Olympus E-M1X vs Pentax K-S1

The Olympus OM-D E-M1X and the Pentax K-S1 are two digital cameras that were announced, respectively, in January 2019 and August 2014. The E-M1X is a mirrorless interchangeable lens camera, while the K-S1 is a DSLR. The cameras are based on a Four Thirds (E-M1X) and an APS-C (K-S1) 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-M1X		Pentax K-S1
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, 1037k dots		3.0 LCD, 921k dots
Swivel touchscreen		Fixed screen (not touch-sensitive)
18 shutter flaps per second		5.4 shutter flaps per second
In-body stabilization		In-body stabilization
Weathersealed body		not weather sealed
870 shots per battery charge		410 shots per battery charge
144 x 147 x 75 mm, 997 g		121 x 93 x 70 mm, 558 g

Going beyond this snapshot of core features and characteristics, what are the differences between the Olympus OM-D E-M1X and the Pentax K-S1? 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 Olympus E-M1X and the Pentax K-S1 are illustrated in the side-by-side display below. The two cameras are presented according to their relative size. Three consecutive views from the front, the top, and the rear side are shown. All size dimensions are rounded to the nearest millimeter.

The E-M1X can be obtained in two different colors (black, silver), while the K-S1 is available in four color-versions (black, grey, orange, white).

If the front view area (width x height) of the cameras is taken as an aggregate measure of their size, the Pentax K-S1 is considerably smaller (47 percent) than the Olympus E-M1X. Moreover, the K-S1 is substantially lighter (44 percent) than the E-M1X. It is worth mentioning in this context that the E-M1X is splash and dust resistant, while the K-S1 does not feature any corresponding weather-sealing.

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-M1X gets 870 shots out of its BLH-1 battery, while the K-S1 can take 410 images on a single charge of its D-LI109 power pack. As can be seen in the images above, the E-M1X has a battery grip built in. This facilitates image-taking in portrait orientation and gives it additional battery power. The power pack in the E-M1X can be charged via the USB port, so that it is not always necessary to take the battery charger along when travelling.

The following table provides a synthesis of the main physical specifications of the two cameras and other similar ones. 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-M1X	144 mm	147 mm	75 mm	997 g	870	Y	Jan 2019	2,999
2.		Pentax K-S1	121 mm	93 mm	70 mm	558 g	410	n	Aug 2014	749
3.		Canon R6	138 mm	98 mm	88 mm	680 g	360	Y	Jul 2020	2,499
4.		Nikon D5300	125 mm	98 mm	76 mm	480 g	600	n	Oct 2013	799
5.		Olympus E-M1 III	134 mm	91 mm	69 mm	580 g	420	Y	Feb 2020	1,799
6.		Olympus E-M10 IV	122 mm	84 mm	49 mm	383 g	360	n	Aug 2020	699
7.		Olympus E-M5 III	125 mm	85 mm	50 mm	414 g	310	Y	Oct 2019	1,199
8.		Olympus E-M1 II	134 mm	91 mm	67 mm	574 g	440	Y	Sep 2016	1,999
9.		Panasonic S1	149 mm	110 mm	97 mm	1017 g	400	Y	Feb 2019	2,499
10.		Panasonic S1R	149 mm	110 mm	97 mm	1016 g	380	Y	Feb 2019	3,699
11.		Panasonic G90	130 mm	94 mm	77 mm	536 g	290	Y	Apr 2019	999
12.		Panasonic S1H	151 mm	114 mm	110 mm	1052 g	400	Y	May 2019	3,999
13.		Pentax K-S2	123 mm	91 mm	73 mm	678 g	410	Y	Feb 2015	749
14.		Pentax K-500	130 mm	97 mm	71 mm	646 g	710	n	Jun 2013	549
15.		Pentax K-3	131 mm	100 mm	77 mm	800 g	560	Y	Oct 2013	1,299
16.		Sony A68	143 mm	104 mm	81 mm	610 g	540	n	Nov 2015	699
17.		Sony A900	156 mm	117 mm	82 mm	895 g	880	Y	Sep 2008	2,999
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-S1 was launched at a markedly lower price (by 75 percent) than the E-M1X, 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 imaging sensor is a crucial determinant 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. 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 more expensive and lead to bigger and heavier cameras and lenses.

Of the two cameras under consideration, the Olympus E-M1X features a Four Thirds sensor and the Pentax K-S1 an APS-C sensor. The sensor area in the K-S1 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-M1X has a native 4:3 aspect ratio, while the one in the K-S1 offers a 3:2 aspect.

In terms of underlying technology, both cameras are build around CMOS sensors.

Despite having a smaller sensor, the Olympus E-M1X offers a higher resolution of 20.2 megapixels, compared with 20 MP of the Pentax K-S1. 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-S1). However, it should be noted that the E-M1X is much more recent (by 4 years and 4 months) than the K-S1, 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-M1X has on-sensor phase detect pixels, which results in fast and reliable autofocus acquisition even during live view operation.

Unlike the K-S1, the E-M1X 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-M1X 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-S1 are ISO 100 to ISO 51200 (no boost).

For many cameras, data on sensor performance has been reported by DXO Mark. This service is based on lab testing and assigns an overall score to each camera sensor, as well as ratings for dynamic range ("DXO Landscape"), color depth ("DXO Portrait"), and low-light sensitivity ("DXO Sports"). 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-M1X	Four Thirds	20.2	5184	3888	4K/30p	..	..	..	..
2.		Pentax K-S1	APS-C	20.0	5472	3648	1080/30p	23.5	13.0	1061	78
3.		Canon R6	Full Frame	20.0	5472	3648	4k/60p	24.2	14.3	3394	90
4.		Nikon D5300	APS-C	24.0	6000	4000	1080/60p	24.0	13.9	1338	83
5.		Olympus E-M1 III	Four Thirds	20.2	5184	3888	4K/30p	..	..	..	..
6.		Olympus E-M10 IV	Four Thirds	20.2	5184	3888	4K/30p	..	..	..	..
7.		Olympus E-M5 III	Four Thirds	20.2	5184	3888	4K/30p	..	..	..	..
8.		Olympus E-M1 II	Four Thirds	20.2	5184	3888	4K/30p	23.7	12.8	1312	80
9.		Panasonic S1	Full Frame	24.0	6000	4000	4K/60p	25.2	14.5	3333	95
10.		Panasonic S1R	Full Frame	46.7	8368	5584	4K/60p	26.4	14.1	3525	100
11.		Panasonic G90	Four Thirds	20.2	5184	3888	4K/30p	..	..	..	..
12.		Panasonic S1H	Full Frame	24.0	6000	4000	6K/30p	..	..	..	..
13.		Pentax K-S2	APS-C	20.0	5472	3648	1080/30p	..	..	..	..
14.		Pentax K-500	APS-C	16.1	4928	3264	1080/30p	23.7	13.1	1087	79
15.		Pentax K-3	APS-C	24.1	6016	4000	1080/60i	23.7	13.4	1216	80
16.		Sony A68	APS-C	24.0	6000	4000	1080/60i	24.1	13.5	701	79
17.		Sony A900	Full Frame	24.4	6048	4032	none	23.7	12.3	1431	79

Many modern cameras are not only capable of taking still images, but can also record movies. The two cameras under consideration both have sensors whose read-out speed is fast enough to capture moving pictures, but the E-M1X provides a higher video resolution than the K-S1. It can shoot video footage at 4K/30p, while the Pentax is limited to 1080/30p.

Feature comparison

Beyond body and sensor, cameras can and do differ across a range of features. For example, the E-M1X has an electronic viewfinder (2360k dots), while the K-S1 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-M1X has a higher magnification than the one of the K-S1 (0.83x vs 0.63x), so that the size of the image transmitted appears closer to the size seen with the naked human eye. The adjacent table lists some of the other core features of the Olympus E-M1X and Pentax K-S1 along with similar information for a selection of comparators.

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-M1X	2360	n	3.0	1037	swivel	Y	1/8000s	18.0	n	Y
2.		Pentax K-S1	optical	n	3.0	921	fixed	n	1/6000s	5.4	Y	Y
3.		Canon R6	5760	n	3.0	1620	swivel	Y	1/8000s	12.0	n	Y
4.		Nikon D5300	optical	n	3.2	1037	swivel	n	1/4000s	5.0	Y	n
5.		Olympus E-M1 III	2360	n	3.0	1037	swivel	Y	1/8000s	18.0	n	Y
6.		Olympus E-M10 IV	2360	n	3.0	1040	tilting	Y	1/4000s	15.0	Y	Y
7.		Olympus E-M5 III	2360	n	3.0	1040	swivel	Y	1/8000s	10.0	n	Y
8.		Olympus E-M1 II	2360	n	3.0	1037	swivel	Y	1/8000s	18.0	n	Y
9.		Panasonic S1	5760	Y	3.2	2100	full-flex	Y	1/8000s	9.0	n	Y
10.		Panasonic S1R	5760	Y	3.2	2100	full-flex	Y	1/8000s	9.0	n	Y
11.		Panasonic G90	2360	n	3.0	1240	swivel	Y	1/4000s	9.0	Y	Y
12.		Panasonic S1H	5760	Y	3.2	2330	swivel	Y	1/8000s	9.0	n	Y
13.		Pentax K-S2	optical	n	3.0	921	swivel	n	1/6000s	5.4	Y	Y
14.		Pentax K-500	optical	n	3.0	921	fixed	n	1/6000s	6.0	Y	Y
15.		Pentax K-3	optical	Y	3.2	1037	fixed	n	1/8000s	8.3	Y	Y
16.		Sony A68	1440	Y	2.7	460	tilting	n	1/4000s	8.0	Y	Y
17.		Sony A900	optical	Y	3.0	922	fixed	n	1/8000s	5.0	n	Y

One differentiating feature between the two cameras concerns the touch sensitivity of the rear screen. The E-M1X has a touchscreen, while the K-S1 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-M1X 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-M1X has 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-M1X and the K-S1 write their files to SDXC cards. The E-M1X features dual card slots, which can be very useful in case a memory card fails. In contrast, the K-S1 only has one slot. The E-M1X supports UHS-II cards (on both slots), while the K-S1 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 Olympus OM-D E-M1X and Pentax K-S1 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-M1X	Y	stereo	mono	Y	Y	micro	3.0	Y	-	Y
2.		Pentax K-S1	Y	stereo	mono	-	-	micro	2.0	-	-	-
3.		Canon R6	Y	mono	mono	Y	Y	micro	3.2	Y	-	Y
4.		Nikon D5300	Y	stereo	mono	Y	-	mini	2.0	Y	-	-
5.		Olympus E-M1 III	Y	stereo	mono	Y	Y	micro	3.1	Y	-	Y
6.		Olympus E-M10 IV	Y	stereo	mono	-	-	micro	2.0	Y	-	Y
7.		Olympus E-M5 III	Y	stereo	mono	Y	-	micro	2.0	Y	-	Y
8.		Olympus E-M1 II	Y	stereo	mono	Y	Y	micro	3.0	Y	-	-
9.		Panasonic S1	Y	stereo	mono	Y	Y	full	3.1	Y	-	Y
10.		Panasonic S1R	Y	stereo	mono	Y	Y	full	3.1	Y	-	Y
11.		Panasonic G90	Y	stereo	mono	Y	Y	micro	2.0	Y	-	Y
12.		Panasonic S1H	Y	stereo	mono	Y	Y	full	3.1	Y	-	Y
13.		Pentax K-S2	Y	mono	mono	Y	-	micro	2.0	Y	Y	-
14.		Pentax K-500	Y	mono	mono	-	-	-	2.0	-	-	-
15.		Pentax K-3	Y	mono	mono	Y	Y	mini	3.0	-	-	-
16.		Sony A68	Y	stereo	mono	Y	-	micro	2.0	-	-	-
17.		Sony A900	Y	-	-	-	-	mini	2.0	-	-	-

It is notable that the E-M1X has a microphone port, which is missing on the K-S1. Such an external microphone input can help to substantially improve the quality of audio recordings when a good external microphone is used.

Studio photographers will appreciate that the Olympus E-M1X (unlike the K-S1) 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 E-M1X has an internal geolocalization sensor and can record GPS coordinates in its EXIF data.

The E-M1X is a recent model that features in the current product line-up of Olympus. In contrast, the K-S1 has been discontinued (but can be found pre-owned on eBay). As a replacement in the same line of cameras, the K-S1 was succeeded by the Pentax K-S2. 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 what conclusions can be drawn? Is the Olympus E-M1X better than the Pentax K-S1 or vice versa? The listing below highlights the relative strengths of the two models.

Arguments in favor of the Olympus OM-D E-M1X:

• 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.
• Better sound: Can connect to an external microphone for higher quality sound recording.
• Better sound control: Has a headphone port that enables audio monitoring while recording.
• More framing info: Has an electronic viewfinder that displays shooting data.
• Larger viewfinder image: Features a viewfinder with a higher magnification (0.83x vs 0.63x).
• More detailed LCD: Has a higher resolution rear screen (1037k vs 921k dots).
• More flexible LCD: Has a swivel screen for odd-angle shots in portrait or landscape orientation.
• Fewer buttons to press: Is equipped with a touch-sensitive rear screen to facilitate handling.
• More selfie-friendly: Has an articulated screen that can be turned to be front-facing.
• Faster shutter: Has higher mechanical shutter speed (1/8000s vs 1/6000s) to freeze action.
• Faster burst: Shoots at higher frequency (18 vs 5.4 flaps/sec) to capture the decisive moment.
• Less disturbing: Has an electronic shutter option for completely silent shooting.
• Easier time-lapse photography: Has an intervalometer built-in for low frequency shooting.
• More portrait friendly: Features an integrated vertical grip for easier portrait shooting.
• Longer lasting: Can take more shots (870 versus 410) on a single battery charge.
• Easier travel charging: Can be conveniently charged via its USB port.
• Better sealing: Is weather sealed to enable shooting in dusty or wet environments.
• More legacy lens friendly: Can take a broad range of non-native lenses via adapters.
• Easier geotagging: Features an internal GPS sensor to log localization data.
• Faster data transfer: Supports a more advanced USB protocol (3.0 vs 2.0).
• Easier file upload: Has wifi built in for automatic backup or image transfer to the web.
• 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 4 years and 4 months of technical progress since the K-S1 launch.

Advantages of the Pentax K-S1:

• Brighter framing: Features an optical viewfinder for clear, lag-free composition.
• More compact: Is smaller (121x93mm vs 144x147mm) and will fit more readily into a bag.
• Less heavy: Has a lower weight (by 439g or 44 percent) and is thus easier to take along.
• Easier fill-in: Has a small integrated flash to brighten shadows of backlit subjects.
• More affordable: Was introduced into a lower priced category (75 percent cheaper at launch).
• More heavily discounted: Has been around for much longer (launched in August 2014).

If the count of relative strengths (bullet points above) is taken as a measure, the E-M1X is the clear winner of the match-up (28 : 6 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 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-M1X and the Pentax K-S1 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 technical specifications can provide a useful overview of the capabilities of different cameras, it remains partial and cannot reveal, for example, the shooting experience and imaging performance when actually working with the E-M1X or the K-S1. 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 why expert reviews are important. The table below provides a synthesis of the camera assessments of some of the best known photo-gear 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-M1X	4.5/5	o	..	4.5/5	..	Jan 2019	2,999
2.		Pentax K-S1	4/5	..	..	4.5/5	4/5	Aug 2014	749
3.		Canon R6	5/5	+ +	90/100	4.5/5	5/5	Jul 2020	2,499
4.		Nikon D5300	4/5	+ +	79/100	4.5/5	4.5/5	Oct 2013	799
5.		Olympus E-M1 III	5/5	..	83/100	4.5/5	4/5	Feb 2020	1,799
6.		Olympus E-M10 IV	4.5/5	..	..	4.5/5	4.5/5	Aug 2020	699
7.		Olympus E-M5 III	5/5	+	82/100	4.5/5	4.5/5	Oct 2019	1,199
8.		Olympus E-M1 II	5/5	+ +	85/100	4.5/5	4.5/5	Sep 2016	1,999
9.		Panasonic S1	4.5/5	+ +	88/100	4.5/5	4/5	Feb 2019	2,499
10.		Panasonic S1R	4.5/5	..	89/100	4.5/5	4.5/5	Feb 2019	3,699
11.		Panasonic G90	4.5/5	+	83/100	4.5/5	4.5/5	Apr 2019	999
12.		Panasonic S1H	..	..	90/100	..	..	May 2019	3,999
13.		Pentax K-S2	4.5/5	..	..	5/5	4.5/5	Feb 2015	749
14.		Pentax K-500	..	..	..	4.5/5	4.5/5	Jun 2013	549
15.		Pentax K-3	4/5	..	83/100	5/5	5/5	Oct 2013	1,299
16.		Sony A68	3/5	..	..	4/5	4/5	Nov 2015	699
17.		Sony A900	..	+ +	+ +	4.5/5	5/5	Sep 2008	2,999
Notes: (+ +) highly recommended; (+) recommended; (o) reviewed; (..) not available.

The above review scores should be interpreted with care, though. The ratings were established in reference to similarly priced cameras that were available in the market at the time of the review. Thus, a score needs to be put into the context of the launch date and the launch price of the camera, and comparing ratings of very distinct cameras or ones that are far apart in terms of their release date have little meaning. It should also be noted that some of the review sites have over time altered the way they render their verdicts.

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 a corresponding selection in the search boxes 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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Specifications: Olympus E-M1X vs Pentax K-S1

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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