Ricoh Pentax K-3 Mark III Specs, Sensor Size & Crop Factor

Q: What is the crop factor of the Ricoh Pentax K-3 Mark III?

The Ricoh Pentax K-3 Mark III has a crop factor of 1.55× relative to 35 mm full frame (diagonal 28.0 mm vs 43.3 mm).

1.55×

Crop factor

23.3×15.5 mm

Sensor size

361 mm²

Area · 42% of full frame

25.7 MP

Resolution

3.76 µm

Pixel pitch

f/5.6

Diffraction-limited aperture

2021

Release year

Specifications#

Brand: Ricoh
Model: Pentax K-3 Mark III
Also known as: K-3 III
Camera type: DSLR
Released: 2021-04-23
Lens mount: Pentax K
Sensor size: 23.3 × 15.5 mm (APS-C)
Crop factor: 1.55×
Resolution: 25.7 MP (6,192 × 4,128 px)
ISO range: 100 – 1,600,000
Fastest shutter: 1/8,000 s
Continuous shooting: 12 fps
Max video resolution: 4K
Weight: 735 g (25.9 oz)
Sensor type: BSI-CMOS, without low-pass filter
Viewfinder: Optical (Pentaprism)
AF points / area: Auto Area, Select, Zone Select, Expanded Select Area (S, M or L), Select S, Spot.
Metering: TTL open aperture metering using 307.000 pixel RGB sensor
Exposure modes: Scene Analyze Auto, Manual (M), Aperture Priority (Av), Shutter Priority (Tv), Shutter and Aperture Priority (TAv), Sensitivity Priority (Sv), Flexible Program (P), Bulb (B), 5 User Modes
Shutter: Electronically controlled vertical-run focal plane shutter, Electronic Shutter.
Flash: External only: 1/200 X-sync speed, hot shoe for P-TTL flash units with high-speed sync support, X-sync socket
Battery: D-Li90P (body USB rechargeable)
Dimensions: 134.5 *
Lens: Interchangeable lens
Predecessor: Pentax K-3 II
Launch price: $1,900 USD
Drive: up to 12 fps for 37 JPG or 30 RAW images (11 fps with AF.C)
Video: 1920×1080 (60p/30p//24p）; 4K (30p/24p)

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

Sensor size compared#

The Ricoh Pentax K-3 Mark III sensor (highlighted) drawn to scale against common formats. Its area is 42% of a full-frame sensor, which collects about 1.3 stops less total light at the same exposure.

Focal length equivalents & field of view#

Multiply any focal length by 1.55 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	111.0°	88.2°	120.5°
10 mm	15 mm	98.7°	75.6°	108.9°
12 mm	19 mm	88.3°	65.7°	98.8°
14 mm	22 mm	79.5°	57.9°	90.0°
16 mm	25 mm	72.1°	51.7°	82.3°
18 mm	28 mm	65.8°	46.6°	75.7°
20 mm	31 mm	60.4°	42.4°	70.0°
24 mm	37 mm	51.8°	35.8°	60.5°
28 mm	43 mm	45.2°	30.9°	53.1°
35 mm	54 mm	36.8°	25.0°	43.6°
40 mm	62 mm	32.5°	21.9°	38.6°
50 mm	77 mm	26.2°	17.6°	31.3°
56 mm	87 mm	23.5°	15.8°	28.1°
70 mm	108 mm	18.9°	12.6°	22.6°
85 mm	131 mm	15.6°	10.4°	18.7°
100 mm	155 mm	13.3°	8.9°	15.9°
135 mm	209 mm	9.9°	6.6°	11.8°
200 mm	309 mm	6.7°	4.4°	8.0°
300 mm	464 mm	4.4°	3.0°	5.3°
400 mm	618 mm	3.3°	2.2°	4.0°
600 mm	928 mm	2.2°	1.5°	2.7°
800 mm	1237 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 19.4 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	8.7 cm	36.3 cm	1.62 m	4.45 m	42.2 m	∞	5.63 m
14 mm	f/2.8	13.7 cm	59.1 cm	3.16 m	15.8 m	∞	∞	3.62 m
14 mm	f/4	20.0 cm	92.1 cm	8.25 m	∞	∞	∞	2.54 m
14 mm	f/8	45.2 cm	4.00 m	∞	∞	∞	∞	1.28 m
28 mm	f/1.8	2.1 cm	8.7 cm	35.4 cm	80.9 cm	2.33 m	11.1 m	22.5 m
28 mm	f/2.8	3.3 cm	13.5 cm	55.7 cm	1.29 m	3.91 m	26.5 m	14.5 m
28 mm	f/4	4.7 cm	19.4 cm	81.2 cm	1.93 m	6.50 m	777 m	10.1 m
28 mm	f/8	9.4 cm	40.0 cm	1.84 m	5.40 m	319 m	∞	5.08 m
48 mm	f/1.8	0.7 cm	2.9 cm	11.8 cm	26.9 cm	75.5 cm	3.09 m	66.0 m
48 mm	f/2.8	1.1 cm	4.5 cm	18.5 cm	42.0 cm	1.18 m	4.97 m	42.5 m
48 mm	f/4	1.5 cm	6.4 cm	26.4 cm	60.3 cm	1.72 m	7.55 m	29.7 m
48 mm	f/8	3.0 cm	12.9 cm	53.5 cm	1.24 m	3.75 m	24.4 m	14.9 m
78 mm	f/1.8	0.2 cm	1.1 cm	4.4 cm	10.1 cm	28.3 cm	1.14 m	174 m
78 mm	f/2.8	0.4 cm	1.6 cm	6.9 cm	15.7 cm	44.0 cm	1.79 m	112 m
78 mm	f/4	0.5 cm	2.4 cm	9.8 cm	22.4 cm	63.0 cm	2.57 m	78.5 m
78 mm	f/8	1.1 cm	4.7 cm	19.7 cm	45.0 cm	1.28 m	5.41 m	39.3 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/1.9	33.7 m
f/1.4	f/2.2	28.9 m
f/1.8	f/2.8	22.5 m
f/2	f/3.1	20.2 m
f/2.8	f/4.3	14.5 m
f/4	f/6.2	10.1 m
f/5.6	f/8.7	7.24 m
f/8	f/12.4	5.08 m

Diffraction & pixel pitch#

With 3.76 µm pixels, diffraction starts to soften pixel-level detail around f/5.6. For maximum sharpness keep landscapes between f/3.1 and f/6; stopping down further trades detail for depth of field.

Aperture	Airy disk diameter	Spread over	At 100% view
f/2.8	3.8 µm	1.0 px	sharp
f/4	5.4 µm	1.4 px	sharp
f/5.6	7.5 µm	2.0 px	sharp
f/8	10.7 µm	2.9 px	slight softening
f/11	14.8 µm	3.9 px	visibly soft
f/16	21.5 µm	5.7 px	visibly soft
f/22	29.5 µm	7.8 px	visibly soft

Maximum print sizes#

At 25.7 MP the Ricoh Pentax K-3 Mark III produces 6,192 × 4,128 pixel images. See the 26 megapixel guide or the print size calculator.

Resolution	Typical use	Inches	Centimetres
300 DPI	Photo-lab quality	20.6 × 13.8 in	52 × 35 cm
240 DPI	Fine-art inkjet	25.8 × 17.2 in	66 × 44 cm
200 DPI	Wall print	31.0 × 20.6 in	79 × 52 cm
150 DPI	Poster, viewed from 1 m+	41.3 × 27.5 in	105 × 70 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.)	35.9 s	19.5 s	23.4 s	28.1 s
13 mm (20 mm eq.)	24.9 s	13.5 s	16.2 s	19.5 s
16 mm (25 mm eq.)	20.2 s	11.0 s	13.2 s	15.8 s
23 mm (36 mm eq.)	14.1 s	7.6 s	9.2 s	11.0 s
32 mm (49 mm eq.)	10.1 s	5.5 s	6.6 s	7.9 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
32 mm	1/50 s	1/6 s	0.6 s
65 mm	1/100 s	1/13 s	0.3 s
129 mm	1/200 s	1/25 s	1/6 s

Lenses for the Ricoh Pentax K-3 Mark III#

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 Ricoh Pentax K-3 Mark III?

The Ricoh Pentax K-3 Mark III has a crop factor of 1.55× relative to 35 mm full frame (diagonal 28.0 mm vs 43.3 mm).

What size is the Ricoh Pentax K-3 Mark III sensor?

23.3 × 15.5 mm (APS-C), an area of 361 mm² — 42% of full frame.

Is the Ricoh Pentax K-3 Mark III full frame?

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

How many megapixels does the Ricoh Pentax K-3 Mark III have?

25.7 megapixels (6,192 × 4,128 pixels), enough for a 21 × 14 inch print at 300 DPI.

What lens mount does the Ricoh Pentax K-3 Mark III use?

The Ricoh Pentax K-3 Mark III uses the Pentax K (flange distance 45.46 mm).

How long can I expose the night sky with the Ricoh Pentax K-3 Mark III?

With a 13 mm lens (20 mm equivalent) the 500 rule gives 25 s and the stricter NPF rule at f/2.8 gives 16 s.

Sources & licences#

Wikipedia: Pentax K-3 Mark III — CC BY-SA 4.0
Wikidata Q106303442 — CC0
Lensfun camera database — CC BY-SA 3.0

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