Pentax smc Pentax-DA 40mm f/2.8 Limited Specs & DoF

40 mm

Focal length

f/2.8

Maximum aperture

39°

Diagonal angle of view (APS-C)

APS-C

Designed for

Specifications#

Brand: Pentax
Model: smc Pentax-DA 40mm f/2.8 Limited
Lens type: Standard prime
Focal length: 40 mm
Maximum aperture: f/2.8
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 40 mm	Equiv. aperture (DoF)
APS-C	60 mm · 39°	f/4.2
APS-C (Canon)	64 mm · 37°	f/4.5
Micro Four Thirds	80 mm · 30°	f/5.6

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: 40 mm f/2.8 on aps-c.

Focal	Aperture	at 1 m	at 2 m	at 5 m	at 10 m	Hyperfocal	Blur @2 m
40 mm	f/2.8	6.6 cm	27.0 cm	1.75 m	7.71 m	29.3 m	1.2%
40 mm	f/4	9.4 cm	38.7 cm	2.58 m	12.8 m	20.5 m	0.9%
40 mm	f/8	18.9 cm	79.6 cm	6.34 m	379 m	10.3 m	0.4%

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 40 mm	NPF at 40 mm, f/2.8
APS-C	1/60 s	8 s	5 s
APS-C (Canon)	1/60 s	8 s	5 s
Micro Four Thirds	1/80 s	6 s	5 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 smc Pentax-DA 40mm f/2.8 XS f/2.8
Pentax smc Pentax-FA 43mm f/1.9 Limited f/1.9
Pentax smc Pentax-DA 35mm f/2.4 AL f/2.4
Pentax smc Pentax-M 35mm 1:2 f/2
Sigma 35mm f/1.4 DG HSM | A f/1.4
Zeiss Carl Zeiss Distagon T* 2/35 ZF.2 f/2
Pentax smc Pentax-A 50mm f/1.4 f/1.4
Pentax smc Pentax-A 50mm f/1.7 f/1.7
Pentax smc Pentax-FA 50mm f/1.4 f/1.4
Pentax smc Pentax-FA 50mm f/1.7 f/1.7
Pentax smc Pentax-M 50mm f/1.4 f/1.4
Pentax smc Pentax-M 50mm f/1.7 f/1.7

Frequently asked questions#

Is the Pentax smc Pentax-DA 40mm f/2.8 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 40mm f/2.8 Limited equivalent to on APS-C?

Its focal length is already the real value for APS-C: 40 mm frames like 61 mm on full frame.

What is the Pentax smc Pentax-DA 40mm f/2.8 Limited good for?

As a standard prime it suits street, documentary, everyday and low-light shooting.

Sources & licences#

Lensfun lens database — CC BY-SA 3.0