Pentax 645Z vs 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 (A7S II) sensor. The Pentax has a resolution of 51.1 megapixels, whereas the Sony provides 12 MP.

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

Headline Specifications

Pentax 645Z		Sony A7S II
Digital single lens reflex		Mirrorless system camera
Pentax 645 mount lenses		Sony E mount lenses
51.1 MP, Medium Format Sensor		12 MP, Full Frame Sensor
1080/60i Video		4K/30p Video
ISO 100-204,800		ISO 100-102,400 (50 - 409,600)
Optical viewfinder		Electronic viewfinder (2400k dots)
3.2 LCD, 1037k dots		3.0 LCD, 1229k dots
Tilting screen (no touchscreen)		Tilting screen (not touch-sensitive)
3 shutter flaps per second		5 shutter flaps per second
Lens stabilization only		In-body stabilization
Weathersealed body		Weathersealed body
650 shots per battery charge		370 shots per battery charge
156 x 117 x 123 mm, 1550 g		127 x 96 x 60 mm, 627 g

Going beyond this snapshot of core features and characteristics, what are the differences between the Pentax 645Z and the Sony Alpha 7S II? 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 645Z and the Sony A7S II 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 width, height and depth 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 A7S II is considerably 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 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 645Z gets 650 shots out of its D-LI90 battery, while the A7S II can take 370 images on a single charge of its NP-FW50 power pack. The power pack in the A7S II 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
	Pentax 645Z	6.1 in	4.6 in	4.8 in	54.7 oz	650	Y	Apr 2014	8,499
	Sony A7S II	5.0 in	3.8 in	2.4 in	22.1 oz	370	Y	Sep 2015	2,999
	Canon 1D X Mark II	6.2 in	6.6 in	3.3 in	54.0 oz	1210	Y	Feb 2016	5,999
	Canon 5DS	6.0 in	4.6 in	3.0 in	32.8 oz	700	Y	Feb 2015	3,699
	Canon 5DS R	6.0 in	4.6 in	3.0 in	32.8 oz	700	Y	Feb 2015	3,699
	Hasselblad X1D	5.9 in	3.9 in	2.8 in	25.6 oz	..	Y	Jun 2016	8,995
	Leica SL	5.8 in	4.1 in	1.5 in	29.9 oz	400	Y	Oct 2015	7,450
	Nikon D850	5.7 in	4.9 in	3.1 in	35.5 oz	1840	Y	Jul 2017	3,299
	Nikon D5	6.3 in	6.3 in	3.6 in	49.9 oz	3780	Y	Jan 2016	6,499
	Nikon D7200	5.4 in	4.2 in	3.0 in	27.0 oz	1110	Y	Mar 2015	1,199
	Nikon D4S	6.3 in	6.2 in	3.6 in	47.6 oz	3020	Y	Feb 2014	6,499
	Pentax 645D	6.1 in	4.6 in	4.7 in	52.2 oz	800	Y	Mar 2010	9,995
	Sony A7S III	5.0 in	3.8 in	3.2 in	24.7 oz	600	Y	Jul 2020	3,499
	Sony A99 II	5.6 in	4.1 in	3.0 in	29.9 oz	490	Y	Sep 2016	3,199
	Sony A7R II	5.0 in	3.8 in	2.4 in	22.0 oz	290	Y	Jun 2015	3,199
	Sony A7 II	5.0 in	3.8 in	2.4 in	21.1 oz	350	Y	Nov 2014	1,999
	Sony A7S	5.0 in	3.7 in	1.9 in	17.2 oz	380	Y	Apr 2014	2,499
Notes: Measurements and pricing do not include easily detachable parts, such as add-on or interchangeable lenses or optional viewfinders.
Convert to Metric

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 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.

Sensor comparison

The size of the imaging sensor is a crucial determinant 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 tend 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.

Technology-wise, both cameras are equipped with CMOS (Complementary Metal–Oxide–Semiconductor) sensors.

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.

The resolution advantage of the Pentax 645Z implies greater flexibility for cropping images or the possibility to print larger pictures. The maximum print size of the 645Z for good quality output (200 dots per inch) amounts to 41.3 x 31 inches or 104.9 x 78.6 cm, for very good quality (250 dpi) 33 x 24.8 inches or 83.9 x 62.9 cm, and for excellent quality (300 dpi) 27.5 x 20.6 inches or 69.9 x 52.4 cm. The corresponding values for the Sony A7S II are 21.2 x 14.2 inches or 53.8 x 36 cm for good quality, 17 x 11.3 inches or 43.1 x 28.8 cm for very good quality, and 14.1 x 9.4 inches or 35.9 x 24 cm for excellent quality prints.

The Pentax 645Z has a native sensitivity range from ISO 100 to ISO 204800. The corresponding ISO settings for the Sony Alpha 7S II are ISO 100 to ISO 102400, with the possibility to increase the ISO range to 50-409600.

Since 2007, DXO Mark has published sensor performance measurements that have been derived using a consistent methodology. 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 Model	Sensor Class	Resolution (MP)	Horiz. Pixels	Vert. Pixels	Video Format	DXO Portrait	DXO Landscape	DXO Sports	DXO Overall
	Pentax 645Z	Medium Format	51.1	8256	6192	1080/60i	26.0	14.7	4505	101
	Sony A7S II	Full Frame	12.0	4240	2832	4K/30p	23.6	13.3	2993	85
	Canon 1D X Mark II	Full Frame	20.0	5472	3648	4K/60p	24.1	13.5	3207	88
	Canon 5DS	Full Frame	50.3	8688	5792	1080/30p	24.7	12.4	2381	87
	Canon 5DS R	Full Frame	50.3	8688	5792	1080/30p	24.6	12.4	2308	86
	Hasselblad X1D	Medium Format	51.3	8272	6200	1080/25p	26.2	14.8	4489	102
	Leica SL	Full Frame	24.0	6000	4000	4K/30p	25.0	13.4	1821	88
	Nikon D850	Full Frame	45.4	8256	5504	4K/30p	26.4	14.8	2660	100
	Nikon D5	Full Frame	20.7	5588	3712	4K/30p	25.1	12.3	2343	88
	Nikon D7200	APS-C	24.0	6000	4000	1080/60p	24.5	14.6	1333	87
	Nikon D4S	Full Frame	16.2	4928	3280	1080/60p	24.4	13.3	3074	89
	Pentax 645D	Medium Format	39.5	7264	5440	none	24.6	12.6	1262	82
	Sony A7S III	Full Frame	12.0	4240	2832	4K/120p	..	..	..	..
	Sony A99 II	Full Frame	42.2	7952	5304	4K/30p	25.4	13.4	2317	92
	Sony A7R II	Full Frame	42.2	7952	5304	4K/30p	26.0	13.9	3434	98
	Sony A7 II	Full Frame	24.0	6000	4000	1080/60p	24.9	13.6	2449	90
	Sony A7S	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. Both cameras under consideration are equipped with sensors that have a sufficiently high read-out speed for moving images, 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

Apart from body and sensor, cameras can and do differ across a variety 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 viewfinders of both cameras offer the same magnification (0.78x), but the one in the A7S II has a wider field of view (100%) than the finder in the 645Z (98%), so that a larger proportion of the captured image is visible. The following table reports on some other key feature differences and similarities of the Pentax 645Z, the Sony A7S II, and comparable cameras.

Core Features

	Camera Model	Viewfinder (Type or 000 dots)	Control Panel (yes/no)	LCD Size (inch)	LCD Resolution (000 dots)	LCD Attach- ment	Touch Screen (yes/no)	Mech Shutter Speed	Shutter Flaps (1/sec)	Built-in Flash (yes/no)	Built-in Image Stab
	Pentax 645Z	optical	Y	3.2	1037	tilting	n	1/4000s	3.0	n	n
	Sony A7S II	2400	n	3.0	1229	tilting	n	1/8000s	5.0	n	Y
	Canon 1D X Mark II	optical	Y	3.2	1620	fixed	Y	1/8000s	16.0	n	n
	Canon 5DS	optical	Y	3.2	1040	fixed	n	1/8000s	5.0	n	n
	Canon 5DS R	optical	Y	3.2	1040	fixed	n	1/8000s	5.0	n	n
	Hasselblad X1D	2360	n	3.0	920	fixed	Y	1/2000s	2.3	n	n
	Leica SL	4400	Y	3.0	1040	fixed	Y	1/8000s	11.0	n	n
	Nikon D850	optical	Y	3.2	2359	tilting	Y	1/8000s	9.0	n	n
	Nikon D5	optical	Y	3.2	2359	fixed	Y	1/8000s	14.0	n	n
	Nikon D7200	optical	Y	3.2	1229	fixed	n	1/8000s	6.0	Y	n
	Nikon D4S	optical	Y	3.2	921	fixed	n	1/8000s	11.0	n	n
	Pentax 645D	optical	Y	3.0	921	fixed	n	1/4000s	1.1	n	n
	Sony A7S III	9440	n	3.0	1440	swivel	Y	1/8000s	10.0	n	Y
	Sony A99 II	2400	Y	3.0	1229	full-flex	n	1/8000s	12.0	n	Y
	Sony A7R II	2400	n	3.0	1229	tilting	n	1/8000s	5.0	n	Y
	Sony A7 II	2400	n	3.0	1230	tilting	n	1/8000s	5.0	n	Y
	Sony A7S	2400	n	3.0	921	tilting	n	1/8000s	5.0	n	n

One feature that is present on the 645Z, but is missing on the A7S II 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 reported shutter speed information refers to the use of the mechanical shutter. Yet, some cameras only have an electronic shutter, while others have an electronic shutter in addition to a mechanical one. In fact, the A7S II is one of those camera that have an additional electronic shutter, which makes completely silent shooting possible. However, this mode is less suitable for photographing moving objects (risk of rolling shutter) or shooting under artificial light sources (risk of flickering).

The Pentax 645Z 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 645Z writes its imaging data to SDXC cards, while the A7S II uses SDXC or Memory Stick PRO Duo cards. The 645Z features dual card slots, which can be very useful in case a memory card fails. In contrast, the A7S II only has one slot. Both cameras can use UHS-I cards, which provide for Ultra High Speed data transfer of up to 104 MB/s.

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 645Z and Sony Alpha 7S II 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 Microphone	Internal Speaker	Microphone Port	Headphone Port	HDMI Port	USB Port	WiFi Support	NFC Support	Bluetooth Support
	Pentax 645Z	Y	stereo	mono	Y	-	mini	3.0	-	-	-
	Sony A7S II	Y	stereo	mono	Y	Y	micro	2.0	Y	Y	-
	Canon 1D X Mark II	Y	mono	mono	Y	Y	mini	3.0	-	-	-
	Canon 5DS	Y	mono	mono	Y	-	mini	3.0	-	-	-
	Canon 5DS R	Y	mono	mono	Y	-	mini	3.0	-	-	-
	Hasselblad X1D	Y	stereo	mono	Y	Y	mini	3.0	Y	-	-
	Leica SL	Y	stereo	mono	Y	Y	full	3.0	Y	-	-
	Nikon D850	Y	stereo	mono	Y	Y	mini	3.0	Y	Y	Y
	Nikon D5	Y	stereo	mono	Y	Y	mini	3.0	-	-	-
	Nikon D7200	Y	stereo	mono	Y	Y	mini	2.0	Y	Y	-
	Nikon D4S	Y	mono	mono	Y	Y	mini	2.0	-	-	-
	Pentax 645D	Y	stereo	-	-	-	-	2.0	-	-	-
	Sony A7S III	Y	stereo	mono	Y	Y	full	3.2	Y	-	Y
	Sony A99 II	Y	stereo	mono	Y	Y	micro	2.0	Y	Y	Y
	Sony A7R II	Y	stereo	mono	Y	Y	micro	2.0	Y	Y	-
	Sony A7 II	Y	stereo	mono	Y	Y	micro	2.0	Y	Y	-
	Sony A7S	Y	stereo	mono	Y	Y	micro	2.0	Y	Y	-

It is notable that the A7S II offers wifi support, which can be a very convenient means to transfer image data to an off-camera location. In contrast, the 645Z does not provide wifi capability.

Studio photographers will appreciate that the Pentax 645Z (unlike the A7S II) features a PC Sync socket, so that professional strobe lights can be controlled by the camera.

The 645Z is a recent model that features in the current product line-up of Pentax. In contrast, the A7S II has been discontinued (but can be found pre-owned on eBay). As a replacement in the same line of cameras, the A7S II was succeeded by the Sony A7S III. Further information on the two cameras (e.g. user guides, manuals), as well as related accessories, can be found on the official Pentax and Sony websites.

Review summary

So what is the bottom line? Is there a clear favorite between the Pentax 645Z and the Sony A7S II? Which camera is better? A synthesis of the relative strong points of each of the models is listed below.

Reasons to prefer 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: Features 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.
• Easier time-lapse photography: Has an intervalometer built-in for low frequency shooting.
• Longer lasting: Can take more shots (650 versus 370) on a single battery charge.
• Faster data transfer: Supports a more advanced USB protocol (3.0 vs 2.0).
• 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 on the market for longer (launched in April 2014).

Arguments in favor 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).
• Better sound control: Has a headphone port that enables audio monitoring while recording.
• 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 (1229k vs 1037k dots).
• Faster shutter: Has higher mechanical shutter speed (1/8000s vs 1/4000s) to freeze action.
• Faster burst: Shoots at higher frequency (5 vs 3 flaps/sec) to capture the decisive moment.
• Less disturbing: Has an electronic shutter option for completely silent shooting.
• 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.
• Easier travel charging: Can be conveniently charged via its USB port.
• Sharper images: Has stabilization technology built-in to reduce the impact of hand-shake.
• 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.
• 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 count of individual advantages (bullet points above) is taken as a guide, the A7S II is the clear winner of the contest (19 : 15 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 645Z and the Sony A7S II 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 specs-based evaluation of cameras can be instructive in revealing their potential as photographic tools, it says little about, for example, the shooting experience and imaging performance of the 645Z and the A7S II 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.

Expert reviews

This is where reviews by experts come in. The table below provides a synthesis of the camera assessments of some of the best known photo-gear review sites (cameralabs, dpreview, ephotozine, imaging-resource, and photographyblog). 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.

Review Scores

	Camera Model	camera   labs	dp review	ephoto   zine	imaging resource	photography   blog	Camera Launch	Launch Price (USD)	Street Price
	Pentax 645Z	..	..	4.5/5	5/5	5/5	Apr 2014	8,499
	Sony A7S II	+	..	4.5/5	5/5	5/5	Sep 2015	2,999
	Canon 1D X Mark II	..	89/100	4.5/5	5/5	4.5/5	Feb 2016	5,999
	Canon 5DS	+	83/100	4.5/5	5/5	4.5/5	Feb 2015	3,699
	Canon 5DS R	+	83/100	5/5	5/5	4.5/5	Feb 2015	3,699
	Hasselblad X1D	o	81/100	..	..	4/5	Jun 2016	8,995
	Leica SL	..	84/100	4.5/5	4/5	4/5	Oct 2015	7,450
	Nikon D850	+ +	89/100	4.5/5	5/5	5/5	Jul 2017	3,299
	Nikon D5	..	89/100	4.5/5	5/5	5/5	Jan 2016	6,499
	Nikon D7200	+ +	84/100	4.5/5	4/5	4.5/5	Mar 2015	1,199
	Nikon D4S	..	..	4.5/5	5/5	4.5/5	Feb 2014	6,499
	Pentax 645D	..	..	..	4.5/5	..	Mar 2010	9,995
	Sony A7S III	+ +	..	4.5/5	..	5/5	Jul 2020	3,499
	Sony A99 II	..	85/100	4.5/5	4.5/5	4.5/5	Sep 2016	3,199
	Sony A7R II	+ +	90/100	5/5	4.5/5	5/5	Jun 2015	3,199
	Sony A7 II	+	82/100	4.5/5	5/5	5/5	Nov 2014	1,999
	Sony A7S	..	86/100	4.5/5	4.5/5	5/5	Apr 2014	2,499
Notes: (+ +) highly recommended; (+) recommended; (o) reviewed; (..) not available.

Care should be taken when interpreting the review scores above, though. The assessments were made in relation to similar cameras of the same technological generation. Thus, a score needs to be put into the context of the launch date and the launch price 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, please note that some of the review sites have changed their methodology and reporting over time.

Other camera comparisons

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Specifications: Pentax 645Z vs Sony A7S II

Below is a side-by-side comparison of the specs of the two cameras to facilitate a quick review of their differences and common features.

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