Pentax 645Z versus Sony A7R III
The Pentax 645Z and the Sony Alpha A7R III are two digital cameras that were revealed to the public, respectively, in April 2014 and October 2017. The 645Z is a DSLR, while the A7R III 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 42.2 MP.
An illustration of the physical size and weight of the Pentax 645Z and the Sony A7R III is provided in the side-by-side display below. Three consecutive perspectives from the front, the top, and the back are presented. 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 the basis or 100 percent across all the size and weight measures).
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 (33 percent) than the Pentax 645Z. Moreover, the A7R III is substantially lighter (58 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
|Pentax 645Z (⇒ rgt)||156 mm||117 mm||123 mm||1550 g||650||YES||2014||8,499||latest||check|
|Sony A7R III (⇒ lft)||127 mm||96 mm||74 mm||650 g||650||YES||2017||3,199||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||3,299||discont.||check|
|Nikon D4S (⇒ lft | rgt)||160 mm||157 mm||91 mm||1350 g||3020||YES||2014||6,499||discont.||check|
|Nikon D7100 (⇒ lft | rgt)||136 mm||107 mm||76 mm||765 g||950||YES||2013||1,199||discont.||check|
|Nikon D610 (⇒ lft | rgt)||141 mm||113 mm||82 mm||850 g||900||YES||2013||1,999||latest||check|
|Pentax 645D (⇒ lft | rgt)||156 mm||117 mm||119 mm||1480 g||800||YES||2010||9,995||discont.||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||3,199||discont.||check|
|Sony A7S II (⇒ lft | rgt)||127 mm||96 mm||60 mm||627 g||370||YES||2015||2,999||latest||check|
|Sony A7 II (⇒ lft | rgt)||127 mm||96 mm||60 mm||599 g||350||YES||2014||1,999||latest||check|
|Sony A7R (⇒ lft | rgt)||127 mm||94 mm||48 mm||465 g||340||YES||2013||2,299||discont.||check|
The listed prices provide an indication of the market segment that the manufacturer of the cameras have been targeting. The A7R III was launched at a markedly lower price (by 62 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.
The size of the imaging sensor is a crucial determinant of image quality. All other things equal, a large sensor will have larger individual pixel-units that offer better low-light sensitivity, wider dynamic range, and richer color depth than smaller pixels 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 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 A7R III a full frame sensor. The sensor area in the A7R III is 40 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 A7R III offers a 3:2 aspect.
With 51.1MP, the 645Z offers a higher resolution than the A7R III (42.2MP), but the 645Z nevertheless has larger individual pixels (pixel pitch of 5.30μm versus 4.52μm for the A7R III) due to its larger sensor. However, the A7R III is a somewhat more recent model (by 3 years and 6 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 neither of the two cameras has an anti-alias filter installed, so they are able to capture all the detail the sensor resolves.
Unlike the 645Z, the A7R III 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).
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"). The Overall DXO ratings for the two cameras under consideration are close, suggesting that they provide similar image quality. The adjacent table reports on the physical sensor characteristics and the outcomes of the DXO sensor quality tests for a sample of comparator-cameras.
|Pentax 645Z (⇒ rgt)||Medium Format||51.1||8256||6192||1080/60i||26.0||14.7||4505||101|
|Sony A7R III (⇒ lft)||Full Frame||42.2||7952||5304||4K/30p||26.0||14.7||3523||100|
|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|
|Nikon D7100 (⇒ lft | rgt)||APS-C||24.0||6000||4000||1080/60p||24.2||13.7||1256||83|
|Nikon D610 (⇒ lft | rgt)||Full Frame||24.2||6016||4016||1080/30p||25.1||14.4||2925||94|
|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 A7S II (⇒ lft | rgt)||Full Frame||12.0||4240||2832||4K/30p||23.6||13.3||2993||85|
|Sony A7 II (⇒ lft | rgt)||Full Frame||24.0||6000||4000||1080/60p||24.9||13.6||2449||90|
|Sony A7R (⇒ lft | rgt)||Full Frame||36.2||7360||4912||1080/60p||25.6||14.1||2746||95|
Many modern cameras cannot only take still pictures, but also record videos. The two cameras under consideration both have sensors whose read-out speed is fast enough to capture moving pictures, but the A7R III provides a better video resolution than the 645Z. It can shoot movie footage at 4K/30p, while the Pentax is limited to 1080/60i.
Beyond body and sensor, cameras can and do differ across a range of features. For example, the A7R III has an electronic viewfinder (3686k 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 following table reports on some other key feature differences and similarities of the Pentax 645Z, the Sony A7R III, and comparable cameras. If you need more detail on the specs, you can find comprehensive listings, for example, in the dpreview camera hub.
|Pentax 645Z (⇒ rgt)||optical||YES||3.2||1037||tilting||no||4000||3.0||no||no|
|Sony A7R III (⇒ lft)||3686||no||3.0||1440||tilting||YES||8000||10.0||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|
|Nikon D7100 (⇒ 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|
|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 A7S II (⇒ lft | rgt)||2400||no||3.0||1229||tilting||no||8000||5.0||no||YES|
|Sony A7 II (⇒ lft | rgt)||2400||no||3.0||1230||tilting||no||8000||5.0||no||YES|
|Sony A7R (⇒ lft | rgt)||2400||no||3.0||1230||tilting||no||8000||4.0||no||no|
Both the 645Z 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 645Z replaced the earlier Pentax 645D, while the A7R III followed on from the Sony A7R II.
So how do things add up? Is the Pentax 645Z better than the Sony A7R III or vice versa? The listing below highlights the relative strengths of the two models.
Reasons to prefer the Pentax 645Z:
- More detail: Offers more megapixels (51.1 vs 42.2MP) with a 8% higher linear resolution.
- Better low-light sensitivity: Requires less light for good images (0.4 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.
- More heavily discounted: Has been available for much longer (launched in April 2014).
Arguments in favor of the Sony Alpha A7R III:
- High quality composites: Can combine several shots after pixel-shifting its sensor.
- 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).
- Fewer buttons to press: Has a touchscreen to facilitate handling and shooting adjustments.
- Faster shutter: Has higher mechanical shutter speed (8000/sec vs 4000/sec) to freeze action.
- Faster burst: Shoots at higher frequency (10 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 900g or 58 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 (62 percent cheaper at launch).
- More modern: Reflects 3 years and 6 months of technical progress since the 645Z 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 (13 : 6 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.
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 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. The detailed reviews can be accessed, respectively, on the websites of cameralabs.com, dpreview.com, ephotozine.com, imaging-resource.com, and photographyblog.com.
|Pentax 645Z (⇒ rgt)||-||-||4.5/5||5/5||5/5||2014||8,499||latest||check|
|Sony A7R III (⇒ lft)||HiRec||90/100 Gold||4.5/5||5/5||5/5||2017||3,199||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||3,299||discont.||check|
|Nikon D4S (⇒ lft | rgt)||-||-||4.5/5||5/5||4.5/5||2014||6,499||discont.||check|
|Nikon D7100 (⇒ lft | rgt)||HiRec||85/100 Gold||4.5/5||5/5||4.5/5||2013||1,199||discont.||check|
|Nikon D610 (⇒ lft | rgt)||HiRec||87/100 Gold||4.5/5||4.5/5||4.5/5||2013||1,999||latest||check|
|Pentax 645D (⇒ lft | rgt)||-||-||-||4.5/5||-||2010||9,995||discont.||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||3,199||discont.||check|
|Sony A7S II (⇒ lft | rgt)||Rec||-||4.5/5||5/5||5/5||2015||2,999||latest||check|
|Sony A7 II (⇒ lft | rgt)||Rec||82/100 Silver||4.5/5||5/5||5/5||2014||1,999||latest||check|
|Sony A7R (⇒ lft | rgt)||HiRec||82/100 Gold||4.5/5||5/5||5/5||2013||2,299||discont.||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. 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. Also, kindly note that some of the listed sites have over time developped their review approaches and their reporting style.
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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