Olympus E-M5 III vs Pentax K-S2

The Olympus OM-D E-M5 Mark III and the Pentax K-S2 are two digital cameras that were announced, respectively, in October 2019 and February 2015. The E-M5 III is a mirrorless interchangeable lens camera, while the K-S2 is a DSLR. The cameras are based on a Four Thirds (E-M5 III) and an APS-C (K-S2) sensor. The Olympus has a resolution of 20.2 megapixels, whereas the Pentax provides 20 MP.

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

Headline Specifications

Olympus E-M5 III		Pentax K-S2
Mirrorless system camera		Digital single lens reflex
Micro Four Thirds lenses		Pentax K mount lenses
20.2 MP, Four Thirds Sensor		20 MP, APS-C Sensor
4K/30p Video		1080/30p Video
ISO 200-25,600		ISO 100-51,200
Electronic viewfinder (2360k dots)		Optical viewfinder
3.0 LCD, 1040k dots		3.0 LCD, 921k dots
Swivel touchscreen		Swivel screen (not touch-sensitive)
10 shutter flaps per second		5.4 shutter flaps per second
In-body stabilization		In-body stabilization
Weathersealed body		Weathersealed body
310 shots per battery charge		410 shots per battery charge
125 x 85 x 50 mm, 414 g		123 x 91 x 73 mm, 678 g

Going beyond this snapshot of core features and characteristics, what are the differences between the Olympus OM-D E-M5 Mark 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 side-by-side display below illustrates the physical size and weight of the Olympus E-M5 III and the Pentax K-S2. The two cameras are presented according to their relative size. Three successive views from the front, the top, and the rear are shown. All width, height and depth dimensions are rounded to the nearest millimeter.

The E-M5 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 larger (5 percent) than the Olympus E-M5 III. Moreover, the K-S2 is substantially heavier (64 percent) than the E-M5 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 E-M5 III gets 310 shots out of its BLS-50 battery, while the K-S2 can take 410 images on a single charge of its D-LI109 power pack. The power pack in the E-M5 III can be charged via the USB port, so that it is not always necessary to take the battery charger along when travelling.

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.		Olympus E-M5 III	125 mm	85 mm	50 mm	414 g	310	Y	Oct 2019	1,199
2.		Pentax K-S2	123 mm	91 mm	73 mm	678 g	410	Y	Feb 2015	749
3.		Olympus E-M1 III	134 mm	91 mm	69 mm	580 g	420	Y	Feb 2020	1,799
4.		Olympus E-M10 IV	122 mm	84 mm	49 mm	383 g	360	n	Aug 2020	699
5.		Olympus E-M1X	144 mm	147 mm	75 mm	997 g	870	Y	Jan 2019	2,999
6.		Olympus PEN-F	125 mm	72 mm	37 mm	427 g	330	n	Jan 2016	1,199
7.		Olympus E-M5 II	124 mm	85 mm	45 mm	469 g	310	Y	Feb 2015	1,099
8.		Olympus E-M1	130 mm	94 mm	63 mm	497 g	350	Y	Sep 2013	1,399
9.		Olympus E-M5	122 mm	89 mm	43 mm	425 g	360	Y	Feb 2012	1,299
10.		Panasonic G90	130 mm	94 mm	77 mm	536 g	290	Y	Apr 2019	999
11.		Panasonic GX8	133 mm	78 mm	63 mm	487 g	330	Y	Jul 2015	1,199
12.		Pentax KP	132 mm	101 mm	76 mm	703 g	390	Y	Jan 2017	1,099
13.		Pentax K-70	126 mm	93 mm	74 mm	688 g	410	Y	Jun 2016	649
14.		Pentax K-3 II	131 mm	100 mm	77 mm	800 g	720	Y	Apr 2015	1,099
15.		Pentax K-S1	121 mm	93 mm	70 mm	558 g	410	n	Aug 2014	749
16.		Pentax K-3	131 mm	100 mm	77 mm	800 g	560	Y	Oct 2013	1,299
17.		Sony A6600	120 mm	67 mm	69 mm	503 g	810	Y	Aug 2019	1,399
Notes: 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 obviously take relative prices into account. The retail prices at the time of the camera’s release place the model in the market relative to other models in the producer’s line-up and the competition. The K-S2 was launched at a markedly lower price (by 38 percent) than the E-M5 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 imaging sensor is at the core of digital cameras and its size is one of the main determining factors of image quality. All other things equal, a large sensor will have larger individual pixel-units that offer better low-light sensitivity, wider dynamic range, and richer color-depth than smaller pixels in a sensor of the same technological generation. Further, a large sensor camera will give the photographer additional creative options when using shallow depth-of-field to isolate a subject from its background. On the downside, larger sensors tend to be associated with larger, more expensive camera bodies and lenses.

Of the two cameras under consideration, the Olympus E-M5 III features a Four Thirds sensor and the Pentax K-S2 an APS-C sensor. The sensor area in the K-S2 is 63 percent bigger. As a result of these sensor size differences, the cameras have a format factor of, respectively, 2.0 and 1.5. The sensor in the E-M5 III has a native 4:3 aspect ratio, while the one in the K-S2 offers a 3:2 aspect.

Despite having a smaller sensor, the Olympus E-M5 III offers a higher resolution of 20.2 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 3.34μm versus 4.28μm for the K-S2). However, it should be noted that the E-M5 III is much more recent (by 4 years and 8 months) 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 E-M5 III has on-sensor phase detect pixels, which results in fast and reliable autofocus acquisition even during live view operation.

Unlike the K-S2, the E-M5 III has the capacity to capture high quality composite images (80MP) 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 Olympus OM-D E-M5 Mark III has a native sensitivity range from ISO 200 to ISO 25600, which can be extended to ISO 64-25600. The corresponding ISO settings for the Pentax K-S2 are ISO 100 to ISO 51200 (no boost).

Since 2007, DXO Mark has published sensor performance measurements that have been derived using a consistent methodology. This service determines an overall sensor rating, as well as sub-scores for low-light sensitivity ("DXO Sports"), dynamic range ("DXO Landscape"), and color depth ("DXO Portrait"). The adjacent table reports on the physical sensor characteristics and the outcomes of the DXO sensor quality tests for a sample of comparator-cameras.

Sensor Characteristics

		Camera Model	Sensor Class	Resolution (MP)	Horiz. Pixels	Vert. Pixels	Video Format	DXO Portrait	DXO Landscape	DXO Sports	DXO Overall
1.		Olympus E-M5 III	Four Thirds	20.2	5184	3888	4K/30p	..	..	..	..
2.		Pentax K-S2	APS-C	20.0	5472	3648	1080/30p	..	..	..	..
3.		Olympus E-M1 III	Four Thirds	20.2	5184	3888	4K/30p	..	..	..	..
4.		Olympus E-M10 IV	Four Thirds	20.2	5184	3888	4K/30p	..	..	..	..
5.		Olympus E-M1X	Four Thirds	20.2	5184	3888	4K/30p	..	..	..	..
6.		Olympus PEN-F	Four Thirds	20.2	5184	3888	1080/60p	23.1	12.4	894	74
7.		Olympus E-M5 II	Four Thirds	15.9	4608	3456	1080/60p	23.0	12.5	842	73
8.		Olympus E-M1	Four Thirds	15.9	4608	3456	1080/30p	23.0	12.7	757	73
9.		Olympus E-M5	Four Thirds	15.9	4608	3456	1080/60i	22.8	12.3	826	71
10.		Panasonic G90	Four Thirds	20.2	5184	3888	4K/30p	..	..	..	..
11.		Panasonic GX8	Four Thirds	20.2	5184	3888	4K/30p	23.5	12.6	806	75
12.		Pentax KP	APS-C	24.1	6016	4000	1080/60i	..	..	..	..
13.		Pentax K-70	APS-C	24.0	6000	4000	1080/60i	..	..	..	..
14.		Pentax K-3 II	APS-C	24.1	6016	4000	1080/60i	23.6	13.6	1106	80
15.		Pentax K-S1	APS-C	20.0	5472	3648	1080/30p	23.5	13.0	1061	78
16.		Pentax K-3	APS-C	24.1	6016	4000	1080/60i	23.7	13.4	1216	80
17.		Sony A6600	APS-C	24.0	6000	4000	4K/30p	23.8	13.4	1497	82

Many modern cameras are not only capable of taking still images, but can also record movies. Both cameras under consideration have a sensor with sufficiently fast read-out times for moving pictures, but the E-M5 III provides a higher video resolution than the K-S2. It can shoot video footage at 4K/30p, while the Pentax is limited to 1080/30p.

Feature comparison

Apart from body and sensor, cameras can and do differ across a range of features. For example, the E-M5 III has an electronic viewfinder (2360k dots), while the K-S2 has an optical one. Both systems have their advantages, with the electronic viewfinder making it possible to project supplementary shooting information into the framing view, whereas the optical viewfinder offers lag-free viewing and a very clear framing image. The viewfinders of both cameras offer the same field of view (100%), but the viewfinder of the E-M5 III has a higher magnification than the one of the K-S2 (0.68x vs 0.63x), so that the size of the image transmitted appears closer to the size seen with the naked human eye. The following table reports on some other key feature differences and similarities of the Olympus E-M5 III, the Pentax K-S2, and comparable cameras.

Core Features

		Camera Model	Viewfinder (Type or 000 dots)	Control Panel (yes/no)	LCD Size (inch)	LCD Resolution (000 dots)	LCD Attach- ment	Touch Screen (yes/no)	Mech Shutter Speed	Shutter Flaps (1/sec)	Built-in Flash (yes/no)	Built-in Image Stab
1.		Olympus E-M5 III	2360	n	3.0	1040	swivel	Y	1/8000s	10.0	n	Y
2.		Pentax K-S2	optical	n	3.0	921	swivel	n	1/6000s	5.4	Y	Y
3.		Olympus E-M1 III	2360	n	3.0	1037	swivel	Y	1/8000s	18.0	n	Y
4.		Olympus E-M10 IV	2360	n	3.0	1040	tilting	Y	1/4000s	15.0	Y	Y
5.		Olympus E-M1X	2360	n	3.0	1037	swivel	Y	1/8000s	18.0	n	Y
6.		Olympus PEN-F	2360	n	3.0	1037	swivel	Y	1/8000s	10.0	n	Y
7.		Olympus E-M5 II	2360	n	3.0	1037	swivel	Y	1/8000s	10.0	n	Y
8.		Olympus E-M1	2360	n	3.0	1037	tilting	Y	1/8000s	10.0	n	Y
9.		Olympus E-M5	1440	n	3.0	610	tilting	Y	1/4000s	9.0	n	Y
10.		Panasonic G90	2360	n	3.0	1240	swivel	Y	1/4000s	9.0	Y	Y
11.		Panasonic GX8	2360	n	3.0	1040	swivel	Y	1/8000s	10.0	n	Y
12.		Pentax KP	optical	n	3.0	921	tilting	n	1/6000s	7.0	Y	Y
13.		Pentax K-70	optical	n	3.0	921	swivel	n	1/6000s	6.0	Y	Y
14.		Pentax K-3 II	optical	Y	3.2	1037	fixed	n	1/8000s	8.3	n	Y
15.		Pentax K-S1	optical	n	3.0	921	fixed	n	1/6000s	5.4	Y	Y
16.		Pentax K-3	optical	Y	3.2	1037	fixed	n	1/8000s	8.3	Y	Y
17.		Sony A6600	2359	n	3.0	922	tilting	Y	1/4000s	11.0	n	Y

One differentiating feature between the two cameras concerns the touch sensitivity of the rear screen. The E-M5 III has a touchscreen, while the K-S2 has a conventional panel. Touch control can be particularly helpful, for example, for setting the focus point.

The reported shutter speed information refers to the use of the mechanical shutter. Yet, some cameras only have an electronic shutter, while others have an electronic shutter in addition to a mechanical one. In fact, the E-M5 III is one of those camera that have an additional electronic shutter, which makes completely silent shooting possible. However, this mode is less suitable for photographing moving objects (risk of rolling shutter) or shooting under artificial light sources (risk of flickering).

The Olympus E-M5 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 E-M5 III and the K-S2 write their files to SDXC cards. The E-M5 III supports UHS-II cards (Ultra High Speed data transfer of up to 312 MB/s), while the K-S2 can use UHS-I cards (up to 104 MB/s).

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 Olympus OM-D E-M5 Mark 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 Microphone	Internal Speaker	Microphone Port	Headphone Port	HDMI Port	USB Port	WiFi Support	NFC Support	Bluetooth Support
1.		Olympus E-M5 III	Y	stereo	mono	Y	-	micro	2.0	Y	-	Y
2.		Pentax K-S2	Y	mono	mono	Y	-	micro	2.0	Y	Y	-
3.		Olympus E-M1 III	Y	stereo	mono	Y	Y	micro	3.1	Y	-	Y
4.		Olympus E-M10 IV	Y	stereo	mono	-	-	micro	2.0	Y	-	Y
5.		Olympus E-M1X	Y	stereo	mono	Y	Y	micro	3.0	Y	-	Y
6.		Olympus PEN-F	Y	stereo	mono	-	-	micro	2.0	Y	-	-
7.		Olympus E-M5 II	Y	stereo	mono	Y	-	micro	2.0	Y	-	-
8.		Olympus E-M1	Y	stereo	mono	Y	-	micro	2.0	Y	-	-
9.		Olympus E-M5	Y	stereo	mono	-	-	mini	2.0	-	-	-
10.		Panasonic G90	Y	stereo	mono	Y	Y	micro	2.0	Y	-	Y
11.		Panasonic GX8	Y	stereo	mono	Y	-	micro	2.0	Y	Y	-
12.		Pentax KP	Y	stereo	mono	Y	-	-	2.0	Y	-	-
13.		Pentax K-70	Y	stereo	mono	Y	-	mini	2.0	Y	-	-
14.		Pentax K-3 II	Y	mono	mono	Y	Y	mini	3.0	-	-	-
15.		Pentax K-S1	Y	stereo	mono	-	-	micro	2.0	-	-	-
16.		Pentax K-3	Y	mono	mono	Y	Y	mini	3.0	-	-	-
17.		Sony A6600	Y	stereo	mono	Y	Y	YES	2.0	Y	Y	Y

Both the E-M5 III and the K-S2 are recent models that are part of the current product line-up. The K-S2 replaced the earlier Pentax K-S1, while the E-M5 III followed on from the Olympus E-M5 II. Further information on the two cameras (e.g. user guides, manuals), as well as related accessories, can be found on the official Olympus and Pentax websites.

Review summary

So how do things add up? Is the Olympus E-M5 III better than the Pentax K-S2 or vice versa? The listing below highlights the relative strengths of the two models.

Arguments in favor of the Olympus OM-D E-M5 Mark III:

• High quality composites: Can combine several shots after pixel-shifting its sensor.
• Better video: Provides higher definition movie capture (4K/30p vs 1080/30p).
• Better live-view autofocus: Features on-sensor phase-detection for more confident autofocus.
• More framing info: Has an electronic viewfinder that displays shooting data.
• Larger viewfinder image: Features a viewfinder with a higher magnification (0.68x vs 0.63x).
• More detailed LCD: Has a higher resolution rear screen (1040k 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 (10 vs 5.4 flaps/sec) to capture the decisive moment.
• Less disturbing: Has an electronic shutter option for completely silent shooting.
• Less heavy: Is lighter (by 264g or 39 percent) and hence easier to carry around.
• Easier travel charging: Can be conveniently charged via its USB port.
• More legacy lens friendly: Can take a broad range of non-native lenses via adapters.
• Easier wireless transfer: Supports Bluetooth for image sharing without cables.
• Faster buffer clearing: Supports a more advanced SD data transfer standard (UHS-II vs UHS-I).
• More modern: Reflects 4 years and 8 months of technical progress since the K-S2 launch.

Reasons to prefer the Pentax K-S2:

• Brighter framing: Features an optical viewfinder for clear, lag-free composition.
• Longer lasting: Gets more shots (410 versus 310) out of a single battery charge.
• 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 (38 percent cheaper at launch).
• More heavily discounted: Has been around for much longer (launched in February 2015).

If the count of individual advantages (bullet points above) is taken as a guide, the E-M5 III is the clear winner of the match-up (16 : 6 points). However, the relative importance of the various individual camera aspects will vary according to personal preferences and needs, so that you might like to apply corresponding weights to the particular features before making a decision on a new camera. A professional wildlife photographer will view the differences between cameras in a way that diverges from the perspective of a family photog, and a person interested in architecture has distinct needs from a sports 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 Olympus E-M5 III and the Pentax K-S2 place the cameras among the top in their class? Find out in the latest Best Mirrorless Interchangeable Lens Camera and Best DSLR Camera listings whether the two cameras rank among the cream of the crop.

In any case, while the comparison of the spec-sheets of cameras can offer a general idea of their imaging potential, it says little about, for example, the shooting experience and imaging performance of the E-M5 III and the K-S2 in practical situations. User reviews that are available, for instance, at amazon can sometimes shed light on these issues, but such feedback is all too often partial, inconsistent, and inaccurate.

Expert reviews

This is why expert reviews are important. The following table reports the overall ratings of the cameras as published by some of the major camera review sites (amateurphotographer [AP], cameralabs [CL], 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	DPR   score	EPZ   score	PB   score	Camera Launch	Launch Price (USD)	Street Price
1.		Olympus E-M5 III	5/5	+	82/100	4.5/5	4.5/5	Oct 2019	1,199
2.		Pentax K-S2	4.5/5	..	..	5/5	4.5/5	Feb 2015	749
3.		Olympus E-M1 III	5/5	..	83/100	4.5/5	4/5	Feb 2020	1,799
4.		Olympus E-M10 IV	4.5/5	..	..	4.5/5	4.5/5	Aug 2020	699
5.		Olympus E-M1X	4.5/5	o	..	4.5/5	..	Jan 2019	2,999
6.		Olympus PEN-F	..	..	82/100	4.5/5	5/5	Jan 2016	1,199
7.		Olympus E-M5 II	5/5	+ +	81/100	5/5	5/5	Feb 2015	1,099
8.		Olympus E-M1	5/5	+ +	84/100	4.5/5	4.5/5	Sep 2013	1,399
9.		Olympus E-M5	4/5	+ +	80/100	4.5/5	5/5	Feb 2012	1,299
10.		Panasonic G90	4.5/5	+	83/100	4.5/5	4.5/5	Apr 2019	999
11.		Panasonic GX8	5/5	+	82/100	4.5/5	4.5/5	Jul 2015	1,199
12.		Pentax KP	4/5	..	82/100	5/5	4.5/5	Jan 2017	1,099
13.		Pentax K-70	4.5/5	..	79/100	4.5/5	4.5/5	Jun 2016	649
14.		Pentax K-3 II	4.5/5	..	..	5/5	5/5	Apr 2015	1,099
15.		Pentax K-S1	4/5	..	..	4.5/5	4/5	Aug 2014	749
16.		Pentax K-3	4/5	..	83/100	5/5	5/5	Oct 2013	1,299
17.		Sony A6600	4/5	+	83/100	4.5/5	4/5	Aug 2019	1,399
Notes: (+ +) highly recommended; (+) recommended; (o) reviewed; (..) not available.

The above review scores should be interpreted with care, though. The ratings are only valid when referring to cameras in the same category and of the same age. A score, therefore, has to be seen in close connection to the price and market introduction time of the camera, and rating-comparisons among cameras that span long time periods or concern very differently equipped models make little sense. Also, please note that some of the review sites have changed their methodology and reporting over time.

Other camera comparisons

Did this review help to inform your camera decision process? In case you are interested in seeing how other cameras pair up, just make your choice using the following search menu. As an alternative, you can also directly jump to any one of the listed comparisons that were previously generated by the CAM-parator tool.

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Specifications: Olympus E-M5 III vs Pentax K-S2

Below is a side-by-side comparison of the specs of the two cameras to facilitate a quick review of their differences and common features.

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