Pentax K-3 vs Sony A7 III
The Pentax K-3 and the Sony Alpha A7 III are two enthusiast cameras that were revealed to the public, respectively, in October 2013 and February 2018. The K-3 is a DSLR, while the A7 III is a mirrorless interchangeable lens camera. The cameras are based on an APS-C (K-3) and a full frame (A7 III) sensor. The Pentax has a resolution of 24.1 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.
|Pentax K-3||Sony A7 III|
|Digital single lens reflex||Mirrorless system camera|
|Pentax K mount lenses||Sony E mount lenses|
|24.1 MP, APS-C Sensor||24 MP, Full Frame Sensor|
|1080/60i Video||4K/30p Video|
|ISO 100-51,200||ISO 100-51,200 (50 - 204,800)|
|Optical viewfinder||Electronic viewfinder (2359k dots)|
|3.2 LCD, 1037k dots||3.0 LCD, 922k dots|
|Fixed screen (not touch-sensitive)||Tilting touchscreen|
|8.3 shutter flaps per second||10 shutter flaps per second|
|In-body stabilization||In-body stabilization|
|Weathersealed body||Weathersealed body|
|560 shots per battery charge||610 shots per battery charge|
|131 x 100 x 77 mm, 800 g||127 x 96 x 74 mm, 650 g|
Going beyond this snapshot of core features and characteristics, what are the differences between the Pentax K-3 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.
An illustration of the physical size and weight of the Pentax K-3 and the Sony A7 III is provided 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 measures are rounded to the nearest millimeter.
The K-3 can be obtained in two different colors (black, silver), 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 smaller (7 percent) than the Pentax K-3. Moreover, the A7 III is markedly lighter (19 percent) than the K-3. 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 K-3 gets 560 shots out of its D-LI90 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 adjacent table lists the principal physical characteristics of the two cameras alongside a wider set of alternatives. In case you want to display and compare another camera duo, just click on the right or left arrow next to the camera that you would like to inspect. Alternatively, you can also use the CAM-parator to select your camera combination among a larger number of options.
|Pentax K-3||5.2 in||3.9 in||3.0 in||28.2 oz||560||Y||Oct 2013||1,299|
|Sony A7 III||5.0 in||3.8 in||2.9 in||22.9 oz||610||Y||Feb 2018||1,999|
|Canon 6D Mark II||5.7 in||4.4 in||3.0 in||27.0 oz||1200||Y||Jun 2017||1,999|
|Canon 70D||5.5 in||4.1 in||3.1 in||26.6 oz||920||Y||Jul 2013||1,199|
|Nikon D7200||5.4 in||4.2 in||3.0 in||27.0 oz||1110||Y||Mar 2015||1,199|
|Nikon D7100||5.4 in||4.2 in||3.0 in||27.0 oz||950||Y||Feb 2013||1,199|
|Pentax KP||5.2 in||4.0 in||3.0 in||24.8 oz||390||Y||Jan 2017||1,099|
|Pentax K-70||5.0 in||3.7 in||2.9 in||24.3 oz||410||Y||Jun 2016||649|
|Pentax K-3 II||5.2 in||3.9 in||3.0 in||28.2 oz||720||Y||Apr 2015||1,099|
|Pentax K-5||5.2 in||3.8 in||2.9 in||26.8 oz||740||Y||Sep 2010||1,099|
|Sony A9 II||5.1 in||3.8 in||3.0 in||23.9 oz||690||Y||Oct 2019||4,499|
|Sony A9||5.0 in||3.8 in||2.5 in||23.7 oz||650||Y||Apr 2017||4,499|
|Sony A6500||4.7 in||2.6 in||2.1 in||16.0 oz||350||Y||Oct 2016||1,399|
|Sony A7 II||5.0 in||3.8 in||2.4 in||21.1 oz||350||Y||Nov 2014||1,999|
|Sony A7||5.0 in||3.7 in||1.9 in||16.7 oz||340||Y||Oct 2013||1,699|
|Sony A99||5.8 in||4.4 in||3.1 in||28.6 oz||500||Y||Sep 2012||2,799|
|Sony A77||5.6 in||4.1 in||3.2 in||25.8 oz||470||Y||Aug 2011||1,399|
Notes: Measurements and pricing do not include easily detachable parts, such as add-on or interchangeable lenses or optional viewfinders.
(1) Number of images that can be taken on a full battery charge according to the CIPA-standard; (2) Official announcement.
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 K-3 was launched at a markedly lower price (by 35 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 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 Pentax K-3 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.
Despite having a smaller sensor, the Pentax K-3 offers a higher resolution of 24.1 megapixels, compared with 24 MP of the Sony A7 III. 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 3.90μm versus 5.94μm for the A7 III). Moreover, it should be noted that the A7 III is much more recent (by 4 years and 4 months) than the K-3, 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-3 has no anti-alias filter installed, so that it can capture all the detail its sensor resolves.
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-3 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-3 (overall score 16 points higher). The advantage is based on 1.3 bits higher color depth, 1.3 EV in additional dynamic range, and 1.6 stops in additional low light sensitivity. The adjacent table reports on the physical sensor characteristics and the outcomes of the DXO sensor quality tests for a sample of comparator-cameras.
|Sony A7 III||Full Frame||24.0||6000||4000||4K/30p||25.0||14.7||3730||96|
|Canon 6D Mark II||Full Frame||26.0||6240||4160||1080/60p||24.4||11.9||2862||85|
|Pentax K-3 II||APS-C||24.1||6016||4000||1080/60i||23.6||13.6||1106||80|
|Sony A9 II||Full Frame||24.0||6000||4000||4K/30p||25.0||14.0||3434||93|
|Sony A9||Full Frame||24.0||6000||4000||4K/30p||24.9||13.3||3517||92|
|Sony A7 II||Full Frame||24.0||6000||4000||1080/60p||24.9||13.6||2449||90|
|Sony A7||Full Frame||24.0||6000||4000||1080/60p||24.8||14.2||2248||90|
|Sony A99||Full Frame||24.0||6000||4000||1080/60p||25.0||14.0||1555||89|
Many modern cameras are not only capable of taking still images, but can also record movies. Both cameras under consideration are equipped with sensors that have a sufficiently high read-out speed for moving images, but the A7 III provides a better video resolution than the K-3. It can shoot movie footage at 4K/30p, while the Pentax is limited to 1080/60i.
Apart from 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-3 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-3 (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 following table reports on some other key feature differences and similarities of the Pentax K-3, the Sony A7 III, and comparable cameras.
|Sony A7 III||2359||n||3.0||922||tilting||Y||1/8000s||10.0||n||Y|
|Canon 6D Mark II||optical||Y||3.0||1040||swivel||Y||1/4000s||6.5||n||n|
|Pentax K-3 II||optical||Y||3.2||1037||fixed||n||1/8000s||8.3||n||Y|
|Sony A9 II||3686||n||3.0||1440||tilting||Y||1/8000s||10.0||n||Y|
|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-3 has one, while the A7 III does not. While the built-in flash of the K-3 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 Pentax K-3 and the Sony A7 III 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.
The K-3 writes its imaging data to SDXC cards, while the A7 III uses SDXC or Memory Stick PRO Duo cards. Both cameras feature dual card slots, which can be very useful in case a memory card fails. The A7 III supports UHS-II cards (on its first slot), while the K-3 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-3 and Sony Alpha A7 III and, in particular, the interfaces the cameras (and selected comparators) provide for accessory control and data transfer.
| WiFi |
|Sony A7 III||Y||stereo||mono||Y||Y||micro||3.1||Y||Y||Y|
|Canon 6D Mark II||Y||stereo||mono||Y||-||mini||2.0||Y||Y||Y|
|Pentax K-3 II||Y||mono||mono||Y||Y||mini||3.0||-||-||-|
|Sony A9 II||Y||stereo||mono||Y||Y||micro||3.1||Y||Y||Y|
|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-3 does not provide wifi capability.
Studio photographers will appreciate that the Pentax K-3 (unlike the A7 III) features a PC Sync socket, so that professional strobe lights can be controlled by the camera.
The A7 III is a recent model that features in the current product line-up of Sony. In contrast, the K-3 has been discontinued (but can be found pre-owned on eBay). As a replacement in the same line of cameras, the K-3 was succeeded by the Pentax K-3 II. 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 how do things add up? Is the Pentax K-3 better than the Sony A7 III or vice versa? Below is a summary of the relative strengths of each of the two contestants.
Arguments in favor of the Pentax K-3:
- 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.
- Easier setting verification: Features an LCD display on top to control shooting parameters.
- Larger screen: Has a bigger rear LCD (3.2" vs 3.0") for image review and settings control.
- More detailed LCD: Has a higher resolution rear screen (1037k vs 922k dots).
- Easier fill-in: Is equipped with a small onboard flash to brighten deep shadow areas.
- Better studio light control: Has a PC Sync socket to connect to professional strobe lights.
- More affordable: Was introduced into a lower priced category (35 percent cheaper at launch).
- More heavily discounted: Has been available for much longer (launched in October 2013).
Reasons to prefer the Sony Alpha A7 III:
- Better moiré control: Has an anti-alias filter to avoid artificial patterns to appear in images.
- Better image quality: Scores substantially higher (16 points) in the DXO overall evaluation.
- Richer colors: Generates noticeably more natural colors (1.3 bits more color depth).
- More dynamic range: Captures a broader range of light and dark details (1.3 EV of extra DR).
- Better low-light sensitivity: Can shoot in dim conditions (1.6 stops ISO advantage).
- Better video: Provides higher definition movie capture (4K/30p vs 1080/60i).
- 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 (0.78x 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 burst: Shoots at higher frequency (10 vs 8.3 flaps/sec) to capture the decisive moment.
- Less disturbing: Has an electronic shutter option for completely silent shooting.
- Less heavy: Has a lower weight (by 150g or 19 percent) and is thus easier to take along.
- Easier travel charging: Can be conveniently charged via its USB port.
- More legacy lens friendly: Can use many non-native lenses via adapters.
- 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.
- 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-3 launch.
If the number of relative strengths (bullet points above) is taken as a guide, the A7 III is the clear winner of the contest (20 : 9 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 Pentax K-3 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 comparison of technical specifications can provide a useful overview of the capabilities of different cameras, it says little about, for example, the shooting experience and imaging performance of the K-3 and the A7 III in practical situations. 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.
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 (cameralabs, dpreview, ephotozine, imaging-resource, and photographyblog). 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.
|Pentax K-3||..||83/100||5/5||4.5/5||5/5||Oct 2013||1,299|
|Sony A7 III||+ +||89/100||5/5||5/5||5/5||Feb 2018||1,999|
|Canon 6D Mark II||+||80/100||4.5/5||4/5||4/5||Jun 2017||1,999|
|Canon 70D||+ +||83/100||4.5/5||4.5/5||5/5||Jul 2013||1,199|
|Nikon D7200||+ +||84/100||4.5/5||4/5||4.5/5||Mar 2015||1,199|
|Nikon D7100||+ +||85/100||4.5/5||5/5||4.5/5||Feb 2013||1,199|
|Pentax KP||..||82/100||5/5||..||4.5/5||Jan 2017||1,099|
|Pentax K-70||..||79/100||4.5/5||4/5||4.5/5||Jun 2016||649|
|Pentax K-3 II||..||..||5/5||4.5/5||5/5||Apr 2015||1,099|
|Pentax K-5||..||83/100||5/5||4.5/5||4.5/5||Sep 2010||1,099|
|Sony A9 II||..||90/100||5/5||..||5/5||Oct 2019||4,499|
|Sony A9||+ +||89/100||5/5||5/5||5/5||Apr 2017||4,499|
|Sony A6500||+ +||85/100||4.5/5||5/5||4.5/5||Oct 2016||1,399|
|Sony A7 II||+||82/100||4.5/5||5/5||5/5||Nov 2014||1,999|
|Sony A7||+ +||80/100||5/5||4.5/5||5/5||Oct 2013||1,699|
|Sony A99||..||84/100||4.5/5||o||4.5/5||Sep 2012||2,799|
|Sony A77||91/100||81/100||..||4.5/5||5/5||Aug 2011||1,399|
|Notes: (+ +) highly recommended; (+) recommended; (o) reviewed; (..) not available.|
The review scores listed above should be treated 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. 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 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.
- Canon 1Ds vs Pentax K-3 II
- Canon 200D vs Pentax K-3 II
- Canon 300D vs Sony A7 III
- Canon 7D vs Pentax K-3 II
- Canon G7 X vs Pentax K-3
- Canon T2i vs Pentax K-3
- Contax N Digital vs Pentax K-3
- Fujifilm X-A1 vs Pentax K-3 II
- Leica M8 vs Pentax K-3
- Leica X2 vs Pentax K-3 II
- Nikon D100 vs Sony A7 III
- Nikon D40X vs Pentax K-3 II
Specifications: Pentax K-3 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-3||Sony A7 III|
|Camera Type||Digital single lens reflex||Mirrorless system camera|
|Camera Lens||Pentax K mount lenses||Sony E mount lenses|
|Launch Date||October 2013||February 2018|
|Launch Price||USD 1,299||USD 1,999|
|Sensor Specs||Pentax K-3||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||24.1 Megapixels||24 Megapixels|
|Image Resolution||6016 x 4000 pixels||6000 x 4000 pixels|
|Pixel Pitch||3.90 μm||5.94 μm|
|Pixel Density||6.56 MP/cm2||2.83 MP/cm2|
|Moiré control||no AA filter||Anti-Alias filter|
|Movie Capability||1080/60i 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 III||BIONZ X|
|DXO Sensor Quality (score)||80||96|
|DXO Color Depth (bits)||23.7||25.0|
|DXO Dynamic Range (EV)||13.4||14.7|
|DXO Low Light (ISO)||1216||3730|
|Screen Specs||Pentax K-3||Sony A7 III|
|Viewfinder Type||Optical viewfinder||Electronic viewfinder|
|Viewfinder Field of View||100%||100%|
|Viewfinder Resolution||2359k dots|
|Top-Level Screen||Control Panel||no Top Display|
|LCD Framing||Live View||Live View|
|Rear LCD Size||3.2inch||3.0inch|
|LCD Resolution||1037k dots||922k dots|
|LCD Attachment||Fixed screen||Tilting screen|
|Touch Input||no Touchscreen||Touchscreen|
|Shooting Specs||Pentax K-3||Sony A7 III|
|Focus System||Phase-detect AF||On-Sensor Phase-detect|
|Manual Focusing Aid||Focus Peaking||Focus Peaking|
|Max Shutter Speed (mechanical)||1/8000s||1/8000s|
|Continuous Shooting||8.3 shutter flaps/s||10 shutter flaps/s|
|Shutter Life Expectancy||200 000 actuations||200 000 actuations|
|Electronic Shutter||no E-Shutter||YES|
|Time-Lapse Photography||Intervalometer built-in||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||Dual card slots||Dual card slots|
|UHS card support||UHS-I||Single UHS-II|
|Connectivity Specs||Pentax K-3||Sony A7 III|
|Studio Flash||PC Sync socket||no PC Sync|
|USB Connector||USB 3.0||USB 3.1|
|HDMI Port||mini HDMI||micro HDMI|
|Microphone Port||External MIC port||External MIC port|
|Headphone Socket||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-3||Sony A7 III|
|Environmental Sealing||Weathersealed body||Weathersealed body|
|Battery Life (CIPA)||560 shots per charge||610 shots per charge|
|In-Camera Charging||no USB charging||USB charging|
131 x 100 x 77 mm
(5.2 x 3.9 x 3.0 in)
127 x 96 x 74 mm
(5.0 x 3.8 x 2.9 in)
|Camera Weight||800 g (28.2 oz)||650 g (22.9 oz)|
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