Pentax 645D versus Sony A7R III
The Pentax 645D and the Sony Alpha A7R III are two digital cameras that were officially introduced, respectively, in March 2010 and October 2017. The 645D is a DSLR, while the A7R III is a mirrorless interchangeable lens camera. The cameras are based on a medium format (645D) and a full frame sensor. The Pentax has a resolution of 39.5 megapixel, whereas the Sony provides 42.2 MP.
The physical size and weight of the Pentax 645D and the Sony A7R III are illustrated in the side-by-side display below. Three consecutive views from the front, the top, and the rear side 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 side – the 645D – represents the basis for the calculations 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 645D. Moreover, the A7R III is substantially lighter (56 percent) than the 645D. 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 645D (⇒ rgt)||156 mm||117 mm||119 mm||1480 g||..||YES||2010||9,995||discont.||check|
|Sony A7R III (⇒ lft)||127 mm||96 mm||74 mm||650 g||650||YES||2017||3,199||latest||check|
|Canon 1D X Mark II (⇒ lft | rgt)||158 mm||168 mm||83 mm||1530 g||1210||YES||2016||5,999||latest||check|
|Canon 1D X (⇒ lft | rgt)||158 mm||168 mm||83 mm||1551 g||1120||YES||2011||6,799||discont.||check|
|Canon 1D Mark IV (⇒ lft | rgt)||156 mm||157 mm||80 mm||1230 g||1500||YES||2009||4,999||discont.||check|
|Leica S Typ 006 (⇒ lft | rgt)||160 mm||120 mm||80 mm||1260 g||..||YES||2012||21,950||discont.||check|
|Nikon D850 (⇒ lft | rgt)||146 mm||124 mm||79 mm||1005 g||1840||YES||2017||3,299||latest||check|
|Nikon D5 (⇒ lft | rgt)||160 mm||159 mm||92 mm||1415 g||3780||YES||2016||6,499||latest||check|
|Nikon D810 (⇒ lft | rgt)||146 mm||123 mm||82 mm||980 g||1200||YES||2014||3,299||discont.||check|
|Nikon D3S (⇒ lft | rgt)||160 mm||157 mm||88 mm||1240 g||4200||YES||2009||5,199||discont.||check|
|Pentax 645Z (⇒ lft | rgt)||156 mm||117 mm||123 mm||1550 g||650||YES||2014||8,499||latest||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 68 percent) than the 645D, 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 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. 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 associated with larger, more expensive camera bodies and lenses.
Of the two cameras under consideration, the Pentax 645D features a medium format sensor and the Sony A7R III a full frame sensor. The sensor area in the A7R III 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 645D has a native 4:3 aspect ratio, while the one in the A7R III offers a 3:2 aspect.
Despite having a smaller sensor, the A7R III offers a slightly higher resolution of 42.2 megapixel, compared with 39.5 MP of the 645D. 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 4.52μm versus 6.06μm for the 645D). However, it should be noted that the A7R III is much more recent (by 7 years and 7 months) than the 645D, and its sensor will have benefitted from technological advances during this time that make it possible to gather light more efficiently. 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 645D, 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).
Since 2007, DXO Mark has published sensor performance measurements that have been derived using a consistent methodology. 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 645D (overall score 18 points higher). The advantage is based on 1.4 bits higher color depth, 2.1 EV in additional dynamic range, and 1.5 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.
|Pentax 645D (⇒ rgt)||Medium Format||39.5||7264||5440||no||24.6||12.6||1262||82|
|Sony A7R III (⇒ lft)||Full Frame||42.2||7952||5304||4K/30p||26.0||14.7||3523||100|
|Canon 1D X Mark II (⇒ lft | rgt)||Full Frame||20.0||5472||3648||4K/60p||24.1||13.5||3207||88|
|Canon 1D X (⇒ lft | rgt)||Full Frame||17.9||5184||3456||1080/30p||23.8||11.8||2786||82|
|Canon 1D Mark IV (⇒ lft | rgt)||APS-H||16.0||4896||3264||1080/30p||22.8||12.0||1320||74|
|Leica S Typ 006 (⇒ lft | rgt)||Medium Format||37.5||7500||5000||no||23.9||12.2||824||76|
|Nikon D850 (⇒ lft | rgt)||Full Frame||45.4||8256||5504||4K/30p||26.4||14.8||2660||100|
|Nikon D5 (⇒ lft | rgt)||Full Frame||20.7||5588||3712||4K/30p||25.1||12.3||2343||88|
|Nikon D810 (⇒ lft | rgt)||Full Frame||36.2||7360||4912||1080/60p||25.7||14.8||2853||97|
|Nikon D3S (⇒ lft | rgt)||Full Frame||12.1||4256||2832||720/24p||23.5||12.0||3253||82|
|Pentax 645Z (⇒ lft | rgt)||Medium Format||51.1||8256||6192||1080/60i||26.0||14.7||4505||101|
|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 are not only capable of taking still images, but can also record movies. The A7R III indeed provides for movie recording, while the 645D does not. The highest resolution format that the A7R III can use is 4K/30p.
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 645D 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 645D, the Sony A7R III, and comparable cameras. If needed, the dpreview camera hub, for example, contains further detail on the cameras' specs.
|Pentax 645D (⇒ rgt)||optical||YES||3.0||921||fixed||no||4000||1.1||no||no|
|Sony A7R III (⇒ lft)||3686||no||3.0||1440||tilting||YES||8000||10.0||no||YES|
|Canon 1D X Mark II (⇒ lft | rgt)||optical||YES||3.2||1620||fixed||YES||8000||16.0||no||no|
|Canon 1D X (⇒ lft | rgt)||optical||YES||3.2||1040||fixed||no||8000||14.0||no||no|
|Canon 1D Mark IV (⇒ lft | rgt)||optical||YES||3.0||920||fixed||no||8000||10.0||no||no|
|Leica S Typ 006 (⇒ lft | rgt)||optical||YES||3.0||922||fixed||no||4000||1.5||no||no|
|Nikon D850 (⇒ lft | rgt)||optical||YES||3.2||2359||tilting||YES||8000||9.0||no||no|
|Nikon D5 (⇒ lft | rgt)||optical||YES||3.2||2359||fixed||YES||8000||14.0||no||no|
|Nikon D810 (⇒ lft | rgt)||optical||YES||3.2||1229||fixed||no||4000||5.0||12||no|
|Nikon D3S (⇒ lft | rgt)||optical||YES||3.0||921||fixed||no||8000||11.0||no||no|
|Pentax 645Z (⇒ lft | rgt)||optical||YES||3.2||1037||tilting||no||4000||3.0||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|
The A7R III is a current model that online retailers, such as amazon, will have in stock. In contrast, the 645D has been discontinued (but it can be found pre-owned on ebay). As a replacement in the same line of cameras, the 645D was succeeded by the Pentax 645Z.
So how do things add up? Is the Pentax 645D better than the Sony A7R III or vice versa? Below is a summary of the relative strengths of each of the two contestants.
Arguments in favor of the Pentax 645D:
- Brighter framing: Features an optical viewfinder for clear, lag-free composition.
- Easier setting verification: Has an LCD display on top to control shooting parameters.
- More heavily discounted: Has been available for much longer (launched in March 2010).
Reasons to prefer the Sony Alpha A7R III:
- More detail: Has more megapixels (42.2 vs 39.5MP), which boosts linear resolution by 5%.
- High quality composites: Can combine several shots after pixel-shifting its sensor.
- Better image quality: Scores substantially higher (18 points) in the DXO overall evaluation.
- Richer colors: Generates noticeably more natural colors (1.4 bits more color depth).
- More dynamic range: Captures a broader range of light and dark details (2.1 EV of extra DR).
- Better low-light sensitivity: Can shoot in dim conditions (1.5 stops ISO advantage).
- Broader imaging potential: Can capture not only stills but also 4K/30p video.
- More framing info: Has an electronic viewfinder that displays shooting data.
- More detailed LCD: Has a higher resolution rear screen (1440k vs 921k 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 shutter: Has higher mechanical shutter speed (8000/sec vs 4000/sec) to freeze action.
- Faster burst: Shoots at higher frequency (10 vs 1.1 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 830g or 56 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 (68 percent cheaper at launch).
- More modern: Reflects 7 years and 7 months of technical progress since the 645D 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 : 3 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 comparison of technical specifications can provide a useful overview of the capabilities of different cameras, it remains partial and cannot reveal, for example, the handling experience and imaging performance when actually working with the 645D or the A7R III. 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 why hands-on reviews by experts 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.
|Pentax 645D (⇒ rgt)||-||-||-||4.5/5||-||2010||9,995||discont.||check|
|Sony A7R III (⇒ lft)||HiRec||90/100 Gold||..||..||..||2017||3,199||latest||check|
|Canon 1D X Mark II (⇒ lft | rgt)||-||89/100 Gold||4.5/5||5/5||4.5/5||2016||5,999||latest||check|
|Canon 1D X (⇒ lft | rgt)||-||-||4.5/5||4.5/5||4.5/5||2011||6,799||discont.||check|
|Canon 1D Mark IV (⇒ lft | rgt)||-||89/100 Gold||-||5/5||-||2009||4,999||discont.||check|
|Leica S Typ 006 (⇒ lft | rgt)||-||-||-||-||-||2012||21,950||discont.||check|
|Nikon D850 (⇒ lft | rgt)||HiRec||89/100 Gold||4.5/5||..||5/5||2017||3,299||latest||check|
|Nikon D5 (⇒ lft | rgt)||-||89/100 Gold||4.5/5||5/5||5/5||2016||6,499||latest||check|
|Nikon D810 (⇒ lft | rgt)||-||86/100 Gold||5/5||4.5/5||4.5/5||2014||3,299||discont.||check|
|Nikon D3S (⇒ lft | rgt)||-||89/100 Gold||4.5/5||5/5||5/5||2009||5,199||discont.||check|
|Pentax 645Z (⇒ lft | rgt)||-||-||4.5/5||5/5||5/5||2014||8,499||latest||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|
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. Hence, a score should always be seen in the context of the camera's market launch date and its price, and rating-comparisons among cameras that span long time periods or concern very differently equipped models make little sense. It should also be noted that some of the review sites have over time altered the way they render their verdicts.
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 you cannot find the camera you are interested in, kindly get in touch, and I will try to update the database with the necessary infos.
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