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Pentax K-3 II versus Sony A7R III

The Pentax K-3 II and the Sony Alpha A7R III are two enthusiast cameras that were announced, respectively, in April 2015 and October 2017. The K-3 II is a DSLR, while the A7R III is a mirrorless interchangeable lens camera. The cameras are based on an APS-C (K-3 II) and a full frame (A7R III) sensor. The Pentax has a resolution of 24.1 megapixel, whereas the Sony provides 42.2 MP. Read on to find out how these two cameras compare with respect to their size, their sensors, their features, and their reception by expert reviewers.

Body comparison: Pentax K-3 II vs Sony A7R III

The side-by-side display below illustrates the physical size and weight of the Pentax K-3 II and the Sony A7R III. 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 width, height and depth measures are rounded to the nearest millimeter. You can also use the toggle button to switch to a percentage comparison if you prefer that the measures are being expressed in relative terms (in this case, the camera on the left side – the K-3 II – represents the basis for the calculations across all the size and weight measures).

Compare Pentax K-3 II vs Sony A7R III
Compare K-3 II versus A7R III top
Compare K-3 II and A7R III rear

If the front view area (width x height) of the cameras is taken as an aggregate measure of their size, the Sony A7R III is notably smaller (7 percent) than the Pentax K-3 II. Moreover, the A7R III is markedly lighter (19 percent) than the K-3 II. 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 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 II gets 720 shots out of its D-LI90 battery, while the A7R III can take 650 images on a single charge of its NP-FZ100 power pack.

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, just use the right or left arrows in the table to switch to the respective camera. Alternatively, you can also navigate to the CAM-parator app and make your selection from the full list of cameras there.

Camera Body Specifications
  Camera
Model
Camera
Width
Camera
Height
Camera
Depth
Camera
Weight
Battery
Life
(CIPA)
Weather
Sealing
(yes/no)
Camera
Launch
(announced)
Launch
Price
(USD)
Street
Price
(USD)
Used
Price
(USD)
Camera
Model
Pentax K-3 II» 5.2 in 3.9 in 3.0 in 28.2 oz 720 Y Apr 2015 1,099 i i Pentax K-3 II
Sony A7R III« 5.0 in 3.8 in 2.9 in 22.9 oz 650 Y Oct 2017 3,199 i i Sony A7R III
Canon 80D« » 5.5 in 4.1 in 3.1 in 25.8 oz 960 Y Feb 2016 1,199 i i Canon 80D
Nikon D7200« » 5.4 in 4.2 in 3.0 in 27.0 oz 1110 Y Mar 2015 1,199- i Nikon D7200
Panasonic GX8« » 5.2 in 3.1 in 2.5 in 17.2 oz 330 Y Jul 2015 1,199- i Panasonic GX8
Pentax KP« » 5.2 in 4.0 in 3.0 in 24.8 oz 390 Y Jan 2017 1,099 i i Pentax KP
Pentax K-70« » 5.0 in 3.7 in 2.9 in 24.3 oz 410 Y Jun 2016 649 i i Pentax K-70
Pentax K-3« » 5.2 in 3.9 in 3.0 in 28.2 oz 560 Y Oct 2013 1,299- i Pentax K-3
Pentax K-5« » 5.2 in 3.8 in 2.9 in 26.8 oz 740 Y Sep 2010 1,099- i Pentax K-5
Sony A7 III« » 5.0 in 3.8 in 2.9 in 22.9 oz 610 Y Feb 2018 1,999 i i Sony A7 III
Sony A9« » 5.0 in 3.8 in 2.5 in 23.7 oz 650 Y Apr 2017 4,499 i i Sony A9
Sony A99 II« » 5.6 in 4.1 in 3.0 in 29.9 oz 490 Y Sep 2016 3,199 i i Sony A99 II
Sony A6300« » 4.7 in 2.6 in 1.9 in 14.3 oz 400 Y Feb 2016 999- i Sony A6300
Sony A6500« » 4.7 in 2.6 in 2.1 in 16.0 oz 350 Y Oct 2016 1,399 i i Sony A6500
Sony A7R II« » 5.0 in 3.8 in 2.4 in 22.0 oz 290 Y Jun 2015 3,199- i Sony A7R II
Sony A7S II« » 5.0 in 3.8 in 2.4 in 22.1 oz 370 Y Sep 2015 2,999 i i Sony A7S II
Sony RX10 II« » 5.1 in 3.5 in 4.0 in 28.7 oz 400 Y Jun 2015 1,299- i Sony RX10 II

Any camera purchase will naturally be influenced heavily by the price. 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-3 II was launched at a markedly lower price (by 66 percent) than the A7R 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.

 

Sensor comparison: Pentax K-3 II vs Sony A7R III

The size of the sensor inside a digital camera is one of the key determinants 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. 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 tend to be more expensive and lead to bigger and heavier cameras and lenses.

Of the two cameras under consideration, the Pentax K-3 II features an APS-C sensor and the Sony A7R III a full frame sensor. The sensor area in the A7R III is 135 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.

Pentax K-3 II and Sony A7R III sensor measures

With 42.2MP, the A7R III offers a higher resolution than the K-3 II (24.1MP), but the A7R III nevertheless has larger individual pixels (pixel pitch of 4.52μm versus 3.90μm for the K-3 II) due to its larger sensor. Moreover, the A7R III is a much more recent model (by 2 years and 6 months) than the K-3 II, 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 neither of the two cameras has an anti-alias filter installed, so they are able to capture all the detail the sensor resolves.

Both cameras have the capacity to capture high quality composite images by combining multiple shots after shifting the sensor by miniscule distances. This multi-shot, pixel-shift mode is most suitable for photography of stationary objects (landscapes, studio scenes).

K-3 II versus A7R III MP

For many cameras, data on sensor performance has been reported by DXO Mark. 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 A7R III offers substantially better image quality than the K-3 II (overall score 20 points higher). The advantage is based on 2.4 bits higher color depth, 1.1 EV in additional dynamic range, and 1.7 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.

Sensor Characteristics
  Camera
Model
Sensor
Class
Resolution
(MP)
Horiz.
Pixels
Vert.
Pixels
Video
Format
DXO
Portrait
DXO
Landscape
DXO
Sports
DXO
Overall
Camera
Model
Pentax K-3 II» APS-C 24.1 6016 40001080/60i23.613.6110680Pentax K-3 II
Sony A7R III« Full Frame 42.2 7952 53044K/30p26.014.73523100Sony A7R III
Canon 80D« » APS-C 24.0 6000 40001080/60p23.613.2113579Canon 80D
Nikon D7200« » APS-C 24.0 6000 40001080/60p24.514.6133387Nikon D7200
Panasonic GX8« » Four Thirds 20.2 5184 38884K/30p23.512.680675Panasonic GX8
Pentax KP« » APS-C 24.1 6016 40001080/60i----Pentax KP
Pentax K-70« » APS-C 24.0 6000 40001080/60i----Pentax K-70
Pentax K-3« » APS-C 24.1 6016 40001080/60i23.713.4121680Pentax K-3
Pentax K-5« » APS-C 16.1 4928 32641080/25p23.714.1116282Pentax K-5
Sony A7 III« » Full Frame 24.0 6000 40004K/30p25.014.7373096Sony A7 III
Sony A9« » Full Frame 24.0 6000 40004K/30p24.913.3351792Sony A9
Sony A99 II« » Full Frame 42.2 7952 53044K/30p25.413.4231792Sony A99 II
Sony A6300« » APS-C 24.0 6000 40004K/30p24.413.7143785Sony A6300
Sony A6500« » APS-C 24.0 6000 40004K/30p24.513.7140585Sony A6500
Sony A7R II« » Full Frame 42.2 7952 53044K/30p26.013.9343498Sony A7R II
Sony A7S II« » Full Frame 12.0 4240 28324K/30p23.613.3299385Sony A7S II
Sony RX10 II« » 1-inch 20.0 5472 36484K/30p23.012.653170Sony RX10 II

Many modern cameras are not only capable of taking still images, but also of capturing video footage. Both cameras under consideration are equipped with sensors that have a sufficiently high read-out speed for moving images, but the A7R III provides a better video resolution than the K-3 II. It can shoot movie footage at 4K/30p, while the Pentax is limited to 1080/60i.

 

Feature comparison: Pentax K-3 II vs Sony A7R III

Apart from body and sensor, cameras can and do differ across a variety of features. For example, the A7R III has an electronic viewfinder (3686k dots), while the K-3 II 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 following table reports on some other key feature differences and similarities of the Pentax K-3 II, the Sony A7R III, and comparable cameras. The full specs-sheets can be found in the camera manual or in the dpreview camera hub.

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)
Shutter
speed
(1/sec)
Shutter
flaps
(1/sec)
Build-in
Flash
(yes/no)
Build-in
Image
Stab
Camera
Model
Pentax K-3 II»optical Y 3.2 1037 fixed n 8000 8.3 n Y Pentax K-3 II
Sony A7R III«3686 n 3.0 1440 tilting Y 8000 10.0 n Y Sony A7R III
Canon 80D« »optical Y 3.0 1040 swivel Y 8000 7.0 Y n Canon 80D
Nikon D7200« »optical Y 3.2 1229 fixed n 8000 6.0 Y n Nikon D7200
Panasonic GX8« »2360 n 3.0 1040 swivel Y 8000 10.0 n Y Panasonic GX8
Pentax KP« »optical n 3.0 921 tilting n 6000 7.0 Y Y Pentax KP
Pentax K-70« »optical n 3.0 921 swivel n 6000 6.0 Y Y Pentax K-70
Pentax K-3« »optical Y 3.2 1037 fixed n 8000 8.3 Y Y Pentax K-3
Pentax K-5« »optical Y 3.0 921 fixed n 8000 7.0 Y Y Pentax K-5
Sony A7 III« »2359 n 3.0 922 tilting Y 8000 10.0 n Y Sony A7 III
Sony A9« »3686 n 3.0 1440 tilting Y 8000 20.0 n Y Sony A9
Sony A99 II« »2400 Y 3.0 1229 full-flex n 8000 12.0 n Y Sony A99 II
Sony A6300« »2300 n 3.0 922 tilting n 4000 11.0 Y n Sony A6300
Sony A6500« »2300 n 3.0 922 tilting Y 4000 11.0 Y Y Sony A6500
Sony A7R II« »2400 n 3.0 1229 tilting n 8000 5.0 n Y Sony A7R II
Sony A7S II« »2400 n 3.0 1229 tilting n 8000 5.0 n Y Sony A7S II
Sony RX10 II« »2359 Y 3.0 1229 tilting n 3200 14.0 Y Y Sony RX10 II

One feature that is present on the K-3 II, but is missing on the A7R III is a top-level LCD. While being, of course, smaller than the rear screen, the control panel conveys some of the essential shooting information and can be convenient for quick and easy settings verification.

The reported shutter speed and shutter burst refer to the use of the mechanical shutter. In addition, the A7R III features an electronic shutter, which makes completely silent shooting possible. However, this mode is less suitable for photographing moving objects (rolling shutter) or shooting under artificial light sources (flickering).

The K-3 II writes its imaging data to SDXC cards, while the A7R 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.

Input-Output Connections
  Camera
Model
Hotshoe
Port
Internal
Microphone
Internal
Speaker
Microphone
Port
Headphone
Port
HDMI
Port
USB
Type
WiFi
Support
NFC
Support
Bluetooth
Support
Camera
Model
Pentax K-3 II»YmonomonoYYmini3.0---Pentax K-3 II
Sony A7R III«YstereomonoYYmicro3.1YYYSony A7R III
Canon 80D« »YstereomonoYYmini2.0YY-Canon 80D
Nikon D7200« »YstereomonoYYmini2.0YY-Nikon D7200
Panasonic GX8« »YstereomonoY-micro2.0YY-Panasonic GX8
Pentax KP« »YstereomonoY--2.0Y--Pentax KP
Pentax K-70« »YstereomonoY-mini2.0Y--Pentax K-70
Pentax K-3« »YmonomonoYYmini3.0---Pentax K-3
Pentax K-5« »YstereomonoY-mini2.0---Pentax K-5
Sony A7 III« »YstereomonoYYmicro3.1YYYSony A7 III
Sony A9« »YstereomonoYYmicro2.0YYYSony A9
Sony A99 II« »YstereomonoYYmicro2.0YYYSony A99 II
Sony A6300« »YstereomonoY-micro2.0YY-Sony A6300
Sony A6500« »YstereomonoY-micro2.0YY-Sony A6500
Sony A7R II« »YstereomonoYYmicro2.0YY-Sony A7R II
Sony A7S II« »YstereomonoYYmicro2.0YY-Sony A7S II
Sony RX10 II« »YstereomonoYYmicro2.0YY-Sony RX10 II

Both the K-3 II and the A7R III are current models that good online retailers will have in stock. You can check the latest prices, for example, at amazon. The K-3 II replaced the earlier Pentax K-3, while the A7R III followed on from the Sony A7R II.

Review summary: Pentax K-3 II vs Sony A7R III

So how do things add up? Is the Pentax K-3 II better than the Sony A7R III or vice versa? The listing below highlights the relative strengths of the two models.

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Reasons to prefer the Pentax K-3 II:

  • 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.
  • Longer lasting: Can take more shots (720 versus 650) on a single battery charge.
  • More affordable: Was introduced into a lower priced category (66 percent cheaper at launch).
  • More heavily discounted: Has been available for much longer (launched in April 2015).

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Arguments in favor of the Sony Alpha A7R III:

  • More detail: Has more megapixels (42.2 vs 24.1MP), which boosts linear resolution by 32%.
  • Better image quality: Scores substantially higher (20 points) in the DXO overall evaluation.
  • Richer colors: Generates noticeably more natural colors (2.4 bits more color depth).
  • More dynamic range: Captures a broader range of light and dark details (1.1 EV of extra DR).
  • Better low-light sensitivity: Can shoot in dim conditions (1.7 stops ISO advantage).
  • Better video: Provides higher definition movie capture (4K/30p vs 1080/60i).
  • More framing info: Has an electronic viewfinder that displays shooting data.
  • More detailed LCD: Has a higher resolution rear screen (1440k vs 1037k dots).
  • 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.
  • More legacy lens friendly: Can use many non-native lenses via adapters.
  • Faster data transfer: Supports a more advanced USB protocol (3.1 vs 3.0).
  • Easier file upload: Has wifi build 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.
  • More modern: Reflects 2 years and 6 months of technical progress since the K-3 II launch.

If the count of relative strengths (bullet points above) is taken as a measure, the A7R III is the clear winner of the contest (19 : 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.

K-3 II 06:19 A7R III

In any case, while the specs-based evaluation of cameras is instructive in revealing their potential as photographic tools, it remains incomplete and does no justice, for example, to the way the K-3 II or the A7R III handle or perform in practice. 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 summarizes the assessments of some of the best known camera review sites (cameralabs, dpreview, ephotozine, imaging-resource, photographyblog). The detailed reviews can be accessed by clicking on the site logo in the table header.

Review Scores
  Camera
Model
cameralabs dpreview ephotozine imaging-resource photographyblog Camera
Launch
(announced)
Launch
Price
(USD)
Street
Price
(USD)
Used
Price
(USD)
Camera
Model
Pentax K-3 II»--5/54.5/55/5 Apr 2015 1,099 i i Pentax K-3 II
Sony A7R III«HiRec90/1004.5/55/55/5 Oct 2017 3,199 i i Sony A7R III
Canon 80D« »HiRec84/1004.5/54.5/54.5/5 Feb 2016 1,199 i i Canon 80D
Nikon D7200« »HiRec84/1004.5/54/54.5/5 Mar 2015 1,199- i Nikon D7200
Panasonic GX8« »Rec82/1004.5/55/54.5/5 Jul 2015 1,199- i Panasonic GX8
Pentax KP« »-82/1005/5-4.5/5 Jan 2017 1,099 i i Pentax KP
Pentax K-70« »-79/1004.5/54/54.5/5 Jun 2016 649 i i Pentax K-70
Pentax K-3« »-83/1005/54.5/55/5 Oct 2013 1,299- i Pentax K-3
Pentax K-5« »-83/1005/54.5/54.5/5 Sep 2010 1,099- i Pentax K-5
Sony A7 III« »HiRec89/1005/55/55/5 Feb 2018 1,999 i i Sony A7 III
Sony A9« »HiRec89/1005/55/55/5 Apr 2017 4,499 i i Sony A9
Sony A99 II« »-85/1004.5/54.5/54.5/5 Sep 2016 3,199 i i Sony A99 II
Sony A6300« »Rec85/1005/55/55/5 Feb 2016 999- i Sony A6300
Sony A6500« »HiRec85/1004.5/55/54.5/5 Oct 2016 1,399 i i Sony A6500
Sony A7R II« »HiRec90/1005/54.5/55/5 Jun 2015 3,199- i Sony A7R II
Sony A7S II« »Rec-4.5/55/55/5 Sep 2015 2,999 i i Sony A7S II
Sony RX10 II« »HiRec82/1004.5/54.5/54/5 Jun 2015 1,299- i Sony RX10 II

Care should be taken when interpreting the review scores above, 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 comparisons of ratings among very different cameras or across long time periods have little meaning. Also, kindly note that some of the listed sites have over time developped their review approaches and their reporting style.

 

Other camera comparisons

Did this review help to inform your camera decision process? If you would like to see a different side-by-side camera review, just use the search menu below. Alternatively, you can follow any of the listed hyperlinks for comparisons that others found interesting. If the camera you are interested in is not available, please contact me, and I will try to locate and add the respective data to the application.

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