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Pentax 645Z versus Sony A7S II

The Pentax 645Z and the Sony Alpha 7S II are two professional cameras that were announced, respectively, in April 2014 and September 2015. The 645Z is a DSLR, while the A7S II is a mirrorless interchangeable lens camera. The cameras are based on a medium format (645Z) and a full frame sensor. The Pentax has a resolution of 51.1 megapixel, whereas the Sony provides 12 MP.

Body comparison

The physical size and weight of the Pentax 645Z and the Sony A7S II are illustrated in the side-by-side display below. 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. 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 – the 645Z – represents 100 percent across all the size and weight measures).

Pentax 645Z vs Sony A7S II front
645Z versus A7S II top view
645Z and A7S II rear side
Body view (645Z 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 A7S II is notably smaller (33 percent) than the Pentax 645Z. Moreover, the A7S II is substantially lighter (60 percent) than the 645Z. 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 645Z (⇒ rgt) 156 mm 117 mm 123 mm 1550 g 650 YES 2014 8,499 latest check
Sony A7S II (⇒ lft) 127 mm 96 mm 60 mm 627 g 370 YES 2015 2,999 latest check
Canon 5DS R (⇒ lft | rgt) 152 mm 116 mm 76 mm 930 g 700 YES 2015 3,699 latest check
Canon 5DS (⇒ lft | rgt) 152 mm 116 mm 76 mm 930 g 700 YES 2015 3,699 latest check
Hasselblad X1D (⇒ lft | rgt) 150 mm 98 mm 71 mm 725 g .. YES 2016 8,995 latest check
Leica SL (⇒ lft | rgt) 147 mm 104 mm 39 mm 847 g 400 YES 2015 7,450 latest check
Nikon D750 (⇒ lft | rgt) 141 mm 113 mm 78 mm 750 g 1230 YES 2014 2,299 latest check
Nikon D810 (⇒ lft | rgt) 146 mm 123 mm 82 mm 980 g 1200 YES 2014 3,299discont. check
Nikon D4S (⇒ lft | rgt) 160 mm 157 mm 91 mm 1350 g 3020 YES 2014 6,499discont. check
Olympus E-M1 II (⇒ lft | rgt) 134 mm 91 mm 67 mm 574 g 440 YES 2016 1,999 latest check
Pentax 645D (⇒ lft | rgt) 156 mm 117 mm 119 mm 1480 g .. YES 2010 9,995discont. check
Sony A99 II (⇒ lft | rgt) 143 mm 104 mm 76 mm 849 g 490 YES 2016 3,199 latest check
Sony A7R II (⇒ lft | rgt) 127 mm 96 mm 60 mm 625 g 290 YES 2015 3,199discont. check
Sony RX1R II (⇒ lft | rgt) 113 mm 65 mm 72 mm 507 g 220 no 2015 3,299 latest 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

The listed prices provide an indication of the market segment that the manufacturer of the cameras have been targeting. The A7S II was launched at a markedly lower price (by 65 percent) than the 645Z, 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 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 tent to lead to bigger and heavier cameras and lenses.

Of the two cameras under consideration, the Pentax 645Z features a medium format sensor and the Sony A7S II a full frame sensor. The sensor area in the A7S II is 41 percent smaller. As a result of these sensor size differences, the cameras have a format factor of, respectively, 0.79 and 1.0. The sensor in the 645Z has a native 4:3 aspect ratio, while the one in the A7S II offers a 3:2 aspect.

Pentax 645Z and Sony A7S II sensor measures
Sensor size

With 51.1MP, the 645Z offers a higher resolution than the A7S II (12MP), but the 645Z has smaller individual pixels (pixel pitch of 5.30μm versus 8.40μm for the A7S II). Moreover, the A7S II is a somewhat more recent model (by 1 year and 4 months) than the 645Z, and its sensor might have benefitted from technological advances during this time that further enhance the light gathering capacity of its pixels. Coming back to sensor resolution, it should be mentioned that the 645Z has no anti-alias filter installed, so that it can capture all the detail its sensor resolves.

645Z versus A7S II MP
Sensor resolution

For most cameras, data on sensor performance has been reported by DXO Mark. 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"). Of the two cameras under review, the 645Z provides substantially higher image quality than the A7S II, with an overall score that is 16 points higher. This advantage is based on 2.4 bits higher color depth, 1.4 EV in additional dynamic range, and 0.6 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.

Sensor Characteristics
Camera Sensor
Class
Resolution
(Megapixel)
Horiz.
Pixels
Vert.
Pixels
Video
Format
DXO
Portrait
DXO
Landscape
DXO
Sports
DXO
Overall
Pentax 645Z (⇒ rgt) Medium Format 51.1 8256 6192 1080/60i 26.0 14.7 4505 101
Sony A7S II (⇒ lft) Full Frame 12.0 4240 2832 4K/30p 23.6 13.3 2993 85
Canon 5DS R (⇒ lft | rgt) Full Frame 50.3 8688 5792 1080/60p 24.6 12.4 2308 86
Canon 5DS (⇒ lft | rgt) Full Frame 50.3 8688 5792 1080/60p 24.7 12.4 2381 87
Hasselblad X1D (⇒ lft | rgt) Medium Format 51.3 8272 6200 1080/25p 26.2 14.8 4489 102
Leica SL (⇒ lft | rgt) Full Frame 24.0 6000 4000 4K/30p 25.0 13.4 1821 88
Nikon D750 (⇒ lft | rgt) Full Frame 24.2 6016 4016 1080/60p 24.8 14.5 2956 93
Nikon D810 (⇒ lft | rgt) Full Frame 36.2 7360 4912 1080/60p 25.7 14.8 2853 97
Nikon D4S (⇒ lft | rgt) Full Frame 16.2 4928 3280 1080/60p 24.4 13.3 3074 89
Olympus E-M1 II (⇒ lft | rgt) Four Thirds 20.2 5184 3888 4K/30p 23.7 12.8 1312 80
Pentax 645D (⇒ lft | rgt) Medium Format 39.5 7264 5440 no 24.6 12.6 1262 82
Sony A99 II (⇒ lft | rgt) Full Frame 42.2 7952 5304 4K/30p 25.4 13.4 2317 92
Sony A7R II (⇒ lft | rgt) Full Frame 42.2 7952 5304 4K/30p 26.0 13.9 3434 98
Sony RX1R II (⇒ lft | rgt) Full Frame 42.2 7952 5304 1080/60p 25.8 13.9 3204 97
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

Many modern cameras are not only capable of taking still images, but can also record movies. The two cameras under consideration both have sensors whose read-out speed is fast enough to capture moving pictures, but the A7S II provides a better video resolution than the 645Z. It can shoot movie footage at 4K/30p, while the Pentax is limited to 1080/60i.

Feature comparison

Beyond body and sensor, cameras can and do differ across a range of features. For example, the A7S II has an electronic viewfinder (2400k dots), while the 645Z 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 adjacent table lists some of the other core features of the Pentax 645Z and Sony A7S II along with similar information for a selection of comparators. 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 645Z (⇒ rgt) optical YES 3.2 1037 tilting no 4000 3.0 no no
Sony A7S II (⇒ lft) 2400 no 3.0 1229 tilting no 8000 5.0 no YES
Canon 5DS R (⇒ lft | rgt) optical YES 3.2 1040 fixed no 8000 5.0 no no
Canon 5DS (⇒ lft | rgt) optical YES 3.2 1040 fixed no 8000 5.0 no no
Hasselblad X1D (⇒ lft | rgt) 2360 no 3.0 920 fixed YES 2000 2.3 no no
Leica SL (⇒ lft | rgt) 4400 YES 3.0 1040 fixed YES 8000 11.0 no no
Nikon D750 (⇒ lft | rgt) optical YES 3.2 1229 tilting no 4000 6.0 12 no
Nikon D810 (⇒ lft | rgt) optical YES 3.2 1229 fixed no 4000 5.0 12 no
Nikon D4S (⇒ lft | rgt) optical YES 3.2 921 fixed no 8000 11.0 no no
Olympus E-M1 II (⇒ lft | rgt) 2360 no 3.0 1037 swivel YES 8000 18.0 no YES
Pentax 645D (⇒ lft | rgt) optical YES 3.0 921 fixed no 4000 1.1 no no
Sony A99 II (⇒ lft | rgt) 2400 YES 3.0 1229 tilting no 8000 12.0 no YES
Sony A7R II (⇒ lft | rgt) 2400 no 3.0 1229 tilting no 8000 5.0 no YES
Sony RX1R II (⇒ lft | rgt) 2360 no 3.0 1229 tilting no 4000 5.0 no no
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

Both the 645Z and the A7S II are current models that good online retailers will have in stock. You can check the latest prices, for example, at amazon. The 645Z replaced the earlier Pentax 645D, while the A7S II followed on from the Sony A7S.

Summary

So what is the bottom line? Which of the two cameras – the Pentax 645Z or the Sony A7S II – has the upper hand? The listing below highlights the relative strengths of the two models.


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Arguments in favor of the Pentax 645Z:

  • More detail: Offers more megapixels (51.1 vs 12MP) with a 102% higher linear resolution.
  • Maximized detail: Lacks an anti-alias filter to exploit the sensor's full resolution potential.
  • Better image quality: Scores substantially higher (16 points) in the DXO overall assessment.
  • Richer colors: Generates images with noticeably better colors (2.4 bits more color depth).
  • More dynamic range: Captures a larger spectrum of light and dark details (1.4 EV of extra DR).
  • Better low-light sensitivity: Requires less light for good images (0.6 stops ISO advantage).
  • 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.
  • Longer lasting: Can take more shots (650 versus 370) on a single battery charge.
  • More heavily discounted: Has been on the market for longer (launched in April 2014).

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Advantages of the Sony Alpha 7S II:

  • Better moiré control: Has an anti-alias filter to avoid artificial patterns to appear in images.
  • 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 (1229k vs 1037k dots).
  • Faster shutter: Has higher mechanical shutter speed (8000/sec vs 4000/sec) to freeze action.
  • Faster burst: Shoots at higher frequency (5 vs 3 flaps/sec) to capture the decisive moment.
  • More compact: Is smaller (127x96mm vs 156x117mm) and will fit more readily into a bag.
  • Less heavy: Has a lower weight (by 923g or 60 percent) and is thus easier to take along.
  • More legacy lens friendly: Can use many non-native lenses via adapters.
  • Sharper images: Has stabilization technology build-in to reduce the impact of hand-shake.
  • More affordable: Was introduced into a lower priced category (65 percent cheaper at launch).
  • More modern: Was introduced somewhat (1 year and 4 months) more recently.

If the number of relative strengths (bullet points above) is taken as a guide, the A7S II comes out slightly ahead of the 645Z (12 : 11 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.

645Z 11:12 A7S II

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 645Z or the A7S II handle or perform in practice. User reviews, such as those found at amazon, can sometimes inform about these issues, but such feedback is often incomplete, inconsistent, and biased. This is where reviews by experts come in. The following table reports the overall rankings of the cameras as published by some of the major camera review sites. The detailed reviews can be accessed, respectively, on the websites of 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 645Z (⇒ rgt) - - 4.5/5 5/5 5/5 2014 8,499 latest check
Sony A7S II (⇒ lft) Rec - 4.5/5 5/5 5/5 2015 2,999 latest check
Canon 5DS R (⇒ lft | rgt) Rec 83/100 Silver 5/5 5/5 4.5/5 2015 3,699 latest check
Canon 5DS (⇒ lft | rgt) Rec 83/100 Silver 4.5/5 5/5 4.5/5 2015 3,699 latest check
Hasselblad X1D (⇒ lft | rgt) - - - - 4/5 2016 8,995 latest check
Leica SL (⇒ lft | rgt) - 84/100 4.5/5 4/5 4/5 2015 7,450 latest check
Nikon D750 (⇒ lft | rgt) HiRec 90/100 Gold 4.5/5 5/5 4.5/5 2014 2,299 latest check
Nikon D810 (⇒ lft | rgt) - 86/100 Gold 5/5 4.5/5 4.5/5 2014 3,299discont. check
Nikon D4S (⇒ lft | rgt) - - 4.5/5 5/5 4.5/5 2014 6,499discont. check
Olympus E-M1 II (⇒ lft | rgt) HiRec 85/100 Gold 4.5/5 5/5 4.5/5 2016 1,999 latest check
Pentax 645D (⇒ lft | rgt) - - - 4.5/5 - 2010 9,995discont. check
Sony A99 II (⇒ lft | rgt) - 85/100 Silver 4.5/5 4.5/5 4.5/5 2016 3,199 latest check
Sony A7R II (⇒ lft | rgt) HiRec 90/100 Gold 5/5 4.5/5 5/5 2015 3,199discont. check
Sony RX1R II (⇒ lft | rgt) - 82/100 Silver - reviewed 4.5/5 2015 3,299 latest 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

Care should be taken when interpreting the review scores above, though. The ratings are only valid when refering to cameras in the same category and of the same age. 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, kindly note that some of the listed sites have over time developped their review approaches and their reporting style.

Other comparisons

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. If the camera you are interested in is not available, kindly get in touch, and I will try to update the database with the necessary infos.

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