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Pentax K-3 II versus Sony A7

The Pentax K-3 II and the Sony Alpha A7 are two enthusiast cameras that were announced, respectively, in April 2015 and October 2013. The K-3 II is a DSLR, while the A7 is a mirrorless interchangeable lens camera. The cameras are based on an APS-C (K-3 II) and a full frame sensor. The Pentax has a resolution of 24.1 megapixel, whereas the Sony provides 24 MP.

Body comparison

An illustration of the physical size and weight of the Pentax K-3 II and the Sony A7 is provided in the side-by-side display below. Three successive views from the front, the top, and the rear are shown. All size dimensions are rounded to the nearest millimeter. You can also toggle the display 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).

Pentax K-3 II vs Sony A7 front
K-3 II versus A7 top view
K-3 II and A7 rear side
Body view (K-3 II on the left)

If the front view area (width x height) of the cameras is taken as an aggregate measure of their size, the Sony A7 is somewhat smaller (9 percent) than the Pentax K-3 II. Moreover, the A7 is substantially lighter (41 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.

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, just select a new right or left comparator from among the camera models in the table. Alternatively, you can also move across to the CAM-parator tool and choose from the broad selection of possible comparisons there.

Camera Body Specifications
Camera Camera
Width
Camera
Height
Camera
Depth
Camera
Weight
Battery
Life
(CIPA)
Weather
Sealing
(y/n)
Camera
Launch
(year)
Launch
Price
(USD)
Street
Price
(amazon)
Used
Price
(ebay)
Pentax K-3 II (⇒ rgt) 131 mm 100 mm 77 mm 800 g 720 YES 2015 1,099 latest check
Sony A7 (⇒ lft) 127 mm 94 mm 48 mm 474 g 340 YES 2013 1,699discont. check
Canon 80D (⇒ lft | rgt) 139 mm 105 mm 79 mm 730 g 960 YES 2016 1,199 latest check
Nikon D7200 (⇒ lft | rgt) 136 mm 107 mm 76 mm 765 g 1110 YES 2015 1,199discont. check
Nikon D610 (⇒ lft | rgt) 141 mm 113 mm 82 mm 850 g 900 YES 2013 1,999 latest check
Olympus E-M1 II (⇒ lft | rgt) 134 mm 91 mm 67 mm 574 g 440 YES 2016 1,999 latest check
Olympus PEN-F (⇒ lft | rgt) 125 mm 72 mm 37 mm 427 g 330 no 2016 1,199 latest check
Olympus E-M5 II (⇒ lft | rgt) 124 mm 85 mm 45 mm 469 g 310 YES 2015 1,099 latest check
Panasonic GX8 (⇒ lft | rgt) 133 mm 78 mm 63 mm 487 g 330 YES 2015 1,199 latest check
Panasonic GH4 (⇒ lft | rgt) 133 mm 93 mm 84 mm 560 g 500 YES 2014 1,499discont. check
Pentax KP (⇒ lft | rgt) 132 mm 101 mm 76 mm 703 g 390 YES 2017 1,099 latest check
Pentax K-70 (⇒ lft | rgt) 126 mm 93 mm 74 mm 688 g 410 YES 2016 649 latest check
Pentax K-3 (⇒ lft | rgt) 131 mm 100 mm 77 mm 800 g 560 YES 2013 1,299discont. check
Sony RX10 II (⇒ lft | rgt) 129 mm 88 mm 102 mm 813 g 400 YES 2015 1,299discont. check
Sony A7 II (⇒ lft | rgt) 127 mm 96 mm 60 mm 599 g 350 YES 2014 1,999 latest check
Sony A7S (⇒ lft | rgt) 127 mm 94 mm 48 mm 489 g 380 YES 2014 2,499discont. check
Sony A7R (⇒ lft | rgt) 127 mm 94 mm 48 mm 465 g 340 YES 2013 2,299discont. check

The listed prices provide an indication of the market segment that the manufacturer of the cameras have been targeting. The K-3 II was launched at a markedly lower price (by 35 percent) than the A7, 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. Then, after the new model is out, very good deals can frequently be found on the pre-owned market.

Sensor comparison

The size of the sensor inside a digital camera is one of the key determinants 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. Further, a large sensor camera will give the photographer additional creative options when using shallow depth-of-field to isolate a subject from its 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 A7 a full frame sensor. The sensor area in the A7 is 133 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 A7 sensor measures
Sensor size

Despite having a smaller sensor, the Pentax K-3 II offers a higher resolution of 24.1 megapixel, compared with 24 MP of the Sony A7. This megapixel 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 5.97μm for the A7). However, it should be noted that the K-3 II is a somewhat more recent model (by 1 year and 6 months) than the A7, and its sensor might have benefitted from technological advances during this time that partly offset its pixel-size disadvantage. Coming back to sensor resolution, it should be mentioned that the K-3 II has no anti-alias filter installed, so that it can capture all the detail its sensor resolves.

Unlike the A7, the K-3 II has the capacity to capture high quality composite images 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).

K-3 II versus A7 MP
Sensor resolution

Since 2007, DXO Mark has published sensor performance measurements that have been derived using a consistent methodology. This service is based on lab testing and assigns an overall score to each camera sensor, as well as ratings for dynamic range ("DXO Landscape"), color depth ("DXO Portrait"), and low-light sensitivity ("DXO Sports"). Of the two cameras under consideration, the A7 has a markedly higher DXO score than the K-3 II (overall score 10 points higher), which will translate into better image quality. The advantage is based on 1.2 bits higher color depth, 0.6 EV in additional dynamic range, and 1 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 Sensor
Class
Resolution
(Megapixel)
Horiz.
Pixels
Vert.
Pixels
Video
Format
DXO
Portrait
DXO
Landscape
DXO
Sports
DXO
Overall
Pentax K-3 II (⇒ rgt) APS-C 24.1 6016 4000 1080/60i 23.6 13.6 1106 80
Sony A7 (⇒ lft) Full Frame 24.0 6000 4000 1080/60p 24.8 14.2 2248 90
Canon 80D (⇒ lft | rgt) APS-C 24.0 6000 4000 1080/60p 23.6 13.2 1135 79
Nikon D7200 (⇒ lft | rgt) APS-C 24.0 6000 4000 1080/60p 24.5 14.6 1333 87
Nikon D610 (⇒ lft | rgt) Full Frame 24.2 6016 4016 1080/30p 25.1 14.4 2925 94
Olympus E-M1 II (⇒ lft | rgt) Four Thirds 20.2 5184 3888 4K/30p 23.7 12.8 1312 80
Olympus PEN-F (⇒ lft | rgt) Four Thirds 20.2 5184 3888 1080/60p 23.1 12.4 894 74
Olympus E-M5 II (⇒ lft | rgt) Four Thirds 15.9 4608 3456 1080/60p 23.0 12.5 842 73
Panasonic GX8 (⇒ lft | rgt) Four Thirds 20.2 5184 3888 4K/30p 23.5 12.6 806 75
Panasonic GH4 (⇒ lft | rgt) Four Thirds 15.9 4608 3456 4K/30p 23.2 12.8 791 74
Pentax KP (⇒ lft | rgt) APS-C 24.1 6016 4000 1080/60i - - - -
Pentax K-70 (⇒ lft | rgt) APS-C 24.0 6000 4000 1080/60i - - - -
Pentax K-3 (⇒ lft | rgt) APS-C 24.1 6016 4000 1080/60i 23.7 13.4 1216 80
Sony RX10 II (⇒ lft | rgt) 1-inch 20.0 5472 3648 4K/30p 23.0 12.6 531 70
Sony A7 II (⇒ lft | rgt) Full Frame 24.0 6000 4000 1080/60p 24.9 13.6 2449 90
Sony A7S (⇒ lft | rgt) Full Frame 12.0 4240 2832 1080/60p 23.9 13.2 3702 87
Sony A7R (⇒ lft | rgt) Full Frame 36.2 7360 4912 1080/60p 25.6 14.1 2746 95

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 provides a faster frame rate than the K-3 II. It can shoot movie footage at 1080/60p, while the Pentax is limited to 1080/60i.

Feature comparison

Apart from body and sensor, cameras can and do differ across a range of features. For example, the A7 has an electronic viewfinder (2400k 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 table below summarizes some of the other core capabilities of the Pentax K-3 II and Sony A7 in connection with corresponding information for a sample of similar cameras. The full specs-sheets can be found in the camera manual or, for example, in the dpreview camera hub.

Core Features
Camera Viewfinder
(Type or
'000 dots)
Control
Panel
(Y/n)
LCD
Size
(inch)
LCD
Resolution
('000 dots)
LCD
Attach-
ment
Touch
Screen
(Y/n)
Shutter
speed
(1/sec)
Shutter
flaps
(1/sec))
Build-in
Flash
(GN)
Build-in
Image
Stab
Pentax K-3 II (⇒ rgt) optical YES 3.2 1037 fixed no 8000 8.3 no YES
Sony A7 (⇒ lft) 2400 no 3.0 1230 tilting no 8000 5.0 no no
Canon 80D (⇒ lft | rgt) optical YES 3.0 1040 swivel YES 8000 7.0 12 no
Nikon D7200 (⇒ lft | rgt) optical YES 3.2 1229 fixed no 8000 6.0 12 no
Nikon D610 (⇒ lft | rgt) optical YES 3.2 921 fixed no 4000 6.0 12 no
Olympus E-M1 II (⇒ lft | rgt) 2360 no 3.0 1037 swivel YES 8000 18.0 no YES
Olympus PEN-F (⇒ lft | rgt) 2360 no 3.0 1037 swivel YES 8000 10.0 no YES
Olympus E-M5 II (⇒ lft | rgt) 2360 no 3.0 1037 swivel YES 8000 10.0 no YES
Panasonic GX8 (⇒ lft | rgt) 2360 no 3.0 1040 swivel YES 8000 10.0 no YES
Panasonic GH4 (⇒ lft | rgt) 2359 no 3.0 1036 swivel YES 8000 12.0 17 no
Pentax KP (⇒ lft | rgt) optical no 3.0 921 tilting no 6000 7.0 YES YES
Pentax K-70 (⇒ lft | rgt) optical no 3.0 921 swivel no 6000 6.0 YES YES
Pentax K-3 (⇒ lft | rgt) optical YES 3.2 1037 fixed no 8000 8.3 13 YES
Sony RX10 II (⇒ lft | rgt) 2359 YES 3.0 1229 tilting no 3200 14.0 10.2 YES
Sony A7 II (⇒ lft | rgt) 2400 no 3.0 1230 tilting no 8000 5.0 no YES
Sony A7S (⇒ lft | rgt) 2400 no 3.0 921 tilting no 8000 5.0 no no
Sony A7R (⇒ lft | rgt) 2400 no 3.0 1230 tilting no 8000 4.0 no no

The K-3 II is a current model that online retailers, such as amazon, will have in stock. In contrast, the A7 has been discontinued (but it can be found pre-owned on ebay). As a replacement in the same line of cameras, the A7 was succeeded by the Sony A7 II.

Summary

So how do things add up? Is the Pentax K-3 II better than the Sony A7 or vice versa? The listing below highlights the relative strengths of the two models.


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Advantages of the Pentax K-3 II:

  • Maximized detail: Lacks an anti-alias filter to exploit the sensor's full resolution potential.
  • High quality composites: Can combine several shots after pixel-shifting its sensor.
  • Brighter framing: Features an optical viewfinder for clear, lag-free composition.
  • Easier setting verification: Has 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.
  • Faster burst: Shoots at higher frequency (8.3 vs 5 flaps/sec) to capture the decisive moment.
  • Longer lasting: Can take more shots (720 versus 340) on a single battery charge.
  • Sharper images: Has hand-shake reducing image stabilization build-in.
  • More affordable: Was introduced into a lower priced category (35 percent cheaper at launch).
  • More modern: Is somewhat more recent (announced 1 year and 6 months after the A7).

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Reasons to prefer the Sony Alpha A7:

  • Better moiré control: Has an anti-alias filter to avoid artificial patterns to appear in images.
  • Better image quality: Scores markedly higher (10 points) in the DXO overall evaluation.
  • Richer colors: Generates noticeably more natural colors (1.2 bits more color depth).
  • More dynamic range: Captures a broader range of light and dark details (0.6 EV of extra DR).
  • Better low-light sensitivity: Can shoot in dim conditions (1 stops ISO advantage).
  • Better video: Provides higher movie framerates (1080/60p vs 1080/60i).
  • More framing info: Has an electronic viewfinder that displays shooting data.
  • More detailed LCD: Has a higher resolution rear screen (1230k vs 1037k dots).
  • More flexible LCD: Has a tilting screen for odd-angle shots in landscape orientation.
  • Less heavy: Has a lower weight (by 326g or 41 percent) and is thus easier to take along.
  • More legacy lens friendly: Can use many non-native lenses via adapters.
  • More heavily discounted: Has been on the market for longer (launched in October 2013).

If the count of individual advantages (bullet points above) is taken as a guide, the A7 emerges as the winner of the match-up (12 : 10 points). However, the relevance of individual strengths will vary across photographers, so that you might want to apply your own weighing scheme to the summary points.

K-3 II 10:12 A7

In any case, while the specs-based evaluation of cameras is instructive in revealing their potential as photographic tools, it says nothing about, for example, the handling, responsiveness, and overall imaging quality of the K-3 II and the A7 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 expert reviews are important. The table below summarizes the assessments of some of the best known camera review sites. The full reviews are available, respectively, at cameralabs.com, dpreview.com, ephotozine.com, imaging-resource.com, and photographyblog.com.

Review scores
Camera camera
labs
dp
review
ephoto
zine
imaging
resource
photography
blog
Camera
Launch
(year)
Launch
Price
(USD)
Street
Price
(amazon)
Used
Price
(ebay)
Pentax K-3 II (⇒ rgt) - - 5/5 4.5/5 5/5 2015 1,099 latest check
Sony A7 (⇒ lft) HiRec 80/100 Silver 5/5 4.5/5 5/5 2013 1,699discont. check
Canon 80D (⇒ lft | rgt) HiRec 84/100 Silver 4.5/5 4.5/5 4.5/5 2016 1,199 latest check
Nikon D7200 (⇒ lft | rgt) HiRec 84/100 Silver 4.5/5 4/5 4.5/5 2015 1,199discont. check
Nikon D610 (⇒ lft | rgt) HiRec 87/100 Gold 4.5/5 4.5/5 4.5/5 2013 1,999 latest check
Olympus E-M1 II (⇒ lft | rgt) HiRec 85/100 Gold 4.5/5 5/5 4.5/5 2016 1,999 latest check
Olympus PEN-F (⇒ lft | rgt) - 82/100 Silver 4.5/5 4.5/5 5/5 2016 1,199 latest check
Olympus E-M5 II (⇒ lft | rgt) HiRec 81/100 Silver 5/5 4.5/5 5/5 2015 1,099 latest check
Panasonic GX8 (⇒ lft | rgt) Rec 82/100 Silver 4.5/5 5/5 4.5/5 2015 1,199 latest check
Panasonic GH4 (⇒ lft | rgt) HiRec 85/100 Gold 5/5 5/5 5/5 2014 1,499discont. check
Pentax KP (⇒ lft | rgt) - 82/100 Silver 5/5 - 4.5/5 2017 1,099 latest check
Pentax K-70 (⇒ lft | rgt) - 79/100 Silver 4.5/5 4/5 4.5/5 2016 649 latest check
Pentax K-3 (⇒ lft | rgt) - 83/100 Gold 5/5 4.5/5 5/5 2013 1,299discont. check
Sony RX10 II (⇒ lft | rgt) HiRec 82/100 Gold 4.5/5 4.5/5 4/5 2015 1,299discont. check
Sony A7 II (⇒ lft | rgt) Rec 82/100 Silver 4.5/5 5/5 5/5 2014 1,999 latest check
Sony A7S (⇒ lft | rgt) - 86/100 Gold 4.5/5 4.5/5 5/5 2014 2,499discont. check
Sony A7R (⇒ lft | rgt) HiRec 82/100 Gold 4.5/5 5/5 5/5 2013 2,299discont. check

The review scores listed above should be treated with care, 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 comparisons of ratings among very different cameras or across long time periods 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 comparisons

In case you are interested in seeing how other cameras pair up, just make your choice using the following search menu. An an alternative, you can also directly jump to any one of the listed comparisons that were previously generated by the CAM-parator tool. If the camera you are interested in is not available, please send me an email, and I will try to update the database with the necessary infos.

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