Pentax 645D vs Sony A7R

The Pentax 645D and the Sony Alpha A7R are two digital cameras that were officially introduced, respectively, in March 2010 and October 2013. The 645D is a DSLR, while the A7R is a mirrorless interchangeable lens camera. The cameras are based on a medium format (645D) and a full frame (A7R) sensor. The Pentax has a resolution of 39.5 megapixels, whereas the Sony provides 36.2 MP.

Below is an overview of the main specs of the two cameras as a starting point for the comparison.

Headline Specifications

Pentax 645D		Sony A7R
Digital single lens reflex		Mirrorless system camera
Pentax 645 mount lenses		Sony E mount lenses
39.5 MP – Medium Format sensor		36.2 MP – Full Frame sensor
no Video		1080/60p Video
ISO 100-1,600		ISO 100-25,600 (50 - 51,200)
Optical viewfinder		Electronic viewfinder (2400k dots)
3.0" LCD – 921k dots		3.0" LCD – 1230k dots
Fixed screen (not touch-sensitive)		Tilting screen (no touchscreen)
1.1 shutter flaps per second		4 shutter flaps per second
Weathersealed body		Weathersealed body
800 shots per battery charge		340 shots per battery charge
156 x 117 x 119 mm, 1480 g		127 x 94 x 48 mm, 465 g

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Going beyond this snapshot of core features and characteristics, what are the differences between the Pentax 645D and the Sony Alpha A7R? Which one should you buy? Read on to find out how these two cameras compare with respect to their body size, their imaging sensors, their shooting features, their input-output connections, and their reception by expert reviewers.

Body comparison

The physical size and weight of the Pentax 645D and the Sony A7R are illustrated in the side-by-side display below. 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 size dimensions are rounded to the nearest millimeter.

If the front view area (width x height) of the cameras is taken as an aggregate measure of their size, the Sony A7R is considerably smaller (35 percent) than the Pentax 645D. Moreover, the A7R is substantially lighter (69 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 and compare 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 645D gets 800 shots out of its D-LI90 battery, while the A7R can take 340 images on a single charge of its NP-FW50 power pack. The power pack in the A7R can be charged via the USB port, which can be very convenient when travelling.

The adjacent table lists the principal physical characteristics of the two cameras alongside a wider set of alternatives. In case you want to display and compare another camera duo, you can use the CAM-parator app to select your camera combination among a large number of options.

Body Specifications

		Camera Model	Camera Width	Camera Height	Camera Depth	Camera Weight	Battery Life	Weather Sealing	Camera Launch	Launch Price (USD)	Street Price
1.		Pentax 645D	156 mm	117 mm	119 mm	1480 g	800	Y	Mar 2010	9,995	ebay.com
2.		Sony A7R	127 mm	94 mm	48 mm	465 g	340	Y	Oct 2013	2,299	ebay.com
3.		Canon 1D X Mark II	158 mm	168 mm	83 mm	1530 g	1210	Y	Feb 2016	5,999	ebay.com
4.		Canon 1D X	158 mm	168 mm	83 mm	1551 g	1120	Y	Oct 2011	6,799	ebay.com
5.		Canon 1D Mark IV	156 mm	157 mm	80 mm	1230 g	1500	Y	Oct 2009	4,999	ebay.com
6.		Leica S Typ 006	160 mm	120 mm	80 mm	1260 g	..	Y	Sep 2012	21,950	ebay.com
7.		Nikon D850	146 mm	124 mm	79 mm	1005 g	1840	Y	Jul 2017	3,299	amazon.com
8.		Nikon D5	160 mm	159 mm	92 mm	1415 g	3780	Y	Jan 2016	6,499	ebay.com
9.		Nikon D810	146 mm	123 mm	82 mm	980 g	1200	Y	Jun 2014	3,299	ebay.com
10.		Nikon D3S	160 mm	157 mm	88 mm	1240 g	4200	Y	Oct 2009	5,199	ebay.com
11.		Pentax 645Z	156 mm	117 mm	123 mm	1550 g	650	Y	Apr 2014	8,499	amazon.com
12.		Sony A7R II	127 mm	96 mm	60 mm	625 g	290	Y	Jun 2015	3,199	ebay.com
13.		Sony A7 II	127 mm	96 mm	60 mm	599 g	350	Y	Nov 2014	1,999	ebay.com
14.		Sony A7S	127 mm	94 mm	48 mm	489 g	380	Y	Apr 2014	2,499	ebay.com
15.		Sony A7	127 mm	94 mm	48 mm	474 g	340	Y	Oct 2013	1,699	ebay.com
16.		Sony RX1R	113 mm	65 mm	70 mm	482 g	270	n	Jun 2013	2,799	ebay.com
Note: Measurements and pricing do not include easily detachable parts, such as add-on or interchangeable lenses or optional viewfinders.
Convert to Imperial

Any camera decision will obviously take relative prices into account. 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 A7R was launched at a markedly lower price (by 77 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.

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 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 a full frame sensor. The sensor area in the A7R 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 offers a 3:2 aspect.

With 39.5MP, the 645D offers a slightly higher resolution than the A7R (36.2MP), but the 645D nevertheless has larger individual pixels (pixel pitch of 6.06μm versus 4.88μm for the A7R) due to its larger sensor. However, the A7R is a much more recent model (by 3 years and 7 months) than the 645D, and its sensor will 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.

The Pentax 645D has a native sensitivity range from ISO 100 to ISO 1600. The corresponding ISO settings for the Sony Alpha A7R are ISO 100 to ISO 25600, with the possibility to increase the ISO range to 50-51200.

In terms of underlying technology, the 645D is build around a CCD sensor, while the A7R uses a CMOS imager. Both cameras use a Bayer filter for capturing RGB colors on a square grid of photosensors. This arrangement is found in most digital cameras.

Consistent information on actual sensor performance is available from DXO Mark for many cameras. 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 offers substantially better image quality than the 645D (overall score 13 points higher). The advantage is based on 1 bits higher color depth, 1.5 EV in additional dynamic range, and 1.1 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 Model	Sensor Class	Resolution (MP)	Horiz. Pixels	Vert. Pixels	Video Format	DXO Portrait	DXO Landscape	DXO Sports	DXO Overall
1.		Pentax 645D	Medium Format	39.5	7264	5440	none	24.6	12.6	1262	82
2.		Sony A7R	Full Frame	36.2	7360	4912	1080/60p	25.6	14.1	2746	95
3.		Canon 1D X Mark II	Full Frame	20.0	5472	3648	4K/60p	24.1	13.5	3207	88
4.		Canon 1D X	Full Frame	17.9	5184	3456	1080/30p	23.8	11.8	2786	82
5.		Canon 1D Mark IV	APS-H	16.0	4896	3264	1080/30p	22.8	12.0	1320	74
6.		Leica S Typ 006	Medium Format	37.5	7500	5000	none	23.9	12.2	824	76
7.		Nikon D850	Full Frame	45.4	8256	5504	4K/30p	26.4	14.8	2660	100
8.		Nikon D5	Full Frame	20.7	5588	3712	4K/30p	25.1	12.3	2343	88
9.		Nikon D810	Full Frame	36.2	7360	4912	1080/60p	25.7	14.8	2853	97
10.		Nikon D3S	Full Frame	12.1	4256	2832	720/24p	23.5	12.0	3253	82
11.		Pentax 645Z	Medium Format	51.1	8256	6192	1080/60i	26.0	14.7	4505	101
12.		Sony A7R II	Full Frame	42.2	7952	5304	4K/30p	26.0	13.9	3434	98
13.		Sony A7 II	Full Frame	24.0	6000	4000	1080/60p	24.9	13.6	2449	90
14.		Sony A7S	Full Frame	12.0	4240	2832	1080/60p	23.9	13.2	3702	87
15.		Sony A7	Full Frame	24.0	6000	4000	1080/60p	24.8	14.2	2248	90
16.		Sony RX1R	Full Frame	24.0	6000	4000	1080/60p	25.0	13.6	2537	91

Many modern cameras are not only capable of taking still images, but can also record movies. The A7R indeed provides for movie recording, while the 645D does not. The highest resolution format that the A7R can use is 1080/60p.

Feature comparison

Beyond body and sensor, cameras can and do differ across a range of features. For example, the A7R has an electronic viewfinder (2400k 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 viewfinder in the A7R offers a wider field of view (100%) than the one in the 645D (98%), so that a larger proportion of the captured image is visible in the finder. On the other hand, the viewfinder of the 645D has a higher magnification (0.78x vs 0.71x), so that the size of the image transmitted appears closer to the size seen with the naked human eye. The adjacent table lists some of the other core features of the Pentax 645D and Sony A7R along with similar information for a selection of comparators.

Core Features

		Camera Model	Viewfinder (Type or 000 dots)	Control Panel (yes/no)	LCD Specifications (inch/000 dots)	LCD Attach- ment	Touch Screen (yes/no)	Max Shutter Speed *	Max Shutter Flaps *	Built-in Flash (yes/no)	Built-in Image Stab
1.		Pentax 645D	optical	Y	3.0 / 921	fixed	n	1/4000s	1.1/s	n	n
2.		Sony A7R	2400	n	3.0 / 1230	tilting	n	1/8000s	4.0/s	n	n
3.		Canon 1D X Mark II	optical	Y	3.2 / 1620	fixed	Y	1/8000s	16.0/s	n	n
4.		Canon 1D X	optical	Y	3.2 / 1040	fixed	n	1/8000s	14.0/s	n	n
5.		Canon 1D Mark IV	optical	Y	3.0 / 920	fixed	n	1/8000s	10.0/s	n	n
6.		Leica S Typ 006	optical	Y	3.0 / 922	fixed	n	1/4000s	1.5/s	n	n
7.		Nikon D850	optical	Y	3.2 / 2359	tilting	Y	1/8000s	9.0/s	n	n
8.		Nikon D5	optical	Y	3.2 / 2359	fixed	Y	1/8000s	14.0/s	n	n
9.		Nikon D810	optical	Y	3.2 / 1229	fixed	n	1/8000s	5.0/s	Y	n
10.		Nikon D3S	optical	Y	3.0 / 921	fixed	n	1/8000s	11.0/s	n	n
11.		Pentax 645Z	optical	Y	3.2 / 1037	tilting	n	1/4000s	3.0/s	n	n
12.		Sony A7R II	2400	n	3.0 / 1229	tilting	n	1/8000s	5.0/s	n	Y
13.		Sony A7 II	2400	n	3.0 / 1230	tilting	n	1/8000s	5.0/s	n	Y
14.		Sony A7S	2400	n	3.0 / 921	tilting	n	1/8000s	5.0/s	n	n
15.		Sony A7	2400	n	3.0 / 1230	tilting	n	1/8000s	5.0/s	n	n
16.		Sony RX1R	optional	n	3.0 / 1229	fixed	n	1/4000s	5.0/s	Y	n
Notes: *) Information refers to the mechanical shutter, unless the camera only has an electronic one.

One feature that is present on the 645D, but is missing on the A7R 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 Pentax 645D has an intervalometer built-in. This enables the photographer to capture time lapse sequences, such as flower blooming, a sunset or moon rise, without purchasing an external camera trigger and related software.

The 645D writes its imaging data to SDXC cards, while the A7R uses SDXC or Memory Stick PRO Duo cards. The 645D features dual card slots, which can be very useful in case a memory card fails. In contrast, the A7R only has one slot. The A7R supports UHS-I cards (Ultra High Speed data transfer of up to 104 MB/s), while the 645D cannot take advantage of Ultra High Speed SD cards.

Connectivity comparison

For some imaging applications, the extent to which a camera can communicate with its environment can be an important aspect in the camera decision process. The table below provides an overview of the connectivity of the Pentax 645D and Sony Alpha A7R and, in particular, the interfaces the cameras (and selected comparators) provide for accessory control and data transfer.

Input-Output Connections

		Camera Model	Hotshoe Port	Internal Mic / Speaker	Microphone Port	Headphone Port	HDMI Port	USB Port	WiFi Support	NFC Support	Bluetooth Support
1.		Pentax 645D	Y	stereo / -	-	-	-	2.0	-	-	-
2.		Sony A7R	Y	stereo / mono	Y	Y	micro	2.0	Y	Y	-
3.		Canon 1D X Mark II	Y	mono / mono	Y	Y	mini	3.0	-	-	-
4.		Canon 1D X	Y	mono / -	Y	-	mini	2.0	-	-	-
5.		Canon 1D Mark IV	Y	stereo / -	Y	-	mini	2.0	-	-	-
6.		Leica S Typ 006	Y	- / -	-	-	mini	2.0	-	-	-
7.		Nikon D850	Y	stereo / mono	Y	Y	mini	3.0	Y	Y	Y
8.		Nikon D5	Y	stereo / mono	Y	Y	mini	3.0	-	-	-
9.		Nikon D810	Y	stereo / mono	Y	Y	mini	3.0	Y	-	-
10.		Nikon D3S	Y	stereo / -	-	-	mini	2.0	-	-	-
11.		Pentax 645Z	Y	stereo / mono	Y	-	mini	3.0	-	-	-
12.		Sony A7R II	Y	stereo / mono	Y	Y	micro	2.0	Y	Y	-
13.		Sony A7 II	Y	stereo / mono	Y	Y	micro	2.0	Y	Y	-
14.		Sony A7S	Y	stereo / mono	Y	Y	micro	2.0	Y	Y	-
15.		Sony A7	Y	stereo / mono	Y	Y	micro	2.0	Y	Y	-
16.		Sony RX1R	Y	stereo / mono	Y	-	mini	2.0	-	-	-

It is notable that the A7R offers wifi support, which can be a very convenient means to transfer image data to an off-camera location. In contrast, the 645D does not provide wifi capability.

Studio photographers will appreciate that the Pentax 645D (unlike the A7R) features a PC Sync socket, so that professional strobe lights can be controlled by the camera.

Both the 645D and the A7R have been discontinued, but can regularly be found used on ebay. The 645D was replaced by the Pentax 645Z, while the A7R was followed by the Sony A7R II. Further information on the features and operation of the 645D and A7R can be found, respectively, in the Pentax 645D Manual (free pdf) or the online Sony A7R Manual.

Review summary

So how do things add up? Which of the two cameras – the Pentax 645D or the Sony A7R – has the upper hand? Is one clearly better than the other? The listing below highlights the relative strengths of the two models.

Arguments in favor of the Pentax 645D:

• Brighter framing: Features an optical viewfinder for clear, lag-free composition.
• Larger viewfinder image: Features a viewfinder with a higher magnification (0.78x vs 0.71x).
• Easier setting verification: Features an LCD display on top to control shooting parameters.
• Easier time-lapse photography: Has an intervalometer built-in for low frequency shooting.
• Longer lasting: Can take more shots (800 versus 340) on a single battery charge.
• Better studio light control: Has a PC Sync socket to connect to professional strobe lights.
• Greater peace of mind: Features a second card slot as a backup in case of memory card failure.
• More heavily discounted: Has been available for much longer (launched in March 2010).

Advantages of the Sony Alpha A7R:

• Better image quality: Scores substantially higher (13 points) in the DXO overall evaluation.
• More dynamic range: Captures a broader range of light and dark details (1.5 EV of extra DR).
• Better low-light sensitivity: Can shoot in dim conditions (1.1 stops ISO advantage).
• Broader imaging potential: Can capture not only stills but also 1080/60p video.
• More framing info: Has an electronic viewfinder that displays shooting data.
• More complete view: Has a viewfinder with a larger field of view (100% vs 98%).
• More detailed LCD: Has a higher resolution rear screen (1230k vs 921k dots).
• More flexible LCD: Has a tilting screen for odd-angle shots in landscape orientation.
• Faster shutter: Has higher mechanical shutter speed (1/8000s vs 1/4000s) to freeze action.
• Faster burst: Shoots at higher frequency (4 vs 1.1 flaps/sec) to capture the decisive moment.
• More compact: Is smaller (127x94mm vs 156x117mm) and will fit more readily into a bag.
• Less heavy: Has a lower weight (by 1015g or 69 percent) and is thus easier to take along.
• Easier travel charging: Can be conveniently charged via its USB port.
• More legacy lens friendly: Can use many non-native lenses via adapters.
• Easier file upload: Has wifi built in for automatic backup or image transfer to the web.
• Easier device pairing: Supports NFC for fast wireless image transfer over short distances.
• Faster buffer clearing: Has an SD card interface that supports the UHS-I standard.
• More affordable: Was introduced into a lower priced category (77 percent cheaper at launch).
• More modern: Reflects 3 years and 7 months of technical progress since the 645D launch.

If the number of relative strengths (bullet points above) is taken as a guide, the A7R is the clear winner of the contest (19 : 8 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 when reflecting and deciding on a new camera. A professional wedding photographer will view the differences between cameras in a way that diverges from the perspective of a travel photog, and a person interested in cityscapes has distinct needs from a macro shooter. Hence, the decision which camera is best and worth buying is often a very personal one.

How about other alternatives? Do the specifications of the Pentax 645D and the Sony A7R place the cameras among the top in their class? Find out in the latest Best DSLR Camera and Best Mirrorless Interchangeable Lens Camera listings whether the two cameras rank among the cream of the crop.

In any case, while the comparison of the spec-sheets of cameras can offer a general idea of their imaging potential, it remains partial and cannot reveal, for example, the shooting experience and imaging performance when actually working with the 645D or the A7R. 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.

Expert reviews

This is why expert reviews are important. The adjacent summary-table relays the overall verdicts of several of the most popular camera review sites (amateurphotographer [AP], cameralabs [CL], digitalcameraworld [DCW], dpreview [DPR], ephotozine [EPZ], photographyblog [PB]). As can be seen, the professional reviewers agree in many cases on the quality of different cameras, but sometimes their assessments diverge, reinforcing the earlier point that a camera decision is often a very personal choice.

Expert Camera Reviews

		Camera   Model	AP   score	CL   score	DCW   score	DPR   score	EPZ   score	PB   score	Camera Launch	Launch Price (USD)	Street Price
1.		Pentax 645D	5/5	..	..	..	..	..	Mar 2010	9,995	ebay.com
2.		Sony A7R	5/5	+ +	..	82/100	4.5/5	5/5	Oct 2013	2,299	ebay.com
3.		Canon 1D X Mark II	..	..	4.5/5	89/100	4.5/5	4.5/5	Feb 2016	5,999	ebay.com
4.		Canon 1D X	5/5	..	..	..	4.5/5	4.5/5	Oct 2011	6,799	ebay.com
5.		Canon 1D Mark IV	5/5	..	..	89/100	..	..	Oct 2009	4,999	ebay.com
6.		Leica S Typ 006	..	..	..	..	..	..	Sep 2012	21,950	ebay.com
7.		Nikon D850	4.5/5	+ +	5/5	89/100	4.5/5	5/5	Jul 2017	3,299	amazon.com
8.		Nikon D5	..	..	4/5	89/100	4.5/5	5/5	Jan 2016	6,499	ebay.com
9.		Nikon D810	5/5	..	5/5	86/100	5/5	4.5/5	Jun 2014	3,299	ebay.com
10.		Nikon D3S	5/5	..	..	89/100	4.5/5	5/5	Oct 2009	5,199	ebay.com
11.		Pentax 645Z	5/5	..	3.5/5	..	4.5/5	5/5	Apr 2014	8,499	amazon.com
12.		Sony A7R II	5/5	+ +	5/5	90/100	5/5	5/5	Jun 2015	3,199	ebay.com
13.		Sony A7 II	5/5	+	4/5	82/100	4.5/5	5/5	Nov 2014	1,999	ebay.com
14.		Sony A7S	4/5	..	..	86/100	4.5/5	5/5	Apr 2014	2,499	ebay.com
15.		Sony A7	5/5	+ +	..	80/100	5/5	5/5	Oct 2013	1,699	ebay.com
16.		Sony RX1R	5/5	..	..	..	4/5	4.5/5	Jun 2013	2,799	ebay.com
Notes: (+ +) highly recommended; (+) recommended; (o) reviewed; (..) not available.

Care should be taken when interpreting the review scores above, though. The ratings are only valid when referring to cameras in the same category and of the same age. Thus, a score needs to be put into the context of the launch date and the launch price of the camera, and comparisons of ratings among very different cameras or across long time periods have little meaning. Also, please note that some of the review sites have changed their methodology and reporting over time.

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Other camera comparisons

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