Olympus E-M1 III vs Pentax K-S1
The Olympus OM-D E-M1 Mark III and the Pentax K-S1 are two digital cameras that were officially introduced, respectively, in February 2020 and August 2014. The E-M1 III is a mirrorless interchangeable lens camera, while the K-S1 is a DSLR. The cameras are based on a Four Thirds (E-M1 III) 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.
Going beyond this snapshot of core features and characteristics, what are the differences between the Olympus OM-D E-M1 Mark III 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.
The physical size and weight of the Olympus E-M1 III 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 K-S1 can be obtained in four different colors (black, grey, orange, white), while the E-M1 III is only available in black.
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 smaller (8 percent) than the Olympus E-M1 III. Moreover, the K-S1 is slightly lighter (4 percent) than the E-M1 III. It is worth mentioning in this context that the E-M1 III 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-M1 III gets 420 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. The power pack in the E-M1 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.
|1.||Olympus E-M1 III||134 mm||91 mm||69 mm||580 g||420||Y||Feb 2020||1,799|
|2.||Pentax K-S1||121 mm||93 mm||70 mm||558 g||410||n||Aug 2014||749|
|3.||Nikon D5300||125 mm||98 mm||76 mm||480 g||600||n||Oct 2013||799|
|4.||Olympus E-M10 IV||122 mm||84 mm||49 mm||383 g||360||n||Aug 2020||699|
|5.||Olympus E-M5 III||125 mm||85 mm||50 mm||414 g||310||Y||Oct 2019||1,199|
|6.||Olympus E-M1X||144 mm||147 mm||75 mm||997 g||870||Y||Jan 2019||2,999|
|7.||Olympus E-M1 II||134 mm||91 mm||67 mm||574 g||440||Y||Sep 2016||1,999|
|8.||Olympus E-M1||130 mm||94 mm||63 mm||497 g||350||Y||Sep 2013||1,399|
|9.||Panasonic G95||130 mm||94 mm||77 mm||536 g||290||Y||Apr 2019||999|
|10.||Panasonic G9||137 mm||97 mm||92 mm||658 g||400||Y||Nov 2017||1,699|
|11.||Panasonic GH5||139 mm||98 mm||87 mm||725 g||410||Y||Jan 2017||1,999|
|12.||Panasonic GX8||133 mm||78 mm||63 mm||487 g||330||Y||Jul 2015||1,199|
|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 A7C||124 mm||71 mm||60 mm||509 g||740||Y||Sep 2020||1,799|
|17.||Sony A68||143 mm||104 mm||81 mm||610 g||540||n||Nov 2015||699|
|Notes: Measurements and pricing do not include easily detachable parts, such as add-on or interchangeable lenses or optional viewfinders.|
Any camera decision will obviously take relative prices into account. 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-S1 was launched at a markedly lower price (by 58 percent) than the E-M1 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.
The size of the imaging sensor is a crucial determinant of image quality. A large sensor will generally have larger individual pixels that offer better low-light sensitivity, provide wider dynamic range, and have richer color-depth than smaller pixels 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 tend to be more expensive and lead to bigger and heavier cameras and lenses.
Of the two cameras under consideration, the Olympus E-M1 III 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-M1 III has a native 4:3 aspect ratio, while the one in the K-S1 offers a 3:2 aspect.
Technology-wise, both cameras are equipped with CMOS (Complementary Metal–Oxide–Semiconductor) sensors.
Despite having a smaller sensor, the Olympus E-M1 III 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-M1 III is much more recent (by 5 years and 5 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-M1 III 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-M1 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-M1 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-S1 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 following table provides an overview of the physical sensor characteristics, as well as the sensor quality measurements for a selection of comparators.
| DXO |
|1.||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-M5 III||Four Thirds||20.2||5184||3888||4K/30p||..||..||..||..|
|6.||Olympus E-M1X||Four Thirds||20.2||5184||3888||4K/30p||..||..||..||..|
|7.||Olympus E-M1 II||Four Thirds||20.2||5184||3888||4K/30p||23.7||12.8||1312||80|
|8.||Olympus E-M1||Four Thirds||15.9||4608||3456||1080/30p||23.0||12.7||757||73|
|9.||Panasonic G95||Four Thirds||20.2||5184||3888||4K/30p||..||..||..||..|
|10.||Panasonic G9||Four Thirds||20.2||5184||3888||4K/60p||..||..||..||..|
|11.||Panasonic GH5||Four Thirds||20.2||5184||3888||4K/60p||23.9||13.0||807||77|
|12.||Panasonic GX8||Four Thirds||20.2||5184||3888||4K/30p||23.5||12.6||806||75|
|16.||Sony A7C||Full Frame||24.0||6000||4000||4K/30p||25.0||14.7||3407||95|
Many modern cameras cannot only take still pictures, but also record videos. The two cameras under consideration both have sensors whose read-out speed is fast enough to capture moving pictures, but the E-M1 III 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.
Apart from body and sensor, cameras can and do differ across a variety of features. For example, the E-M1 III 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-M1 III has a higher magnification than the one of the K-S1 (0.74x 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 Olympus E-M1 III and Pentax K-S1 in connection with corresponding information for a sample of similar cameras.
|1.||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-M5 III||2360||n||3.0||1040||swivel||Y||1/8000s||10.0||n||Y|
|7.||Olympus E-M1 II||2360||n||3.0||1037||swivel||Y||1/8000s||18.0||n||Y|
One differentiating feature between the two cameras concerns the touch sensitivity of the rear screen. The E-M1 III 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 E-M1 III has an articulated LCD that can be turned to be front-facing. This characteristic will be appreciated by vloggers and photographers who are interested in snapping selfies. In contrast, the K-S1 does not have a selfie-screen.
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-M1 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-M1 III 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-M1 III and the K-S1 write their files to SDXC cards. The E-M1 III 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-M1 III supports UHS-II cards (on its first slot), while the K-S1 can use UHS-I cards.
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-M1 Mark III and Pentax K-S1 and, in particular, the interfaces the cameras (and selected comparators) provide for accessory control and data transfer.
| WiFi |
| NFC |
|1.||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-M5 III||Y||stereo||mono||Y||-||micro||2.0||Y||-||Y|
|7.||Olympus E-M1 II||Y||stereo||mono||Y||Y||micro||3.0||Y||-||-|
It is notable that the E-M1 III 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-M1 III (unlike the K-S1) features a PC Sync socket, so that professional strobe lights can be controlled by the camera.
The E-M1 III 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.
So what is the bottom line? Is there a clear favorite between the Olympus E-M1 III and the Pentax K-S1? Which camera is better? The listing below highlights the relative strengths of the two models.
Advantages of the Olympus OM-D E-M1 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.
- 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 (0.74x 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.
- 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.
- Faster data transfer: Supports a more advanced USB protocol (3.1 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 5 years and 5 months of technical progress since the K-S1 launch.
Reasons to prefer the Pentax K-S1:
- Brighter framing: Features an optical viewfinder for clear, lag-free composition.
- Easier fill-in: Has a small integrated flash to brighten shadows of backlit subjects.
- More affordable: Was introduced into a lower priced category (58 percent cheaper at launch).
- More heavily discounted: Has been around for much longer (launched in August 2014).
If the count of individual advantages (bullet points above) is taken as a guide, the E-M1 III is the clear winner of the match-up (25 : 4 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-M1 III 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 incomplete and does no justice, for example, to the way the E-M1 III or the K-S1 perform in practice. 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.
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], 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.
|1.||Olympus E-M1 III||5/5||..||83/100||4.5/5||4/5||Feb 2020||1,799|
|2.||Pentax K-S1||4/5||..||..||4.5/5||4/5||Aug 2014||749|
|3.||Nikon D5300||4/5||+ +||79/100||4.5/5||4.5/5||Oct 2013||799|
|4.||Olympus E-M10 IV||4.5/5||..||81/100||4.5/5||4.5/5||Aug 2020||699|
|5.||Olympus E-M5 III||5/5||+||82/100||4.5/5||4.5/5||Oct 2019||1,199|
|6.||Olympus E-M1X||4.5/5||o||..||4.5/5||..||Jan 2019||2,999|
|7.||Olympus E-M1 II||5/5||+ +||85/100||4.5/5||4.5/5||Sep 2016||1,999|
|8.||Olympus E-M1||5/5||+ +||84/100||4.5/5||4.5/5||Sep 2013||1,399|
|9.||Panasonic G95||4.5/5||+||83/100||4.5/5||4.5/5||Apr 2019||999|
|10.||Panasonic G9||..||+ +||85/100||5/5||5/5||Nov 2017||1,699|
|11.||Panasonic GH5||4.5/5||+ +||85/100||4.5/5||5/5||Jan 2017||1,999|
|12.||Panasonic GX8||5/5||+||82/100||4.5/5||4.5/5||Jul 2015||1,199|
|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 A7C||3.5/5||..||86/100||4/5||4/5||Sep 2020||1,799|
|17.||Sony A68||3/5||..||..||4/5||4/5||Nov 2015||699|
|Notes: (+ +) highly recommended; (+) recommended; (o) reviewed; (..) not available.|
Care should be taken when interpreting the review scores above, 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 comparisons of ratings among very different cameras or across long time periods have little meaning. 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 a corresponding selection in the search boxes below. Alternatively, you can follow any of the listed hyperlinks for comparisons that others found interesting.
Specifications: Olympus E-M1 III 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.
|Camera Model||Olympus E-M1 III||Pentax K-S1|
|Camera Type||Mirrorless system camera||Digital single lens reflex|
|Camera Lens||Micro Four Thirds lenses||Pentax K mount lenses|
|Launch Date||February 2020||August 2014|
|Launch Price||USD 1,799||USD 749|
|Sensor Specs||Olympus E-M1 III||Pentax K-S1|
|Sensor Format||Four Thirds Sensor||APS-C Sensor|
|Sensor Size||17.3 x 13.0 mm||23.5 x 15.6 mm|
|Sensor Area||224.9 mm2||366.6 mm2|
|Sensor Diagonal||21.6 mm||28.2 mm|
|Sensor Resolution||20.2 Megapixels||20 Megapixels|
|Image Resolution||5184 x 3888 pixels||5472 x 3648 pixels|
|Pixel Pitch||3.34 μm||4.28 μm|
|Pixel Density||8.96 MP/cm2||5.45 MP/cm2|
|Moiré control||no AA filter||no AA filter|
|Movie Capability||4K/30p Video||1080/30p Video|
|ISO Setting||200 - 25,600 ISO||100 - 51,200 ISO|
|ISO Boost||64 - 25,600 ISO||no Enhancement|
|Image Processor||TruePic IX||PRIME MII|
|DXO Sensor Quality (score)||..||78|
|DXO Color Depth (bits)||..||23.5|
|DXO Dynamic Range (EV)||..||13.0|
|DXO Low Light (ISO)||..||1061|
|Screen Specs||Olympus E-M1 III||Pentax K-S1|
|Viewfinder Type||Electronic viewfinder||Optical viewfinder|
|Viewfinder Field of View||100%||100%|
|Viewfinder Resolution||2360k dots|
|LCD Framing||Live View||Live View|
|Rear LCD Size||3.0inch||3.0inch|
|LCD Resolution||1037k dots||921k dots|
|LCD Attachment||Swivel screen||Fixed screen|
|Touch Input||Touchscreen||no Touchscreen|
|Shooting Specs||Olympus E-M1 III||Pentax K-S1|
|Focus System||On-Sensor Phase-detect||Phase-detect AF|
|Manual Focusing Aid||Focus Peaking||Focus Peaking|
|Max Shutter Speed (mechanical)||1/8000s||1/6000s|
|Continuous Shooting||18 shutter flaps/s||5.4 shutter flaps/s|
|Electronic Shutter||up to 1/32000s||no E-Shutter|
|Time-Lapse Photography||Intervalometer built-in||no Intervalometer|
|Image Stabilization||In-body stabilization||In-body stabilization|
|Fill Flash||no On-Board Flash||Build-in Flash|
|Storage Medium||SDXC cards||SDXC cards|
|Second Storage Option||Dual card slots||Single card slot|
|UHS card support||Single UHS-II||UHS-I|
|Connectivity Specs||Olympus E-M1 III||Pentax K-S1|
|Studio Flash||PC Sync socket||no PC Sync|
|USB Connector||USB 3.1||USB 2.0|
|HDMI Port||micro HDMI||micro HDMI|
|Microphone Port||External MIC port||no MIC socket|
|Headphone Socket||Headphone port||no Headphone port|
|Wifi Support||Wifi built-in||no Wifi|
|Bluetooth Support||Bluetooth built-in||no Bluetooth|
|Body Specs||Olympus E-M1 III||Pentax K-S1|
|Environmental Sealing||Weathersealed body||not weather sealed|
|Battery Life (CIPA)||420 shots per charge||410 shots per charge|
|In-Camera Charging||USB charging||no USB charging|
134 x 91 x 69 mm
(5.3 x 3.6 x 2.7 in)
121 x 93 x 70 mm
(4.8 x 3.7 x 2.8 in)
|Camera Weight||580 g (20.5 oz)||558 g (19.7 oz)|
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