Pentax smc Pentax-DA 17-70mm f/4 AL [IF] SDM Specs & DoF

17–70 mm

Focal length

f/4

Maximum aperture

79°–23°

Diagonal angle of view (APS-C)

APS-C

Designed for

4.1×

Zoom ratio

Specifications#

Brand: Pentax
Model: smc Pentax-DA 17-70mm f/4 AL [IF] SDM
Lens type: Standard zoom
Focal length: 17–70 mm
Maximum aperture: f/4
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 17 mm	At 34 mm	At 70 mm	Equiv. aperture (DoF)
APS-C	26 mm · 79°	51 mm · 45°	105 mm · 23°	f/6.0
APS-C (Canon)	27 mm · 77°	54 mm · 43°	112 mm · 22°	f/6.4
Micro Four Thirds	34 mm · 65°	68 mm · 35°	140 mm · 18°	f/8.0

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: 16 mm f/4 on aps-c.

Focal	Aperture	at 1 m	at 2 m	at 5 m	at 10 m	Hyperfocal	Blur @2 m
17 mm	f/4	57.3 cm	3.02 m	∞	∞	3.71 m	0.2%
17 mm	f/8	1.48 m	∞	∞	∞	1.86 m	0.1%
34 mm	f/4	13.1 cm	54.2 cm	3.79 m	24.7 m	14.8 m	0.6%
34 mm	f/8	26.6 cm	1.15 m	12.3 m	∞	7.42 m	0.3%
70 mm	f/4	3.0 cm	12.3 cm	79.2 cm	3.25 m	62.7 m	2.7%
70 mm	f/8	5.9 cm	24.7 cm	1.61 m	7.05 m	31.4 m	1.4%

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 17 mm	NPF at 17 mm, f/4
APS-C	1/100 s	20 s	15 s
APS-C (Canon)	1/125 s	18 s	15 s
Micro Four Thirds	1/125 s	15 s	14 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#

Sigma 17-50mm f/2.8 EX DC HSM f/2.8
Sigma 17-50mm f/2.8 EX DC OS HSM f/2.8
Tamron AF 17-50mm f/2.8 XR Di-II LD (Model A16) f/2.8
Tamron SP AF 17-50mm f/2.8 XR Di II LD Aspherical (IF) f/2.8
Pentax HD Pentax-DA 18-50mm f/4-5.6 DC WR RE f/4–5.6
Pentax smc Pentax-DA 18-55mm f/3.5-5.6 AL f/3.5–5.6
Pentax smc Pentax-DA 18-55mm f/3.5-5.6 AL II/L/WR f/3.5–5.6
Pentax smc Pentax-DA L 18-50mm f/4-5.6 DC WR RE f/4–5.6
Sigma 18-125mm f/3.5-5.6 DC f/3.5–5.6
Sigma 18-35mm f/1.8 DC HSM [A] f/1.8
Sigma 18-50mm f/2.8 EX DC f/2.8
Sigma 18-50mm f/3.5-5.6 DC f/3.5–5.6

Frequently asked questions#

Is the Pentax smc Pentax-DA 17-70mm f/4 AL [IF] SDM 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 17-70mm f/4 AL [IF] SDM equivalent to on APS-C?

Its focal length is already the real value for APS-C: 17–70 mm frames like 26–107 mm on full frame.

What is the Pentax smc Pentax-DA 17-70mm f/4 AL [IF] SDM good for?

As a standard zoom it suits everyday shooting, travel, events and walkaround use.

Sources & licences#

Lensfun lens database — CC BY-SA 3.0