Pentax K-S1 vs Sony A7 III
The Pentax K-S1 and the Sony Alpha A7 III are two digital cameras that were officially introduced, respectively, in August 2014 and February 2018. The K-S1 is a DSLR, while the A7 III is a mirrorless interchangeable lens camera. The cameras are based on an APS-C (K-S1) and a full frame (A7 III) sensor. The Pentax has a resolution of 20 megapixels, whereas the Sony provides 24 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 Pentax K-S1 and the Sony Alpha A7 III? 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 Pentax K-S1 and the Sony A7 III 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 width, height and depth dimensions are rounded to the nearest millimeter.
The K-S1 can be obtained in four different colors (black, grey, orange, white), while the A7 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 Sony A7 III is notably larger (8 percent) than the Pentax K-S1. Moreover, the A7 III is markedly heavier (16 percent) than the K-S1. It is noteworthy in this context that the A7 III is splash and dust-proof, 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 K-S1 gets 410 shots out of its D-LI109 battery, while the A7 III can take 610 images on a single charge of its NP-FZ100 power pack. The power pack in the A7 III can be charged via the USB port, which can be very convenient when travelling.
The table below summarizes the key physical specs of the two cameras alongside a broader set of comparators. If you want to switch the focus of the display and review another camera pair, you can move across to the CAM-parator tool and choose from the broad selection of possible camera comparisons there.
|1.||Pentax K-S1||121 mm||93 mm||70 mm||558 g||410||n||Aug 2014||749|
|2.||Sony A7 III||127 mm||96 mm||74 mm||650 g||610||Y||Feb 2018||1,999|
|3.||Canon 750D||132 mm||101 mm||78 mm||555 g||440||n||Feb 2015||749|
|4.||Canon 760D||132 mm||101 mm||78 mm||565 g||440||n||Feb 2015||649|
|5.||Nikon Z6||134 mm||101 mm||67 mm||675 g||310||Y||Aug 2018||1,999|
|6.||Nikon D5300||125 mm||98 mm||76 mm||480 g||600||n||Oct 2013||799|
|7.||Pentax K-S2||123 mm||91 mm||73 mm||678 g||410||Y||Feb 2015||749|
|8.||Pentax K-3 II||131 mm||100 mm||77 mm||800 g||720||Y||Apr 2015||1,099|
|9.||Pentax K-50||130 mm||97 mm||71 mm||650 g||410||Y||Jun 2013||599|
|10.||Pentax K-500||130 mm||97 mm||71 mm||646 g||710||n||Jun 2013||549|
|11.||Pentax K-3||131 mm||100 mm||77 mm||800 g||560||Y||Oct 2013||1,299|
|12.||Sony A7R IV||129 mm||96 mm||78 mm||665 g||670||Y||Jul 2019||3,499|
|13.||Sony A7R III||127 mm||96 mm||74 mm||650 g||650||Y||Oct 2017||3,199|
|14.||Sony A9||127 mm||96 mm||63 mm||673 g||650||Y||Apr 2017||4,499|
|15.||Sony A68||143 mm||104 mm||81 mm||610 g||540||n||Nov 2015||699|
|16.||Sony A7 II||127 mm||96 mm||60 mm||599 g||350||Y||Nov 2014||1,999|
|17.||Sony A58||129 mm||95 mm||78 mm||492 g||690||n||Feb 2013||599|
|Notes: Measurements and pricing do not include easily detachable parts, such as add-on or interchangeable lenses or optional viewfinders.|
The price is, of course, an important factor in any camera decision. The listed launch prices provide an indication of the market segment that the manufacturer of the cameras have been targeting. The K-S1 was launched at a markedly lower price (by 63 percent) than the A7 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 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 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 Pentax K-S1 features an APS-C sensor and the Sony A7 III a full frame sensor. The sensor area in the A7 III is 131 percent bigger. As a result of these sensor size differences, the cameras have a format factor of, respectively, 1.5 and 1.0. Both cameras have a native aspect ratio (sensor width to sensor height) of 3:2.
With 24MP, the A7 III offers a higher resolution than the K-S1 (20MP), but the A7 III nevertheless has larger individual pixels (pixel pitch of 5.94μm versus 4.28μm for the K-S1) due to its larger sensor. Moreover, the A7 III is a much more recent model (by 3 years and 6 months) than the K-S1, and its sensor will have benefitted from technological advances during this time that further enhance the light gathering capacity of its pixel-units. Coming back to sensor resolution, it should be mentioned that the K-S1 has no anti-alias filter installed, so that it can capture all the detail its sensor resolves.
The resolution advantage of the Sony A7 III implies greater flexibility for cropping images or the possibility to print larger pictures. The maximum print size of the A7 III for good quality output (200 dots per inch) amounts to 30 x 20 inches or 76.2 x 50.8 cm, for very good quality (250 dpi) 24 x 16 inches or 61 x 40.6 cm, and for excellent quality (300 dpi) 20 x 13.3 inches or 50.8 x 33.9 cm. The corresponding values for the Pentax K-S1 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.
The A7 III has on-sensor phase detect pixels, which results in fast and reliable autofocus acquisition even during live view operation.
The Pentax K-S1 has a native sensitivity range from ISO 100 to ISO 51200. The corresponding ISO settings for the Sony Alpha A7 III are ISO 100 to ISO 51200, with the possibility to increase the ISO range to 50-204800.
Consistent information on actual sensor performance is available from DXO Mark for many cameras. 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. Of the two cameras under consideration, the A7 III offers substantially better image quality than the K-S1 (overall score 18 points higher). The advantage is based on 1.5 bits higher color depth, 1.7 EV in additional dynamic range, and 1.8 stops in additional low light sensitivity. The table below summarizes the physical sensor characteristics and sensor quality findings and compares them across a set of similar cameras.
| DXO |
|2.||Sony A7 III||Full Frame||24.0||6000||4000||4K/30p||25.0||14.7||3730||96|
|5.||Nikon Z6||Full Frame||24.3||6048||4024||4K/30p||25.3||14.3||3299||95|
|8.||Pentax K-3 II||APS-C||24.1||6016||4000||1080/60i||23.6||13.6||1106||80|
|12.||Sony A7R IV||Full Frame||60.2||9504||6336||4K/30p||26.0||14.8||3344||99|
|13.||Sony A7R III||Full Frame||42.2||7952||5304||4K/30p||26.0||14.7||3523||100|
|14.||Sony A9||Full Frame||24.0||6000||4000||4K/30p||24.9||13.3||3517||92|
|16.||Sony A7 II||Full Frame||24.0||6000||4000||1080/60p||24.9||13.6||2449||90|
Many modern cameras are not only capable of taking still images, but also of capturing video footage. Both cameras under consideration have a sensor with sufficiently fast read-out times for moving pictures, but the A7 III provides a better video resolution than the K-S1. It can shoot movie footage at 4K/30p, while the Pentax is limited to 1080/30p.
Beyond body and sensor, cameras can and do differ across a range of features. For example, the A7 III has an electronic viewfinder (2359k 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 A7 III has a higher magnification than the one of the K-S1 (0.78x 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 Pentax K-S1 and Sony A7 III along with similar information for a selection of comparators.
|2.||Sony A7 III||2359||n||3.0||922||tilting||Y||1/8000s||10.0||n||Y|
|8.||Pentax K-3 II||optical||Y||3.2||1037||fixed||n||1/8000s||8.3||n||Y|
|12.||Sony A7R IV||5760||n||3.0||1440||tilting||Y||1/8000s||10.0||n||Y|
|13.||Sony A7R III||3686||n||3.0||1440||tilting||Y||1/8000s||10.0||n||Y|
|16.||Sony A7 II||2400||n||3.0||1230||tilting||n||1/8000s||5.0||n||Y|
One difference between the cameras concerns the presence of an on-board flash. The K-S1 has one, while the A7 III does not. While the built-in flash of the K-S1 is not very powerful, it can at times be useful as a fill-in light.
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 A7 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 Sony A7 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.
The K-S1 writes its imaging data to SDXC cards, while the A7 III uses SDXC or Memory Stick PRO Duo cards. The A7 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 A7 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 Pentax K-S1 and Sony Alpha A7 III and, in particular, the interfaces the cameras (and selected comparators) provide for accessory control and data transfer.
| WiFi |
| NFC |
|2.||Sony A7 III||Y||stereo||mono||Y||Y||micro||3.1||Y||Y||Y|
|8.||Pentax K-3 II||Y||mono||mono||Y||Y||mini||3.0||-||-||-|
|12.||Sony A7R IV||Y||stereo||mono||Y||Y||micro||3.1||Y||Y||Y|
|13.||Sony A7R III||Y||stereo||mono||Y||Y||micro||3.1||Y||Y||Y|
|16.||Sony A7 II||Y||stereo||mono||Y||Y||micro||2.0||Y||Y||-|
It is notable that the A7 III offers wifi support, which can be a very convenient means to transfer image data to an off-camera location. In contrast, the K-S1 does not provide wifi capability.
The A7 III is a recent model that features in the current product line-up of Sony. 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 Pentax and Sony websites.
So what is the bottom line? Is the Pentax K-S1 better than the Sony A7 III or vice versa? Below is a summary of the relative strengths of each of the two contestants.
Advantages of the Pentax K-S1:
- Maximized detail: Lacks an anti-alias filter to exploit the sensor's full resolution potential.
- Brighter framing: Features an optical viewfinder for clear, lag-free composition.
- Less heavy: Is lighter (by 92g or 14 percent) and hence easier to carry around.
- Easier fill-in: Is equipped with a small onboard flash to brighten deep shadow areas.
- More affordable: Was introduced into a lower priced category (63 percent cheaper at launch).
- More heavily discounted: Has been available for much longer (launched in August 2014).
Arguments in favor of the Sony Alpha A7 III:
- More detail: Has more megapixels (24 vs 20MP), which boosts linear resolution by 10%.
- Better moiré control: Has an anti-alias filter to avoid artificial patterns to appear in images.
- Better image quality: Scores substantially higher (18 points) in the DXO overall evaluation.
- Richer colors: Generates noticeably more natural colors (1.5 bits more color depth).
- More dynamic range: Captures a broader range of light and dark details (1.7 EV of extra DR).
- Better low-light sensitivity: Can shoot in dim conditions (1.8 stops ISO advantage).
- 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 (0.78x vs 0.63x).
- More flexible LCD: Has a tilting screen for odd-angle shots in landscape orientation.
- Fewer buttons to press: Has a touchscreen to facilitate handling and shooting adjustments.
- 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.
- Easier time-lapse photography: Has an intervalometer built-in for low frequency shooting.
- Longer lasting: Gets more shots (610 versus 410) out of a single battery charge.
- Easier travel charging: Can be conveniently charged via its USB port.
- Better sealing: Is splash and dust sealed for shooting in inclement weather conditions.
- More legacy lens friendly: Can use many 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 device pairing: Supports NFC for fast wireless image transfer over short distances.
- Easier wireless transfer: Supports Bluetooth for image sharing without cables.
- 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 3 years and 6 months of technical progress since the K-S1 launch.
If the count of individual advantages (bullet points above) is taken as a guide, the A7 III is the clear winner of the contest (29 : 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 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-S1 and the Sony A7 III place the cameras among the top in their class? Find out in the latest Best DSLR Camera and Best Mirrorless Interchangeable Lens Camera listings 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 says little about, for example, the shooting experience and imaging performance of the K-S1 and the A7 III 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.
This is why hands-on reviews by experts are important. 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.||Pentax K-S1||4/5||..||..||4.5/5||4/5||Aug 2014||749|
|2.||Sony A7 III||..||+ +||89/100||5/5||5/5||Feb 2018||1,999|
|3.||Canon 750D||5/5||..||75/100||4.5/5||4.5/5||Feb 2015||749|
|4.||Canon 760D||5/5||+||77/100||4.5/5||4.5/5||Feb 2015||649|
|5.||Nikon Z6||5/5||..||..||4.5/5||5/5||Aug 2018||1,999|
|6.||Nikon D5300||4/5||+ +||79/100||4.5/5||4.5/5||Oct 2013||799|
|7.||Pentax K-S2||4.5/5||..||..||5/5||4.5/5||Feb 2015||749|
|8.||Pentax K-3 II||4.5/5||..||..||5/5||5/5||Apr 2015||1,099|
|9.||Pentax K-50||5/5||..||..||5/5||4.5/5||Jun 2013||599|
|10.||Pentax K-500||..||..||..||4.5/5||4.5/5||Jun 2013||549|
|11.||Pentax K-3||4/5||..||83/100||5/5||5/5||Oct 2013||1,299|
|12.||Sony A7R IV||5/5||+||91/100||4.5/5||5/5||Jul 2019||3,499|
|13.||Sony A7R III||..||+ +||90/100||4.5/5||5/5||Oct 2017||3,199|
|14.||Sony A9||5/5||+ +||89/100||5/5||5/5||Apr 2017||4,499|
|15.||Sony A68||3/5||..||..||4/5||4/5||Nov 2015||699|
|16.||Sony A7 II||5/5||+||82/100||4.5/5||5/5||Nov 2014||1,999|
|17.||Sony A58||3/5||..||..||4.5/5||4.5/5||Feb 2013||599|
|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. A score, therefore, has to be seen in close connection to the price and market introduction time 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 would like to check on the differences and similarities of other camera models, just use the search menu below. As an alternative, you can also directly jump to any one of the listed comparisons that were previously generated by the CAM-parator tool.
Specifications: Pentax K-S1 vs Sony A7 III
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||Pentax K-S1||Sony A7 III|
|Camera Type||Digital single lens reflex||Mirrorless system camera|
|Camera Lens||Pentax K mount lenses||Sony E mount lenses|
|Launch Date||August 2014||February 2018|
|Launch Price||USD 749||USD 1,999|
|Sensor Specs||Pentax K-S1||Sony A7 III|
|Sensor Format||APS-C Sensor||Full Frame Sensor|
|Sensor Size||23.5 x 15.6 mm||35.6 x 23.8 mm|
|Sensor Area||366.6 mm2||847.28 mm2|
|Sensor Diagonal||28.2 mm||42.8 mm|
|Sensor Resolution||20 Megapixels||24 Megapixels|
|Image Resolution||5472 x 3648 pixels||6000 x 4000 pixels|
|Pixel Pitch||4.28 μm||5.94 μm|
|Pixel Density||5.45 MP/cm2||2.83 MP/cm2|
|Moiré control||no AA filter||Anti-Alias filter|
|Movie Capability||1080/30p Video||4K/30p Video|
|ISO Setting||100 - 51,200 ISO||100 - 51,200 ISO|
|ISO Boost||no Enhancement||50 - 204,800 ISO|
|Image Processor||PRIME MII||BIONZ X|
|DXO Sensor Quality (score)||78||96|
|DXO Color Depth (bits)||23.5||25.0|
|DXO Dynamic Range (EV)||13.0||14.7|
|DXO Low Light (ISO)||1061||3730|
|Screen Specs||Pentax K-S1||Sony A7 III|
|Viewfinder Type||Optical viewfinder||Electronic viewfinder|
|Viewfinder Field of View||100%||100%|
|Viewfinder Resolution||2359k dots|
|LCD Framing||Live View||Live View|
|Rear LCD Size||3.0inch||3.0inch|
|LCD Resolution||921k dots||922k dots|
|LCD Attachment||Fixed screen||Tilting screen|
|Touch Input||no Touchscreen||Touchscreen|
|Shooting Specs||Pentax K-S1||Sony A7 III|
|Focus System||Phase-detect AF||On-Sensor Phase-detect|
|Manual Focusing Aid||Focus Peaking||Focus Peaking|
|Max Shutter Speed (mechanical)||1/6000s||1/8000s|
|Continuous Shooting||5.4 shutter flaps/s||10 shutter flaps/s|
|Electronic Shutter||no E-Shutter||YES|
|Time-Lapse Photography||no Intervalometer||Intervalometer built-in|
|Image Stabilization||In-body stabilization||In-body stabilization|
|Fill Flash||Build-in Flash||no On-Board Flash|
|Storage Medium||SDXC cards||MS or SDXC cards|
|Second Storage Option||Single card slot||Dual card slots|
|UHS card support||UHS-I||Single UHS-II|
|Connectivity Specs||Pentax K-S1||Sony A7 III|
|USB Connector||USB 2.0||USB 3.1|
|HDMI Port||micro HDMI||micro HDMI|
|Microphone Port||no MIC socket||External MIC port|
|Headphone Socket||no Headphone port||Headphone port|
|Wifi Support||no Wifi||Wifi built-in|
|Near-Field Communication||no NFC||NFC built-in|
|Bluetooth Support||no Bluetooth||Bluetooth built-in|
|Body Specs||Pentax K-S1||Sony A7 III|
|Environmental Sealing||not weather sealed||Weathersealed body|
|Battery Life (CIPA)||410 shots per charge||610 shots per charge|
|In-Camera Charging||no USB charging||USB charging|
121 x 93 x 70 mm
(4.8 x 3.7 x 2.8 in)
127 x 96 x 74 mm
(5.0 x 3.8 x 2.9 in)
|Camera Weight||558 g (19.7 oz)||650 g (22.9 oz)|
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