Pentax K20D Specs, Sensor Size & Crop Factor

Q: What is the crop factor of the Pentax K20D?

The Pentax K20D has a crop factor of 1.54× relative to 35 mm full frame (diagonal 28.1 mm vs 43.3 mm).

1.54×

Crop factor

23.4×15.6 mm

Sensor size

366 mm²

Area · 42% of full frame

14.6 MP

Resolution

5.00 µm

Pixel pitch

f/7.5

Diffraction-limited aperture

2008

Release year

Specifications#

Brand: Pentax
Model: K20D
Camera type: DSLR
Released: 2008-01-01
Lens mount: Pentax K
Sensor size: 23.4 × 15.6 mm (APS-C)
Crop factor: 1.54×
Resolution: 14.6 MP (4,677 × 3,121 px)
Weight: 715 g (25.2 oz)
Sensor: CMOS active pixel sensor with a primary color filter
Metering: TTL open-aperture metering with choice of: 16-segment, center-weighted & spot meter
Exposure modes: Program, Sensitivity Priority, Shutter-Speed Priority, Aperture Priority, Shutter-Speed and Aperture Priority, Manual, Bulb
Battery: Rechargeable D-LI50 Lithium-ion battery, Optional AC adapter
Lens: Interchangeable Pentax KAF2 mount compatible with Pentax auto-aperture lenses; older lenses supported in stop-down metering mode.

Specifications merged from Wikipedia, Wikidata, Lensfun and openMVG. Spot an error? Tell us.

Sensor size compared#

The Pentax K20D sensor (highlighted) drawn to scale against common formats. Its area is 42% of a full-frame sensor, which collects about 1.2 stops less total light at the same exposure.

Focal length equivalents & field of view#

Multiply any focal length by 1.54 to get the full-frame field of view. Angles are for a rectilinear lens focused at infinity.

Lens on this camera	Full-frame equivalent	Horizontal	Vertical	Diagonal
8 mm	12 mm	111.3°	88.6°	120.7°
10 mm	15 mm	99.0°	76.0°	109.2°
12 mm	18 mm	88.5°	66.1°	99.1°
14 mm	22 mm	79.8°	58.3°	90.3°
16 mm	25 mm	72.4°	52.0°	82.6°
18 mm	28 mm	66.0°	46.9°	76.0°
20 mm	31 mm	60.7°	42.7°	70.2°
24 mm	37 mm	52.0°	36.1°	60.8°
28 mm	43 mm	45.4°	31.2°	53.3°
35 mm	54 mm	37.0°	25.2°	43.8°
40 mm	62 mm	32.6°	22.1°	38.8°
50 mm	77 mm	26.3°	17.8°	31.4°
56 mm	86 mm	23.6°	15.9°	28.2°
70 mm	108 mm	19.0°	12.7°	22.7°
85 mm	131 mm	15.7°	10.5°	18.8°
100 mm	154 mm	13.3°	8.9°	16.0°
135 mm	208 mm	9.9°	6.6°	11.9°
200 mm	308 mm	6.7°	4.5°	8.0°
300 mm	461 mm	4.5°	3.0°	5.4°
400 mm	615 mm	3.4°	2.2°	4.0°
600 mm	923 mm	2.2°	1.5°	2.7°
800 mm	1230 mm	1.7°	1.1°	2.0°

Depth of field table#

Total depth of field at each subject distance, using a circle of confusion of 19.5 µm (the 0.030 mm full-frame standard scaled by the crop factor). Detailed tables: 24 mm f/1.8, 24 mm f/2.8, 35 mm f/1.8, 35 mm f/2.8, 50 mm f/1.8, 50 mm f/2.8.

Focal	Aperture	50.0 cm	1.00 m	2.00 m	3.00 m	5.00 m	10.0 m	Hyperfocal
14 mm	f/1.8	8.8 cm	36.5 cm	1.63 m	4.50 m	44.2 m	∞	5.60 m
14 mm	f/2.8	13.8 cm	59.4 cm	3.19 m	16.2 m	∞	∞	3.60 m
14 mm	f/4	20.1 cm	92.8 cm	8.44 m	∞	∞	∞	2.53 m
14 mm	f/8	45.5 cm	4.09 m	∞	∞	∞	∞	1.27 m
28 mm	f/1.8	2.1 cm	8.7 cm	35.6 cm	81.3 cm	2.34 m	11.2 m	22.4 m
28 mm	f/2.8	3.3 cm	13.6 cm	56.0 cm	1.30 m	3.94 m	26.9 m	14.4 m
28 mm	f/4	4.7 cm	19.5 cm	81.7 cm	1.94 m	6.55 m	1.3 km	10.1 m
28 mm	f/8	9.5 cm	40.2 cm	1.86 m	5.46 m	484 m	∞	5.05 m
48 mm	f/1.8	0.7 cm	2.9 cm	11.9 cm	27.0 cm	75.9 cm	3.10 m	65.7 m
48 mm	f/2.8	1.1 cm	4.5 cm	18.6 cm	42.2 cm	1.19 m	5.00 m	42.2 m
48 mm	f/4	1.5 cm	6.5 cm	26.6 cm	60.6 cm	1.73 m	7.60 m	29.6 m
48 mm	f/8	3.1 cm	13.0 cm	53.8 cm	1.25 m	3.78 m	24.7 m	14.8 m
78 mm	f/1.8	0.2 cm	1.1 cm	4.4 cm	10.1 cm	28.4 cm	1.15 m	173 m
78 mm	f/2.8	0.4 cm	1.7 cm	6.9 cm	15.8 cm	44.3 cm	1.80 m	111 m
78 mm	f/4	0.5 cm	2.4 cm	9.9 cm	22.5 cm	63.4 cm	2.59 m	78.0 m
78 mm	f/8	1.1 cm	4.7 cm	19.8 cm	45.2 cm	1.28 m	5.44 m	39.1 m

Equivalent aperture#

Exposure is identical at the same f-number on any format; equivalence only describes depth of field and total light.

Aperture on this camera	Full-frame equivalent (depth of field)	Hyperfocal at 28 mm
f/1.2	f/1.8	33.5 m
f/1.4	f/2.2	28.7 m
f/1.8	f/2.8	22.4 m
f/2	f/3.1	20.1 m
f/2.8	f/4.3	14.4 m
f/4	f/6.2	10.1 m
f/5.6	f/8.6	7.20 m
f/8	f/12.3	5.05 m

Diffraction & pixel pitch#

With 5.00 µm pixels, diffraction starts to soften pixel-level detail around f/7.5. For maximum sharpness keep landscapes between f/4.1 and f/7; stopping down further trades detail for depth of field.

Aperture	Airy disk diameter	Spread over	At 100% view
f/2.8	3.8 µm	0.8 px	sharp
f/4	5.4 µm	1.1 px	sharp
f/5.6	7.5 µm	1.5 px	sharp
f/8	10.7 µm	2.1 px	slight softening
f/11	14.8 µm	3.0 px	slight softening
f/16	21.5 µm	4.3 px	visibly soft
f/22	29.5 µm	5.9 px	visibly soft

Maximum print sizes#

At 14.6 MP the Pentax K20D produces 4,677 × 3,121 pixel images. See the 14 megapixel guide or the print size calculator.

Resolution	Typical use	Inches	Centimetres
300 DPI	Photo-lab quality	15.6 × 10.4 in	40 × 26 cm
240 DPI	Fine-art inkjet	19.5 × 13.0 in	49 × 33 cm
200 DPI	Wall print	23.4 × 15.6 in	59 × 40 cm
150 DPI	Poster, viewed from 1 m+	31.2 × 20.8 in	79 × 53 cm

Night-sky exposure limits#

Longest exposure before stars trail. The NPF rule accounts for pixel pitch and is stricter than the classic 500 rule — use it for pin-sharp stars on high-resolution sensors.

Focal length	500 rule	NPF f/1.8	NPF f/2.8	NPF f/4
9 mm (14 mm eq.)	36.1 s	23.7 s	27.6 s	32.2 s
13 mm (20 mm eq.)	25.0 s	16.4 s	19.1 s	22.3 s
16 mm (25 mm eq.)	20.3 s	13.3 s	15.5 s	18.1 s
23 mm (35 mm eq.)	14.1 s	9.3 s	10.8 s	12.6 s
33 mm (51 mm eq.)	9.9 s	6.5 s	7.5 s	8.8 s

Open the NPF / 500 rule calculator →

Handheld shutter speed guide#

The reciprocal rule uses the equivalent focal length. High-resolution sensors may need one stop faster than this for pixel-sharp results.

Focal length	No stabilisation (1/equiv. focal)	With 3-stop IS	With 5-stop IBIS
16 mm	1/25 s	0.3 s	1.3 s
33 mm	1/50 s	1/6 s	0.6 s
65 mm	1/100 s	1/13 s	0.3 s
130 mm	1/200 s	1/25 s	1/6 s

Lenses for the Pentax K20D#

Native Pentax K lenses in our database (170 total). Also adaptable: T-mount (T2), M42 screw mount, Deckel (DKL), Tamron Adaptall, M39 / LTM (Leica thread).

Samyang 8mm f/3.5 Fish-Eye CS 8 mm
Samyang 10mm f/2.8 ED AS NCS CS 10 mm
Laowa 12mm f/2.8 Zero-D 12 mm
Samyang 14mm f/2.8 AE ED AS IF UMC 14 mm
Laowa 15mm F/4 Wide Angle Macro 15 mm
Samyang 16mm f/2.0 ED AS UMC CS 16 mm
Samyang 20mm f/1.8 ED AS UMC 20 mm
Samyang 24mm f/1.4 ED AS IF UMC 24 mm
Samyang T-S 24mm f/3.5 ED AS UMC 24 mm
Laowa 60mm f/2.8 2X Ultra-Macro 60 mm
Samyang 85mm f/1.4 IF UMC Aspherical 85 mm
Samyang 135mm f/2 ED UMC 135 mm
Sigma 4.5mm f/2.8 EX DC HSM circular fisheye 4.5 mm
Sigma 8-16mm f/4.5-5.6 DC HSM 8–16 mm
Pentax smc Pentax-DA Fish-Eye 10-17mm f/3.5-4.5 ED IF 10–17 mm
Sigma 10-20mm f/3.5 EX DC HSM 10–20 mm
Sigma 10-20mm f/4-5.6 EX DC 10–20 mm
Sigma 10mm f/2.8 EX DC Fisheye HSM 10 mm
Tamron SP AF 10-24mm f/3.5-4.5 Di II LD Aspherical (IF) 10–24 mm
Pentax HD Pentax-DA* 11-18mm f/2.8 ED DC AW 11–18 mm
Tamron SP AF 11-18mm f/4.5-5.6 Di-II LD Aspherical (IF) 11–18 mm
Pentax smc Pentax-DA 12-24mm f/4 ED AL IF 12–24 mm
Sigma 12-24mm F4.5-5.6 II DG HSM 12–24 mm
Sigma 12-24mm f/4.5-5.6 EX DG Aspherical HSM 12–24 mm
Pentax smc PENTAX-DA 14mm F2.8 ED[IF] 14 mm
Sigma 14mm f/2.8 EX 14 mm
Sigma 14mm f/2.8 EX Aspherical HSM 14 mm
Sigma 14mm f/3.5 EX 14 mm
Pentax HD Pentax-D FA 15-30mm f/2.8 ED SDM WR 15–30 mm
Pentax smc Pentax-DA 15mm f/4 ED AL Limited 15 mm
Sigma 15-30mm f/3.5-4.5 EX DG Aspherical 15–30 mm
Sigma 15mm f/2.8 EX DG Diagonal Fisheye 15 mm
Pentax HD Pentax DA* 16-50mm f/2.8 ED PLM AW 16–50 mm
Pentax HD Pentax-DA 16-85mm f/3.5-5.6 ED DC WR 16–85 mm
Pentax smc Pentax-DA 16-45mm f/4 ED AL 16–45 mm
Pentax smc Pentax-DA* 16-50mm f/2.8 ED AL IF SDM 16–50 mm

Similar cameras#

Other APS-C cameras from around the same time.

Frequently asked questions#

What is the crop factor of the Pentax K20D?

The Pentax K20D has a crop factor of 1.54× relative to 35 mm full frame (diagonal 28.1 mm vs 43.3 mm).

What size is the Pentax K20D sensor?

23.4 × 15.6 mm (APS-C), an area of 366 mm² — 42% of full frame.

Is the Pentax K20D full frame?

No — its sensor is APS-C, which is 2.4× smaller in area than full frame.

How many megapixels does the Pentax K20D have?

14.6 megapixels (4,677 × 3,121 pixels), enough for a 16 × 10 inch print at 300 DPI.

What lens mount does the Pentax K20D use?

The Pentax K20D uses the Pentax K (flange distance 45.46 mm).

How long can I expose the night sky with the Pentax K20D?

With a 13 mm lens (20 mm equivalent) the 500 rule gives 25 s and the stricter NPF rule at f/2.8 gives 19 s.

Sources & licences#

Last updated October 03, 2026 · How we calculate · Sources