Mount Canon EF-M Fujifilm G-mount Hasselblad XCD Nikon 1 (CX)Pentax Q Samsung NX Canon EF Nikon F

Similar lenses#

Pentax HD Pentax-DA 21mm f/3.2 ED AL Limited f/3.2
Samyang 24mm f/1.4 ED AS IF UMC f/1.4
Samyang T-S 24mm f/3.5 ED AS UMC f/3.5
Sigma 24mm f/2.8 Super Wide II f/2.8
Zeiss Distagon T* 25mm f/2.8 ZF.2 f/2.8
Pentax smc Pentax-A 28mm 1:2.8 f/2.8
Pentax smc Pentax-F 28mm f/2.8 f/2.8
Pentax smc Pentax-FA 28mm f/2.8 AL f/2.8
Pentax smc Pentax-M 28mm 1:3.5 f/3.5
Pentax smc Pentax-M 28mm f/2.8 f/2.8
Sigma 28mm f/1.8 EX DG f/1.8
Pentax smc Pentax-DA 15mm f/4 ED AL Limited f/4

Frequently asked questions#

Is the Pentax smc Pentax-DA 21mm f/3.2 AL Limited full frame?

No — it is designed for APS-C sensors. On a full-frame body it vignettes or triggers crop mode.

What is the Pentax smc Pentax-DA 21mm f/3.2 AL Limited equivalent to on APS-C?

Its focal length is already the real value for APS-C: 21 mm frames like 32 mm on full frame.

What is the Pentax smc Pentax-DA 21mm f/3.2 AL Limited good for?

As a wide-angle prime it suits street, environmental portraits, landscapes and astro.

Sources & licences#

Lensfun lens database — CC BY-SA 3.0