Olympus E-M10 IV vs Pentax K-S1

The Olympus OM-D E-M10 Mark IV and the Pentax K-S1 are two digital cameras that were announced, respectively, in August 2020 and August 2014. The E-M10 IV is a mirrorless interchangeable lens camera, while the K-S1 is a DSLR. The cameras are based on a Four Thirds (E-M10 IV) 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-M10 IV		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 – 1040k dots		3.0" LCD – 921k dots
Tilting touchscreen		Fixed screen (not touch-sensitive)
15 shutter flaps per second		5.4 shutter flaps per second
In-body stabilization		In-body stabilization
360 shots per battery charge		410 shots per battery charge
122 x 84 x 49 mm, 383 g		121 x 93 x 70 mm, 558 g

Check E-M10 IV price at
amazon.com
Check K-S1 offers at
ebay.com

Going beyond this snapshot of core features and characteristics, what are the differences between the Olympus OM-D E-M10 Mark IV 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

An illustration of the physical size and weight of the Olympus E-M10 IV and the Pentax K-S1 is provided in the side-by-side display below. The two cameras are presented according to their relative size. Three consecutive perspectives from the front, the top, and the back are available. All size dimensions are rounded to the nearest millimeter.

The E-M10 IV 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 notably larger (10 percent) than the Olympus E-M10 IV. Moreover, the K-S1 is substantially heavier (46 percent) than the E-M10 IV. In this context, it is worth noting that neither the E-M10 IV nor the K-S1 are weather-sealed.

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-M10 IV gets 360 shots out of its Olympus BLS-50 battery, while the K-S1 can take 410 images on a single charge of its Pentax D-LI109 power pack. The power pack in the E-M10 IV 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. In case you want to display and compare another camera duo, you can use the CAM-parator app to select your camera combination among a large number of options.

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-M10 IV	122 mm	84 mm	49 mm	383 g	360	n	Aug 2020	699	amazon.com
2.		Pentax K-S1	121 mm	93 mm	70 mm	558 g	410	n	Aug 2014	749	ebay.com
3.		Nikon D5300	125 mm	98 mm	76 mm	480 g	600	n	Oct 2013	799	ebay.com
4.		Nikon D5500	124 mm	97 mm	70 mm	470 g	820	n	Jan 2015	899	ebay.com
5.		Olympus E-M5 III	125 mm	85 mm	50 mm	414 g	310	Y	Oct 2019	1,199	ebay.com
6.		Olympus E-M10	119 mm	82 mm	46 mm	396 g	320	n	Jan 2014	699	ebay.com
7.		Olympus E-M10 II	120 mm	83 mm	47 mm	390 g	320	n	Aug 2015	649	ebay.com
8.		Olympus E-M10 III	122 mm	84 mm	50 mm	410 g	330	n	Aug 2017	649	ebay.com
9.		Olympus E-P7	118 mm	69 mm	38 mm	337 g	360	n	Jun 2021	799	amazon.com
10.		Olympus E-PL7	115 mm	67 mm	38 mm	357 g	350	n	Aug 2014	599	ebay.com
11.		Olympus E-PL8	115 mm	67 mm	38 mm	357 g	350	n	Sep 2016	549	ebay.com
12.		Olympus E-PL9	117 mm	68 mm	39 mm	380 g	350	n	Feb 2018	599	ebay.com
13.		Olympus E-PL10	117 mm	68 mm	39 mm	380 g	350	n	Oct 2019	599	ebay.com
14.		Olympus PEN-F	125 mm	72 mm	37 mm	427 g	330	n	Jan 2016	1,199	ebay.com
15.		Pentax K-500	130 mm	97 mm	71 mm	646 g	710	n	Jun 2013	549	ebay.com
16.		Pentax K-S2	123 mm	91 mm	73 mm	678 g	410	Y	Feb 2015	749	ebay.com
17.		Sony A68	143 mm	104 mm	81 mm	610 g	540	n	Nov 2015	699	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 obviously take relative prices into account. The listed launch prices provide an indication of the market segment that the manufacturer of the cameras have been targeting. The E-M10 IV was somewhat cheaper (by 7 percent) than the K-S1 at launch, but both cameras fall into the same price category. 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. Then, after the new model is out, very good deals can frequently be found on the pre-owned market.

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. 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. Furthermore, a large sensor camera will give the photographer more possibilities to use shallow depth-of-field in order to 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.

Of the two cameras under consideration, the Olympus E-M10 IV 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-M10 IV has a native 4:3 aspect ratio, while the one in the K-S1 offers a 3:2 aspect.

Despite having a smaller sensor, the Olympus E-M10 IV 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-M10 IV is much more recent (by 5 years and 11 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 Olympus OM-D E-M10 Mark IV has a native sensitivity range from ISO 200 to ISO 25600, which can be extended to ISO 100-25600. The corresponding ISO settings for the Pentax K-S1 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 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 table below summarizes the physical sensor characteristics and sensor quality findings and compares them across a set of similar 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-M10 IV	Four Thirds	20.2	5184	3888	4K/30p	23.3	13.2	1402	76
2.		Pentax K-S1	APS-C	20.0	5472	3648	1080/30p	23.5	13.0	1061	78
3.		Nikon D5300	APS-C	24.0	6000	4000	1080/60p	24.0	13.9	1338	83
4.		Nikon D5500	APS-C	24.0	6000	4000	1080/60p	24.1	14.0	1438	84
5.		Olympus E-M5 III	Four Thirds	20.2	5184	3888	4K/30p	23.3	13.1	1324	76
6.		Olympus E-M10	Four Thirds	15.9	4608	3456	1080/30p	22.8	12.3	884	72
7.		Olympus E-M10 II	Four Thirds	15.9	4608	3456	1080/60p	23.1	12.5	842	73
8.		Olympus E-M10 III	Four Thirds	15.9	4608	3456	4K/30p	23.1	12.8	1120	74
9.		Olympus E-P7	Four Thirds	20.2	5184	3888	4K/30p	23.4	13.3	1494	77
10.		Olympus E-PL7	Four Thirds	15.9	4608	3456	1080/30p	22.7	12.4	873	72
11.		Olympus E-PL8	Four Thirds	15.9	4608	3456	1080/30p	23.0	12.6	1030	73
12.		Olympus E-PL9	Four Thirds	15.9	4608	3456	4K/30p	23.1	12.8	1162	74
13.		Olympus E-PL10	Four Thirds	15.9	4608	3456	4K/30p	23.3	13.1	1324	76
14.		Olympus PEN-F	Four Thirds	20.2	5184	3888	1080/60p	23.1	12.4	894	74
15.		Pentax K-500	APS-C	16.1	4928	3264	1080/30p	23.7	13.1	1087	79
16.		Pentax K-S2	APS-C	20.0	5472	3648	1080/30p	23.6	12.9	1514	79
17.		Sony A68	APS-C	24.0	6000	4000	1080/60i	24.1	13.5	701	79
Note: DXO values in italics represent estimates based on sensor size and age.

Many modern cameras cannot only take still pictures, but also record videos. Both cameras under consideration have a sensor with sufficiently fast read-out times for moving pictures, but the E-M10 IV 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

Apart from body and sensor, cameras can and do differ across a range of features. For example, the E-M10 IV 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 K-S1 has a higher magnification than the one of the E-M10 IV (0.63x vs 0.62x), 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-M10 IV 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 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.		Olympus E-M10 IV	2360	n	3.0 / 1040	tilting	Y	1/4000s	15.0/s	Y	Y
2.		Pentax K-S1	optical	n	3.0 / 921	fixed	n	1/6000s	5.4/s	Y	Y
3.		Nikon D5300	optical	n	3.2 / 1037	swivel	n	1/4000s	5.0/s	Y	n
4.		Nikon D5500	optical	n	3.2 / 1037	swivel	Y	1/4000s	5.0/s	Y	n
5.		Olympus E-M5 III	2360	n	3.0 / 1040	swivel	Y	1/8000s	10.0/s	n	Y
6.		Olympus E-M10	1440	n	3.0 / 1037	tilting	Y	1/4000s	8.0/s	Y	Y
7.		Olympus E-M10 II	2360	n	3.0 / 1040	tilting	Y	1/4000s	8.0/s	Y	Y
8.		Olympus E-M10 III	2360	n	3.0 / 1040	tilting	Y	1/4000s	8.6/s	Y	Y
9.		Olympus E-P7	none	n	3.0 / 1040	tilting	Y	1/4000s	8.7/s	Y	Y
10.		Olympus E-PL7	optional	n	3.0 / 1037	tilting	Y	1/4000s	8.0/s	n	Y
11.		Olympus E-PL8	optional	n	3.0 / 1037	tilting	Y	1/4000s	8.0/s	n	Y
12.		Olympus E-PL9	none	n	3.0 / 1040	tilting	Y	1/4000s	8.6/s	Y	Y
13.		Olympus E-PL10	none	n	3.0 / 1040	tilting	Y	1/4000s	8.6/s	Y	Y
14.		Olympus PEN-F	2360	n	3.0 / 1037	swivel	Y	1/8000s	10.0/s	n	Y
15.		Pentax K-500	optical	n	3.0 / 921	fixed	n	1/6000s	6.0/s	Y	Y
16.		Pentax K-S2	optical	n	3.0 / 921	swivel	n	1/6000s	5.4/s	Y	Y
17.		Sony A68	1440	Y	2.7 / 460	tilting	n	1/4000s	8.0/s	Y	Y
Note: *) Information refers to the mechanical shutter, unless the camera only has an electronic one.

One differentiating feature between the two cameras concerns the touch sensitivity of the rear screen. The E-M10 IV 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-M10 IV 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-M10 IV 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-M10 IV and the K-S1 write their files to SDXC cards. The E-M10 IV supports UHS-II cards (Ultra High Speed data transfer of up to 312 MB/s), while the K-S1 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-M10 Mark IV 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 Mic / Speaker	Microphone Port	Headphone Port	HDMI Port	USB Port	WiFi Support	NFC Support	Bluetooth Support
1.		Olympus E-M10 IV	Y	stereo / mono	-	-	micro	2.0	Y	-	Y
2.		Pentax K-S1	Y	stereo / mono	-	-	micro	2.0	-	-	-
3.		Nikon D5300	Y	stereo / mono	Y	-	mini	2.0	Y	-	-
4.		Nikon D5500	Y	stereo / mono	Y	-	mini	2.0	Y	-	-
5.		Olympus E-M5 III	Y	stereo / mono	Y	-	micro	2.0	Y	-	Y
6.		Olympus E-M10	Y	stereo / mono	-	-	micro	2.0	Y	-	-
7.		Olympus E-M10 II	Y	stereo / mono	-	-	micro	2.0	Y	-	-
8.		Olympus E-M10 III	Y	stereo / mono	-	-	micro	2.0	Y	-	-
9.		Olympus E-P7	Y	stereo / mono	-	-	micro	2.0	Y	-	Y
10.		Olympus E-PL7	Y	stereo / mono	-	-	micro	2.0	Y	-	-
11.		Olympus E-PL8	Y	stereo / mono	-	-	micro	2.0	Y	-	-
12.		Olympus E-PL9	Y	stereo / mono	-	-	micro	2.0	Y	-	Y
13.		Olympus E-PL10	Y	stereo / mono	-	-	micro	2.0	Y	-	Y
14.		Olympus PEN-F	Y	stereo / mono	-	-	micro	2.0	Y	-	-
15.		Pentax K-500	Y	mono / mono	-	-	-	2.0	-	-	-
16.		Pentax K-S2	Y	mono / mono	Y	-	micro	2.0	Y	Y	-
17.		Sony A68	Y	stereo / mono	Y	-	micro	2.0	-	-	-

It is notable that the E-M10 IV offers wifi support, while the K-S1 does not. Wifi can be a very convenient means to transfer image data to an off-camera location.

The E-M10 IV 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 features and operation of the E-M10 IV and K-S1 can be found, respectively, in the Olympus E-M10 IV Manual (free pdf) or the online Pentax K-S1 Manual.

Review summary

So what conclusions can be drawn? Is there a clear favorite between the Olympus E-M10 IV and the Pentax K-S1? Which camera is better? A synthesis of the relative strong points of each of the models is listed below.

Advantages of the Olympus OM-D E-M10 Mark IV:

• Better video: Provides higher definition movie capture (4K/30p vs 1080/30p).
• More framing info: Has an electronic viewfinder that displays shooting data.
• More detailed LCD: Has a higher resolution rear screen (1040k vs 921k dots).
• More flexible LCD: Has a tilting screen for odd-angle shots in 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 burst: Shoots at higher frequency (15 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.
• Less heavy: Is lighter (by 175g or 31 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 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.
• Faster buffer clearing: Supports a more advanced SD data transfer standard (UHS-II vs UHS-I).
• More modern: Reflects 5 years and 11 months of technical progress since the K-S1 launch.

Arguments in favor of the Pentax K-S1:

• Brighter framing: Features an optical viewfinder for clear, lag-free composition.
• Larger viewfinder image: Features a viewfinder with a higher magnification (0.63x vs 0.62x).
• Faster shutter: Has higher mechanical shutter speed (1/6000s vs 1/4000s) to freeze action.
• Longer lasting: Gets more shots (410 versus 360) out of a single battery charge.
• 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-M10 IV is the clear winner of the match-up (16 : 5 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-M10 IV 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 the spec-sheets of cameras can offer a general idea of their imaging potential, it remains partial and cannot reveal, for example, the shooting experience and imaging performance when actually working with the E-M10 IV 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 hands-on reviews by experts 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], 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.		Olympus E-M10 IV	4.5/5	..	5/5	81/100	4.5/5	4.5/5	Aug 2020	699	amazon.com
2.		Pentax K-S1	4/5	..	..	..	4.5/5	4/5	Aug 2014	749	ebay.com
3.		Nikon D5300	4/5	+ +	..	79/100	4.5/5	4.5/5	Oct 2013	799	ebay.com
4.		Nikon D5500	5/5	+	..	79/100	4.5/5	4.5/5	Jan 2015	899	ebay.com
5.		Olympus E-M5 III	5/5	+	5/5	82/100	4.5/5	4.5/5	Oct 2019	1,199	ebay.com
6.		Olympus E-M10	4/5	..	..	80/100	5/5	5/5	Jan 2014	699	ebay.com
7.		Olympus E-M10 II	4.5/5	+ +	..	80/100	5/5	5/5	Aug 2015	649	ebay.com
8.		Olympus E-M10 III	..	+	5/5	80/100	4.5/5	4.5/5	Aug 2017	649	ebay.com
9.		Olympus E-P7	4/5	..	4.5/5	..	..	4.5/5	Jun 2021	799	amazon.com
10.		Olympus E-PL7	4/5	+	..	..	5/5	4/5	Aug 2014	599	ebay.com
11.		Olympus E-PL8	..	..	..	..	4.5/5	4/5	Sep 2016	549	ebay.com
12.		Olympus E-PL9	..	+	..	..	4.5/5	4/5	Feb 2018	599	ebay.com
13.		Olympus E-PL10	..	..	4/5	77/100	..	4/5	Oct 2019	599	ebay.com
14.		Olympus PEN-F	..	..	4/5	82/100	4.5/5	5/5	Jan 2016	1,199	ebay.com
15.		Pentax K-500	..	..	..	..	4.5/5	4.5/5	Jun 2013	549	ebay.com
16.		Pentax K-S2	4.5/5	..	..	..	5/5	4.5/5	Feb 2015	749	ebay.com
17.		Sony A68	3/5	..	..	..	4/5	4/5	Nov 2015	699	ebay.com
Note: (+ +) highly recommended; (+) recommended; (o) reviewed; (..) not available.

Care should be taken when interpreting the review scores above, though. The ratings are only valid when referring to cameras in the same category and of the same age. Hence, a score should always be seen in the context of the camera's market launch date and its price, and rating-comparisons among cameras that span long time periods or concern very differently equipped models make little sense. It should also be noted that some of the review sites have over time altered the way they render their verdicts.

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Other camera comparisons

Did this review help to inform your camera decision process? In case you would like to check on the differences and similarities of other camera models, just make your choice using the following search menu. There is also a set of direct links to comparison reviews that other users of the CAM-parator app explored.

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