Pentax K-3 III vs K-S2

The Pentax K-3 III and the Pentax K-S2 are two digital cameras that were announced, respectively, in March 2021 and February 2015. Both are DSLR (Digital Single Lens Reflex) cameras that are equipped with an APS-C sensor. The K-3 III has a resolution of 25.6 megapixels, whereas the K-S2 provides 20 MP.

Below is an overview of the main specs of the two cameras as a starting point for the comparison.

Headline Specifications

Pentax K-3 III		Pentax K-S2
Digital single lens reflex		Digital single lens reflex
Pentax K mount lenses		Pentax K mount lenses
25.6 MP – APS-C sensor		20 MP – APS-C sensor
4K/30p Video		1080/30p Video
ISO 100-160,000		ISO 100-51,200
Optical viewfinder		Optical viewfinder
3.2" LCD – 1620k dots		3.0" LCD – 921k dots
Fixed touchscreen		Swivel screen (not touch-sensitive)
12 shutter flaps per second		5.4 shutter flaps per second
In-body stabilization		In-body stabilization
Weathersealed body		Weathersealed body
800 shots per battery charge		410 shots per battery charge
135 x 104 x 74 mm, 820 g		123 x 91 x 73 mm, 678 g

Check K-3 III price at
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Check K-S2 offers at
ebay.com

Going beyond this snapshot of core features and characteristics, what are the differences between the Pentax K-3 III and the Pentax K-S2? Which one should you buy? Read on to find out how these two cameras compare with respect to their body size, their imaging sensors, their shooting features, their input-output connections, and their reception by expert reviewers.

Body comparison

The physical size and weight of the Pentax K-3 III and the Pentax K-S2 are illustrated in the side-by-side display below. The two cameras are presented according to their relative size. Three successive views from the front, the top, and the rear are shown. All size dimensions are rounded to the nearest millimeter.

The K-3 III can be obtained in two different colors (black, silver), while the K-S2 is available in six color-versions (black, grey, pink, orange, green, white).

If the front view area (width x height) of the cameras is taken as an aggregate measure of their size, the Pentax K-S2 is notably smaller (20 percent) than the Pentax K-3 III. Moreover, the K-S2 is markedly lighter (17 percent) than the K-3 III. In this context, it is worth noting that both cameras are splash and dust-proof and can, hence, be used in inclement weather conditions or harsh environments.

The above size and weight comparisons are to some extent incomplete since they do not consider the interchangeable lenses that both of these cameras require. Hence, you might want to study and compare the specifications of available lenses in order to get the full picture of the size and weight of the two camera systems.

Concerning battery life, the K-3 III gets 800 shots out of its Pentax D-LI90 battery, while the K-S2 can take 410 images on a single charge of its Pentax D-LI109 power pack.

The table below summarizes the key physical specs of the two cameras alongside a broader set of comparators. If you would like to visualize and compare a different camera combination, you can navigate to the CAM-parator app and make your selection from a broad list of cameras there.

Body Specifications

		Camera Model	Camera Width	Camera Height	Camera Depth	Camera Weight	Battery Life	Weather Sealing	Camera Launch	Launch Price (USD)	Street Price
1.		Pentax K-3 III	135 mm	104 mm	74 mm	820 g	800	Y	Mar 2021	1,999	amazon.com
2.		Pentax K-S2	123 mm	91 mm	73 mm	678 g	410	Y	Feb 2015	749	ebay.com
3.		Fujifilm X-H1	140 mm	97 mm	86 mm	673 g	310	Y	Feb 2018	1,899	ebay.com
4.		Nikon D780	144 mm	116 mm	76 mm	840 g	2260	Y	Jan 2020	2,299	amazon.com
5.		Nikon Z6	134 mm	101 mm	67 mm	675 g	310	Y	Aug 2018	1,999	ebay.com
6.		Nikon Z6 II	134 mm	101 mm	70 mm	705 g	410	Y	Oct 2020	1,999	amazon.com
7.		Panasonic GH6	138 mm	100 mm	100 mm	823 g	360	Y	Feb 2022	2,199	amazon.com
8.		Panasonic S5	133 mm	98 mm	82 mm	714 g	440	Y	Sep 2020	1,999	amazon.com
9.		Pentax K-3	131 mm	100 mm	77 mm	800 g	560	Y	Oct 2013	1,299	ebay.com
10.		Pentax K-3 II	131 mm	100 mm	77 mm	800 g	720	Y	Apr 2015	1,099	ebay.com
11.		Pentax K-70	126 mm	93 mm	74 mm	688 g	410	Y	Jun 2016	649	ebay.com
12.		Pentax KP	132 mm	101 mm	76 mm	703 g	390	Y	Jan 2017	1,099	ebay.com
13.		Pentax K-S1	121 mm	93 mm	70 mm	558 g	410	n	Aug 2014	749	ebay.com
Note: Measurements and pricing do not include easily detachable parts, such as add-on or interchangeable lenses or optional viewfinders.
Convert to Imperial

Any camera decision will naturally be influenced heavily by the price. The manufacturer’s suggested retail prices give an idea on the placement of the camera in the maker’s lineup and the broader market. The K-S2 was launched at a markedly lower price (by 63 percent) than the K-3 III, which puts it into a different market segment. Usually, retail prices stay at first close to the launch price, but after several months, discounts become available. Later in the product cycle and, in particular, when the replacement model is about to appear, further discounting and stock clearance sales often push the camera price considerably down.

Sensor comparison

The size of the sensor inside a digital camera is one of the key determinants of image quality. A large sensor will tend to have larger individual pixels that provide better low-light sensitivity, wider dynamic range, and richer color-depth than smaller pixel-units in a sensor of the same technological generation. Moreover, a large sensor camera will give the photographer more control over depth-of-field in the image and, thus, the ability to better isolate a subject from the background. On the downside, larger sensors are more costly to manufacture and tend to lead to bigger and heavier cameras and lenses.

Both cameras under consideration feature an APS-C sensor, but their sensors differ slightly in size. The sensor area in the K-S2 is 2 percent bigger. They nevertheless have the same format factor of 1.5. Both cameras have a native aspect ratio (sensor width to sensor height) of 3:2.

In terms of chip-set technology, the K-3 III uses a more advanced image processing engine (PRIME V) than the K-S2 (PRIME MII), with benefits for noise reduction, color accuracy, and processing speed.

Despite having a slightly smaller sensor, the Pentax K-3 III offers a higher resolution of 25.6 megapixels, compared with 20 MP of the Pentax K-S2. This megapixels advantage comes at the cost of a higher pixel density and a smaller size of the individual pixel (with a pixel pitch of 3.76μm versus 4.28μm for the K-S2). However, it should be noted that the K-3 III is much more recent (by 6 years and 1 month) than the K-S2, and its sensor will have benefitted from technological advances during this time that make it possible to gather light more efficiently. Coming back to sensor resolution, it should be mentioned that neither of the two cameras has an anti-alias filter installed, so they are able to capture all the detail the sensor resolves.

The resolution advantage of the Pentax K-3 III implies greater flexibility for cropping images or the possibility to print larger pictures. The maximum print size of the K-3 III for good quality output (200 dots per inch) amounts to 31 x 20.6 inches or 78.6 x 52.4 cm, for very good quality (250 dpi) 24.8 x 16.5 inches or 62.9 x 41.9 cm, and for excellent quality (300 dpi) 20.6 x 13.8 inches or 52.4 x 35 cm. The corresponding values for the Pentax K-S2 are 27.4 x 18.2 inches or 69.5 x 46.3 cm for good quality, 21.9 x 14.6 inches or 55.6 x 37.1 cm for very good quality, and 18.2 x 12.2 inches or 46.3 x 30.9 cm for excellent quality prints.

Unlike the K-S2, the K-3 III has the capacity to capture high quality composite images (YESMP) by combining multiple shots after shifting its sensor by miniscule distances. This multi-shot, pixel-shift mode is most suitable for photography of stationary objects (landscapes, studio scenes).

The Pentax K-3 III has a native sensitivity range from ISO 100 to ISO 160000. The corresponding ISO settings for the Pentax K-S2 are ISO 100 to ISO 51200 (no boost).

Technology-wise, both cameras are equipped with CMOS (Complementary Metal–Oxide–Semiconductor) sensors. Both cameras use a Bayer filter for capturing RGB colors on a square grid of photosensors. This arrangement is found in most digital cameras.

For many cameras, data on sensor performance has been reported by DXO Mark. This service assesses and scores the color depth ("DXO Portrait"), dynamic range ("DXO Landscape"), and low-light sensitivity ("DXO Sports") of camera sensors, and also publishes an overall camera score. The following table provides an overview of the physical sensor characteristics, as well as the sensor quality measurements for a selection of comparators.

Sensor Characteristics

		Camera Model	Sensor Class	Resolution (MP)	Horiz. Pixels	Vert. Pixels	Video Format	DXO Portrait	DXO Landscape	DXO Sports	DXO Overall
1.		Pentax K-3 III	APS-C	25.6	6192	4128	4K/30p	24.2	13.7	2083	85
2.		Pentax K-S2	APS-C	20.0	5472	3648	1080/30p	23.6	12.9	1514	79
3.		Fujifilm X-H1	APS-C	24.0	6000	4000	4K/30p	24.0	13.3	1806	82
4.		Nikon D780	Full Frame	24.3	6048	4024	4K/30p	25.3	14.3	2877	95
5.		Nikon Z6	Full Frame	24.3	6048	4024	4K/30p	25.3	14.3	3299	95
6.		Nikon Z6 II	Full Frame	24.3	6048	4024	4K/60p	25.0	14.4	3303	94
7.		Panasonic GH6	Four Thirds	25.0	5776	4336	5.7K/60p	23.4	13.4	1555	77
8.		Panasonic S5	Full Frame	24.0	6000	4000	4K/60p	25.1	14.5	2697	94
9.		Pentax K-3	APS-C	24.1	6016	4000	1080/60i	23.7	13.4	1216	80
10.		Pentax K-3 II	APS-C	24.1	6016	4000	1080/60i	23.6	13.6	1106	80
11.		Pentax K-70	APS-C	24.0	6000	4000	1080/60i	23.8	13.1	1639	80
12.		Pentax KP	APS-C	24.1	6016	4000	1080/60i	23.9	13.2	1699	81
13.		Pentax K-S1	APS-C	20.0	5472	3648	1080/30p	23.5	13.0	1061	78
Note: DXO values in italics represent estimates based on sensor size and age.

Many modern cameras are not only capable of taking still images, but also of capturing video footage. Both cameras under consideration are equipped with sensors that have a sufficiently high read-out speed for moving images, but the K-3 III provides a higher video resolution than the K-S2. It can shoot video footage at 4K/30p, while the K-S2 is limited to 1080/30p.

Feature comparison

Beyond body and sensor, cameras can and do differ across a range of features. The K-3 III and the K-S2 are similar in the sense that both have an optical viewfinder. The latter is useful for getting a clear image for framing even in brightly lit environments. The viewfinders of both cameras offer the same field of view (100%), but the viewfinder of the K-3 III has a higher magnification than the one of the K-S2 (0.70x vs 0.63x), so that the size of the image transmitted appears closer to the size seen with the naked human eye. The table below summarizes some of the other core capabilities of the Pentax K-3 III and Pentax K-S2 in connection with corresponding information for a sample of similar cameras.

Core Features

		Camera Model	Viewfinder (Type or 000 dots)	Control Panel (yes/no)	LCD Specifications (inch/000 dots)	LCD Attach- ment	Touch Screen (yes/no)	Max Shutter Speed *	Max Shutter Flaps *	Built-in Flash (yes/no)	Built-in Image Stab
1.		Pentax K-3 III	optical	Y	3.2 / 1620	fixed	Y	1/8000s	12.0/s	n	Y
2.		Pentax K-S2	optical	n	3.0 / 921	swivel	n	1/6000s	5.4/s	Y	Y
3.		Fujifilm X-H1	3690	Y	3.0 / 1040	full-flex	Y	1/8000s	14.0/s	n	Y
4.		Nikon D780	optical	Y	3.2 / 2359	tilting	Y	1/8000s	12.0/s	n	n
5.		Nikon Z6	3690	Y	3.2 / 2100	tilting	Y	1/8000s	12.0/s	n	Y
6.		Nikon Z6 II	3690	Y	3.2 / 2100	tilting	Y	1/8000s	14.0/s	n	Y
7.		Panasonic GH6	3680	n	3.0 / 1840	full-flex	Y	1/8000s	14.0/s	n	Y
8.		Panasonic S5	2360	n	3.0 / 1840	swivel	Y	1/8000s	7.0/s	n	Y
9.		Pentax K-3	optical	Y	3.2 / 1037	fixed	n	1/8000s	8.3/s	Y	Y
10.		Pentax K-3 II	optical	Y	3.2 / 1037	fixed	n	1/8000s	8.3/s	n	Y
11.		Pentax K-70	optical	n	3.0 / 921	swivel	n	1/6000s	6.0/s	Y	Y
12.		Pentax KP	optical	n	3.0 / 921	tilting	n	1/6000s	7.0/s	Y	Y
13.		Pentax K-S1	optical	n	3.0 / 921	fixed	n	1/6000s	5.4/s	Y	Y
Note: *) Information refers to the mechanical shutter, unless the camera only has an electronic one.

One feature that is present on the K-3 III, but is missing on the K-S2 is a top-level LCD. While being, of course, smaller than the rear screen, the control panel conveys some of the essential shooting information and can be convenient for quick and easy settings verification.

The Pentax K-3 III and the Pentax K-S2 both have an intervalometer built-in. This enables the photographer to capture time lapse sequences, such as flower blooming, a sunset or moon rise, without purchasing an external camera trigger and related software.

Concerning the storage of imaging data, both the K-3 III and the K-S2 write their files to SDXC cards. The K-3 III features dual card slots, which can be very useful in case a memory card fails. In contrast, the K-S2 only has one slot. The K-3 III supports UHS-II cards (on its first slot), while the K-S2 can use UHS-I cards.

Connectivity comparison

For some imaging applications, the extent to which a camera can communicate with its environment can be an important aspect in the camera decision process. The table below provides an overview of the connectivity of the Pentax K-3 III and Pentax K-S2 and, in particular, the interfaces the cameras (and selected comparators) provide for accessory control and data transfer.

Input-Output Connections

		Camera Model	Hotshoe Port	Internal Mic / Speaker	Microphone Port	Headphone Port	HDMI Port	USB Port	WiFi Support	NFC Support	Bluetooth Support
1.		Pentax K-3 III	Y	stereo / mono	Y	Y	micro	3.2	Y	-	Y
2.		Pentax K-S2	Y	mono / mono	Y	-	micro	2.0	Y	Y	-
3.		Fujifilm X-H1	Y	stereo / mono	Y	-	micro	3.0	Y	-	-
4.		Nikon D780	Y	stereo / mono	Y	Y	mini	3.1	Y	-	Y
5.		Nikon Z6	Y	stereo / mono	Y	Y	micro	3.1	Y	-	Y
6.		Nikon Z6 II	Y	stereo / mono	Y	Y	micro	3.2	Y	-	Y
7.		Panasonic GH6	Y	stereo / mono	Y	Y	full	3.2	Y	-	Y
8.		Panasonic S5	Y	stereo / mono	Y	Y	micro	3.2	Y	-	Y
9.		Pentax K-3	Y	mono / mono	Y	Y	mini	3.0	-	-	-
10.		Pentax K-3 II	Y	mono / mono	Y	Y	mini	3.0	-	-	-
11.		Pentax K-70	Y	stereo / mono	Y	-	mini	2.0	Y	-	-
12.		Pentax KP	Y	stereo / mono	Y	-	-	2.0	Y	-	-
13.		Pentax K-S1	Y	stereo / mono	-	-	micro	2.0	-	-	-

It is notable that the K-3 III has a headphone jack, which is not present on the K-S2 This port makes it possible to attach external headphones and monitor the quality of sound during the recording process.

Studio photographers will appreciate that the Pentax K-3 III (unlike the K-S2) features a PC Sync socket, so that professional strobe lights can be controlled by the camera.

Travel and landscape photographers will find it useful that the K-3 III has an internal geolocalization sensor and can record GPS coordinates in its EXIF data.

The K-3 III is a recent model that features in the current product line-up of Pentax. In contrast, the K-S2 has been discontinued (but can be found pre-owned on ebay). There has not been a direct replacement model for the K-S2 from Pentax. Further information on the features and operation of the K-3 III and K-S2 can be found, respectively, in the Pentax K-3 III Manual (free pdf) or the online Pentax K-S2 Manual.

Review summary

So what is the bottom line? Is there a clear favorite between the Pentax K-3 III and the Pentax K-S2? Which camera is better? Below is a summary of the relative strengths of each of the two contestants.

Reasons to prefer the Pentax K-3 III:

• More detail: Offers more megapixels (25.6 vs 20MP) with a 13% higher linear resolution.
• High quality composites: Can combine several shots after pixel-shifting its sensor.
• Better jpgs: Has a more modern image processing engine (PRIME V vs PRIME MII).
• Better video: Provides higher definition movie capture (4K/30p vs 1080/30p).
• Better sound control: Has a headphone port that enables audio monitoring while recording.
• Larger viewfinder image: Features a viewfinder with a higher magnification (0.70x vs 0.63x).
• Easier setting verification: Features an LCD display on top to control shooting parameters.
• Larger screen: Has a bigger rear LCD (3.2" vs 3.0") for image review and settings control.
• More detailed LCD: Has a higher resolution rear screen (1620k vs 921k dots).
• Fewer buttons to press: Is equipped with a touch-sensitive rear screen to facilitate handling.
• Faster shutter: Has higher mechanical shutter speed (1/8000s vs 1/6000s) to freeze action.
• Faster burst: Shoots at higher frequency (12 vs 5.4 flaps/sec) to capture the decisive moment.
• Longer lasting: Can take more shots (800 versus 410) on a single battery charge.
• Easier geotagging: Features an internal GPS sensor to log localization data.
• Faster data transfer: Supports a more advanced USB protocol (3.2 vs 2.0).
• Easier wireless transfer: Supports Bluetooth for image sharing without cables.
• Better studio light control: Has a PC Sync socket to connect to professional strobe lights.
• Greater peace of mind: Features a second card slot as a backup in case of memory card failure.
• Faster buffer clearing: Supports a more advanced SD data transfer standard (UHS-II vs UHS-I).
• More modern: Reflects 6 years and 1 month of technical progress since the K-S2 launch.

Advantages of the Pentax K-S2:

• More flexible LCD: Has a swivel screen for odd-angle shots in portrait or landscape orientation.
• More selfie-friendly: Has an articulated screen that can be turned to be front-facing.
• More compact: Is smaller (123x91mm vs 135x104mm) and will fit more readily into a bag.
• Less heavy: Has a lower weight (by 142g or 17 percent) and is thus easier to take along.
• Easier fill-in: Has a small integrated flash to brighten shadows of backlit subjects.
• Easier device pairing: Supports NFC for fast wireless image transfer over short distances.
• More affordable: Was introduced into a lower priced category (63 percent cheaper at launch).
• More heavily discounted: Has been around for much longer (launched in February 2015).

If the count of relative strengths (bullet points above) is taken as a measure, the K-3 III is the clear winner of the match-up (20 : 8 points). However, the pertinence of the various camera strengths will differ across photographers, so that you might want to weigh individual camera traits according to their importance for your own imaging needs before making a camera decision. A professional wedding photographer will view the differences between cameras in a way that diverges from the perspective of a travel photog, and a person interested in cityscapes has distinct needs from a macro shooter. Hence, the decision which camera is best and worth buying is often a very personal one.

How about other alternatives? Do the specifications of the Pentax K-3 III and the Pentax K-S2 place the cameras among the top in their class? Find out in the latest Best DSLR Camera listing whether the two cameras rank among the cream of the crop.

In any case, while the specs-based evaluation of cameras can be instructive in revealing their potential as photographic tools, it remains partial and cannot reveal, for example, the shooting experience and imaging performance when actually working with the K-3 III or the K-S2. At times, user reviews, such as those published at amazon, address these issues in a useful manner, but such feedback is on many occasions incomplete, inconsistent, and unreliable.

Expert reviews

This is where reviews by experts come in. The adjacent summary-table relays the overall verdicts of several of the most popular camera review sites (amateurphotographer [AP], cameralabs [CL], digitalcameraworld [DCW], dpreview [DPR], ephotozine [EPZ], photographyblog [PB]). As can be seen, the professional reviewers agree in many cases on the quality of different cameras, but sometimes their assessments diverge, reinforcing the earlier point that a camera decision is often a very personal choice.

Expert Camera Reviews

		Camera   Model	AP   score	CL   score	DCW   score	DPR   score	EPZ   score	PB   score	Camera Launch	Launch Price (USD)	Street Price
1.		Pentax K-3 III	4/5	..	3/5	..	4.5/5	..	Mar 2021	1,999	amazon.com
2.		Pentax K-S2	4.5/5	..	..	..	5/5	4.5/5	Feb 2015	749	ebay.com
3.		Fujifilm X-H1	..	+	5/5	86/100	4.5/5	4.5/5	Feb 2018	1,899	ebay.com
4.		Nikon D780	5/5	..	5/5	87/100	4.5/5	4.5/5	Jan 2020	2,299	amazon.com
5.		Nikon Z6	5/5	..	5/5	89/100	4.5/5	5/5	Aug 2018	1,999	ebay.com
6.		Nikon Z6 II	4.5/5	..	4/5	89/100	4.5/5	4.5/5	Oct 2020	1,999	amazon.com
7.		Panasonic GH6	5/5	+ +	5/5	87/100	5/5	5/5	Feb 2022	2,199	amazon.com
8.		Panasonic S5	4.5/5	+ +	4.5/5	88/100	4.5/5	4.5/5	Sep 2020	1,999	amazon.com
9.		Pentax K-3	4/5	..	..	83/100	5/5	5/5	Oct 2013	1,299	ebay.com
10.		Pentax K-3 II	4.5/5	..	..	..	5/5	5/5	Apr 2015	1,099	ebay.com
11.		Pentax K-70	4.5/5	..	4/5	79/100	4.5/5	4.5/5	Jun 2016	649	ebay.com
12.		Pentax KP	4/5	..	3/5	82/100	5/5	4.5/5	Jan 2017	1,099	ebay.com
13.		Pentax K-S1	4/5	..	..	..	4.5/5	4/5	Aug 2014	749	ebay.com
Note: (+ +) highly recommended; (+) recommended; (o) reviewed; (..) not available.

The review scores listed above should be treated with care, though. The assessments were made in relation to similar cameras of the same technological generation. Hence, a score should always be seen in the context of the camera's market launch date and its price, and comparing ratings of very distinct cameras or ones that are far apart in terms of their release date have little meaning. Also, kindly note that some of the listed sites have over time developped their review approaches and their reporting style.

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Other camera comparisons

Did this review help to inform your camera decision process? If you would like to see a different side-by-side camera review, just use the search menu below. There is also a set of direct links to comparison reviews that other users of the CAM-parator app explored.

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