Pentax Takumar 135mm f/2.5 Bayonet Specs & DoF

135 mm

Focal length

f/2.5

Maximum aperture

18°

Diagonal angle of view (Full frame)

Full frame

Designed for

Specifications#

Brand: Pentax
Model: Takumar 135mm f/2.5 Bayonet
Lens type: Portrait / short tele prime
Focal length: 135 mm
Maximum aperture: f/2.5
Image circle: Full frame (36×24 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 135 mm	Equiv. aperture (DoF)
Full frame	135 mm · 18°	f/2.5
APS-C	202 mm · 12°	f/3.8
APS-C (Canon)	216 mm · 11°	f/4.0
Micro Four Thirds	270 mm · 9°	f/5.0

Depth of field & background blur#

Computed on its native Full frame format (CoC 30 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: 135 mm f/2.8 on full frame.

Focal	Aperture	at 1 m	at 2 m	at 5 m	at 10 m	Hyperfocal	Blur @2 m
135 mm	f/2.5	0.7 cm	3.1 cm	20.0 cm	81.3 cm	243 m	10.9%
135 mm	f/4	1.1 cm	4.9 cm	32.1 cm	1.30 m	152 m	6.8%
135 mm	f/8	2.3 cm	9.8 cm	64.3 cm	2.64 m	76.1 m	3.4%

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 135 mm	NPF at 135 mm, f/2.5
Full frame	1/125 s	4 s	2 s
APS-C	1/200 s	2 s	2 s
APS-C (Canon)	1/200 s	2 s	1 s
Micro Four Thirds	1/250 s	2 s	1 s

Compatible cameras#

Bodies in our database with a native Pentax K mount.

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#

Samyang 135mm f/2 ED UMC f/2
Pentax smc Pentax-M 135mm f/3.5 f/3.5
Samyang 85mm f/1.4 IF UMC Aspherical f/1.4
Sigma 85mm f/1.4 EX DG HSM f/1.4
Pentax smc Pentax-FA 77mm f/1.8 Limited f/1.8
Pentax HD Pentax-DA 70mm f/2.4 Limited f/2.4
Pentax smc Pentax-DA 70mm f/2.4 Limited f/2.4
Pentax smc Pentax-DA* 55mm f/1.4 SDM f/1.4
Pentax smc Pentax-DA 50mm f/1.8 f/1.8

Frequently asked questions#

Is the Pentax Takumar 135mm f/2.5 Bayonet full frame?

Yes — it covers the full 36 × 24 mm frame.

What is the Pentax Takumar 135mm f/2.5 Bayonet equivalent to on APS-C?

On a 1.5× APS-C body it frames like 202 mm, and like 216 mm on Canon APS-C.

What is the Pentax Takumar 135mm f/2.5 Bayonet good for?

As a portrait / short tele prime it suits head-and-shoulders portraits with flattering perspective and creamy backgrounds.

Sources & licences#

Lensfun lens database — CC BY-SA 3.0