Pentax 645Z vs Ricoh GR III

The Pentax 645Z and the Ricoh GR III are two digital cameras that were officially introduced, respectively, in April 2014 and February 2019. The 645Z is a DSLR, while the GR III is a fixed lens compact. The cameras are based on a medium format (645Z) and an APS-C (GR III) sensor. The Pentax has a resolution of 51.1 megapixels, whereas the Ricoh provides 24 MP.

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

Headline Specifications

Pentax 645Z		Ricoh GR III
Digital single lens reflex		Fixed lens compact camera
Pentax 645 mount lenses		28mm f/2.8
51.1 MP – Medium Format sensor		24 MP – APS-C sensor
1080/60i Video		1080/60p Video
ISO 100-204,800		ISO 100-102,400
Optical viewfinder		Viewfinder optional
3.2" LCD – 1037k dots		3.0" LCD – 1037k dots
Tilting screen (no touchscreen)		Fixed touchscreen
3 shutter flaps per second		4 shutter flaps per second
Lens stabilization only		In-body stabilization
Weathersealed body		not weather sealed
650 shots per battery charge		200 shots per battery charge
156 x 117 x 123 mm, 1550 g		109 x 62 x 33 mm, 257 g

Check 645Z offers at
ebay.com
Check GR III price at
amazon.com

Going beyond this snapshot of core features and characteristics, what are the differences between the Pentax 645Z and the Ricoh GR III? 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

An illustration of the physical size and weight of the Pentax 645Z and the Ricoh GR III is provided in the side-by-side display below. The two cameras are presented according to their relative size. 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.

If the front view area (width x height) of the cameras is taken as an aggregate measure of their size, the Ricoh GR III is considerably smaller (63 percent) than the Pentax 645Z. It is worth mentioning in this context that the 645Z is splash and dust resistant, while the GR III does not feature any corresponding weather-sealing.

The above size and weight comparisons are to some extent incomplete and possibly misleading, as the GR III has a lens built in, whereas the 645Z is an interchangeable lens camera that requires a separate lens. Attaching the latter will add extra weight and bulk to the setup.

Concerning battery life, the 645Z gets 650 shots out of its Pentax D-LI90 battery, while the GR III can take 200 images on a single charge of its Ricoh DB-110 power pack. The power pack in the GR III can be charged via the USB port, which can be very convenient when travelling.

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, you can move across to the CAM-parator tool and choose from the broad selection of possible camera comparisons there.

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 645Z	156 mm	117 mm	123 mm	1550 g	650	Y	Apr 2014	8,499	ebay.com
2.		Ricoh GR III	109 mm	62 mm	33 mm	257 g	200	n	Feb 2019	899	amazon.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 5DS	152 mm	116 mm	76 mm	930 g	700	Y	Feb 2015	3,699	ebay.com
5.		Canon 5DS R	152 mm	116 mm	76 mm	930 g	700	Y	Feb 2015	3,699	ebay.com
6.		Fujifilm XF10	113 mm	64 mm	41 mm	279 g	330	n	Jul 2018	499	ebay.com
7.		Hasselblad X1D	150 mm	98 mm	71 mm	725 g	..	Y	Jun 2016	8,995	ebay.com
8.		Leica M11	139 mm	80 mm	39 mm	640 g	700	Y	Jan 2022	8,995	amazon.com
9.		Leica SL	147 mm	104 mm	39 mm	847 g	400	Y	Oct 2015	7,450	ebay.com
10.		Nikon D4S	160 mm	157 mm	91 mm	1350 g	3020	Y	Feb 2014	6,499	ebay.com
11.		Nikon D5	160 mm	159 mm	92 mm	1415 g	3780	Y	Jan 2016	6,499	ebay.com
12.		Nikon D7200	136 mm	107 mm	76 mm	765 g	1110	Y	Mar 2015	1,199	ebay.com
13.		Panasonic ZS200	111 mm	65 mm	45 mm	340 g	370	n	Feb 2018	799	amazon.com
14.		Pentax 645D	156 mm	117 mm	119 mm	1480 g	800	Y	Mar 2010	9,995	ebay.com
15.		Ricoh GR	117 mm	61 mm	35 mm	245 g	290	n	Apr 2013	799	ebay.com
16.		Ricoh GR II	117 mm	63 mm	35 mm	251 g	320	n	Jun 2015	699	ebay.com
17.		Ricoh GR IIIx	109 mm	62 mm	35 mm	262 g	200	n	Sep 2021	999	amazon.com
Note: Measurements and pricing do not include easily detachable parts, such as add-on or interchangeable lenses or optional viewfinders.
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Any camera decision will naturally be influenced heavily by the price. The retail prices at the time of the camera’s release place the model in the market relative to other models in the producer’s line-up and the competition. The GR III was launched at a lower price than the 645Z, despite having a lens built in. 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 645Z features a medium format sensor and the Ricoh GR III an APS-C sensor. The sensor area in the GR III is 74 percent smaller. As a result of these sensor size differences, the cameras have a format factor of, respectively, 0.79 and 1.5. The sensor in the 645Z has a native 4:3 aspect ratio, while the one in the GR III offers a 3:2 aspect.

With 51.1MP, the 645Z offers a higher resolution than the GR III (24MP), but the 645Z nevertheless has larger individual pixels (pixel pitch of 5.30μm versus 3.91μm for the GR III) due to its larger sensor. However, the GR III is a much more recent model (by 4 years and 10 months) than the 645Z, 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 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 Ricoh GR III are 30 x 20 inches or 76.2 x 50.8 cm for good quality, 24 x 16 inches or 61 x 40.6 cm for very good quality, and 20 x 13.3 inches or 50.8 x 33.9 cm for excellent quality prints.

The GR III has on-sensor phase detect pixels, which results in fast and reliable autofocus acquisition even during live view operation.

The Pentax 645Z has a native sensitivity range from ISO 100 to ISO 204800. The corresponding ISO settings for the Ricoh GR III are ISO 100 to ISO 102400 (no boost).

Technology-wise, both cameras are equipped with CMOS (Complementary Metal–Oxide–Semiconductor) sensors. 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. 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 645Z	Medium Format	51.1	8256	6192	1080/60i	26.0	14.7	4505	101
2.		Ricoh GR III	APS-C	24.0	6000	4000	1080/60p	24.1	13.5	1897	83
3.		Canon 1D X Mark II	Full Frame	20.0	5472	3648	4K/60p	24.1	13.5	3207	88
4.		Canon 5DS	Full Frame	50.3	8688	5792	1080/30p	24.7	12.4	2381	87
5.		Canon 5DS R	Full Frame	50.3	8688	5792	1080/30p	24.6	12.4	2308	86
6.		Fujifilm XF10	APS-C	24.0	6000	4000	4K/15p	24.0	13.4	1844	83
7.		Hasselblad X1D	Medium Format	51.3	8272	6200	1080/25p	26.2	14.8	4489	102
8.		Leica M11	Full Frame	60.3	9528	6328	none	26.3	14.8	3376	100
9.		Leica SL	Full Frame	24.0	6000	4000	4K/30p	25.0	13.4	1821	88
10.		Nikon D4S	Full Frame	16.2	4928	3280	1080/60p	24.4	13.3	3074	89
11.		Nikon D5	Full Frame	20.7	5588	3712	4K/30p	25.1	12.3	2343	88
12.		Nikon D7200	APS-C	24.0	6000	4000	1080/60p	24.5	14.6	1333	87
13.		Panasonic ZS200	1-inch	20.0	5472	3648	4K/30p	22.0	12.2	449	64
14.		Pentax 645D	Medium Format	39.5	7264	5440	none	24.6	12.6	1262	82
15.		Ricoh GR	APS-C	16.1	4928	3264	1080/30p	23.6	13.5	972	78
16.		Ricoh GR II	APS-C	16.1	4928	3264	1080/30p	23.6	13.7	1078	80
17.		Ricoh GR IIIx	APS-C	24.0	6000	4000	1080/60p	24.2	13.8	2146	85
Note: DXO values in italics represent estimates based on sensor size and age.

Many modern cameras are not only capable of taking still images, but also of capturing video footage. Both cameras under consideration have a sensor with sufficiently fast read-out times for moving pictures, but the GR III provides a faster frame rate than the 645Z. It can shoot movie footage at 1080/60p, 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 645Z has an optical viewfinder, which can be very useful when shooting in bright sunlight. In contrast, the GR III relies on live view and the rear LCD for framing. That said, the GR III can be equipped with an optional viewfinder – the GV-1. The adjacent table lists some of the other core features of the Pentax 645Z and Ricoh GR III 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 645Z	optical	Y	3.2 / 1037	tilting	n	1/4000s	3.0/s	n	n
2.		Ricoh GR III	optional	n	3.0 / 1037	fixed	Y	1/4000s	4.0/s	n	Y
3.		Canon 1D X Mark II	optical	Y	3.2 / 1620	fixed	Y	1/8000s	16.0/s	n	n
4.		Canon 5DS	optical	Y	3.2 / 1040	fixed	n	1/8000s	5.0/s	n	n
5.		Canon 5DS R	optical	Y	3.2 / 1040	fixed	n	1/8000s	5.0/s	n	n
6.		Fujifilm XF10	none	n	3.0 / 1040	fixed	Y	1/4000s	6.0/s	Y	n
7.		Hasselblad X1D	2360	n	3.0 / 920	fixed	Y	1/2000s	2.3/s	n	n
8.		Leica M11	optical	n	3.0 / 2333	fixed	Y	1/4000s	4.5/s	n	n
9.		Leica SL	4400	Y	3.0 / 1040	fixed	Y	1/8000s	11.0/s	n	n
10.		Nikon D4S	optical	Y	3.2 / 921	fixed	n	1/8000s	11.0/s	n	n
11.		Nikon D5	optical	Y	3.2 / 2359	fixed	Y	1/8000s	14.0/s	n	n
12.		Nikon D7200	optical	Y	3.2 / 1229	fixed	n	1/8000s	6.0/s	Y	n
13.		Panasonic ZS200	2330	n	3.0 / 1240	fixed	Y	1/2000s	10.0/s	Y	Y
14.		Pentax 645D	optical	Y	3.0 / 921	fixed	n	1/4000s	1.1/s	n	n
15.		Ricoh GR	optional	n	3.0 / 1230	fixed	n	1/4000s	4.0/s	Y	n
16.		Ricoh GR II	optional	n	3.0 / 1230	fixed	n	1/4000s	4.0/s	Y	n
17.		Ricoh GR IIIx	optional	n	3.0 / 1037	fixed	Y	1/4000s	4.0/s	n	Y
Note: *) Information refers to the mechanical shutter, unless the camera only has an electronic one.

One feature that is present on the 645Z, but is missing on the GR III 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 645Z and the Ricoh GR III both have 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.

Concerning the storage of imaging data, both the 645Z and the GR III write their files to SDXC cards. The 645Z features dual card slots, which can be very useful in case a memory card fails. In contrast, the GR III 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 Ricoh GR III 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 645Z	Y	stereo / mono	Y	-	mini	3.0	-	-	-
2.		Ricoh GR III	Y	stereo / mono	-	-	-	3.0	Y	-	Y
3.		Canon 1D X Mark II	Y	mono / mono	Y	Y	mini	3.0	-	-	-
4.		Canon 5DS	Y	mono / mono	Y	-	mini	3.0	-	-	-
5.		Canon 5DS R	Y	mono / mono	Y	-	mini	3.0	-	-	-
6.		Fujifilm XF10	-	stereo / mono	Y	-	micro	2.0	Y	-	Y
7.		Hasselblad X1D	Y	stereo / mono	Y	Y	mini	3.0	Y	-	-
8.		Leica M11	Y	- / -	-	-	-	3.2	Y	-	Y
9.		Leica SL	Y	stereo / mono	Y	Y	full	3.0	Y	-	-
10.		Nikon D4S	Y	mono / mono	Y	Y	mini	2.0	-	-	-
11.		Nikon D5	Y	stereo / mono	Y	Y	mini	3.0	-	-	-
12.		Nikon D7200	Y	stereo / mono	Y	Y	mini	2.0	Y	Y	-
13.		Panasonic ZS200	-	stereo / mono	-	-	micro	2.0	Y	-	Y
14.		Pentax 645D	Y	stereo / -	-	-	-	2.0	-	-	-
15.		Ricoh GR	Y	mono / mono	-	-	micro	2.0	-	-	-
16.		Ricoh GR II	Y	stereo / mono	-	-	micro	2.0	Y	Y	-
17.		Ricoh GR IIIx	Y	stereo / mono	-	-	-	3.0	Y	-	Y

It is notable that the 645Z has a microphone port, which is missing on the GR III. Such an external microphone input can help to substantially improve the quality of audio recordings when a good external microphone is used.

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

The GR III is a recent model that features in the current product line-up of Ricoh. In contrast, the 645Z has been discontinued (but can be found pre-owned on ebay). There has not been a direct replacement model for the 645Z from Pentax. Further information on the features and operation of the 645Z and GR III can be found, respectively, in the Pentax 645Z Manual (free pdf) or the online Ricoh GR III Manual.

Review summary

So what conclusions can be drawn? Is the Pentax 645Z better than the Ricoh GR III or vice versa? Below is a summary of the relative strengths of each of the two contestants.

Advantages of the Pentax 645Z:

• More detail: Offers more megapixels (51.1 vs 24MP) with a 43% higher linear resolution.
• Better sound: Can connect to an external microphone for higher quality sound recording.
• Easier framing: Has an optical viewfinder for image composition and settings control.
• 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.
• More flexible LCD: Has a tilting screen for odd-angle shots in landscape orientation.
• More flexible: Can take a variety of interchangeable lenses, including specialty optics.
• Longer lasting: Can take more shots (650 versus 200) on a single battery charge.
• Better sealing: Is weather sealed to enable shooting in dusty or wet environments.
• 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 April 2014).

Arguments in favor of the Ricoh GR III:

• Better video: Provides higher movie framerates (1080/60p versus 1080/60i).
• Better live-view autofocus: Features on-sensor phase-detection for more confident autofocus.
• Fewer buttons to press: Has a touchscreen to facilitate handling and shooting adjustments.
• Faster burst: Shoots at higher frequency (4 vs 3 flaps/sec) to capture the decisive moment.
• Ready to shoot: Comes with an integrated lens, while the 645Z requires a separate lens.
• More compact: Is smaller (109x62mm vs 156x117mm) and will fit more readily into a bag.
• Less heavy: Has a lower weight even though it has a lens built in (unlike the 645Z).
• 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.
• Easier file upload: Has wifi built in for automatic backup or image transfer to the web.
• Easier wireless transfer: Supports Bluetooth for image sharing without cables.
• More affordable: Was introduced at a lower price, despite coming with a built-in lens.
• More modern: Reflects 4 years and 10 months of technical progress since the 645Z launch.

If the count of individual advantages (bullet points above) is taken as a guide, the GR III comes out slightly ahead of the 645Z (13 : 12 points). However, the pertinence of the various camera strengths will differ across photographers, so that you might want to weigh individual camera traits according to their importance for your own imaging needs before making a camera decision. 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 Ricoh GR III place the cameras among the top in their class? Find out in the latest Best DSLR Camera and Best Prime Lens Compact 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 GR III in practical situations. User reviews, such as those found at amazon, can sometimes inform about these issues, but such feedback is often incomplete, inconsistent, and biased.

Expert reviews

This is why hands-on reviews by experts are important. The table below provides a synthesis of the camera assessments of some of the best known photo-gear 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 645Z	5/5	..	3.5/5	..	4.5/5	5/5	Apr 2014	8,499	ebay.com
2.		Ricoh GR III	4/5	..	3.5/5	81/100	4/5	..	Feb 2019	899	amazon.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 5DS	..	+	..	83/100	4.5/5	4.5/5	Feb 2015	3,699	ebay.com
5.		Canon 5DS R	5/5	+	..	83/100	5/5	4.5/5	Feb 2015	3,699	ebay.com
6.		Fujifilm XF10	..	..	4/5	75/100	4/5	4.5/5	Jul 2018	499	ebay.com
7.		Hasselblad X1D	..	o	..	81/100	..	4/5	Jun 2016	8,995	ebay.com
8.		Leica M11	4.5/5	..	4.5/5	..	4.5/5	4.5/5	Jan 2022	8,995	amazon.com
9.		Leica SL	4/5	..	4/5	84/100	4.5/5	4/5	Oct 2015	7,450	ebay.com
10.		Nikon D4S	5/5	..	..	..	4.5/5	4.5/5	Feb 2014	6,499	ebay.com
11.		Nikon D5	..	..	4/5	89/100	4.5/5	5/5	Jan 2016	6,499	ebay.com
12.		Nikon D7200	4/5	+ +	..	84/100	4.5/5	4.5/5	Mar 2015	1,199	ebay.com
13.		Panasonic ZS200	..	+ +	4.5/5	81/100	4.5/5	4.5/5	Feb 2018	799	amazon.com
14.		Pentax 645D	5/5	..	..	..	..	..	Mar 2010	9,995	ebay.com
15.		Ricoh GR	5/5	..	..	79/100	4.5/5	4.5/5	Apr 2013	799	ebay.com
16.		Ricoh GR II	..	..	..	..	4.5/5	4.5/5	Jun 2015	699	ebay.com
17.		Ricoh GR IIIx	..	..	4.5/5	..	..	..	Sep 2021	999	amazon.com
Note: (+ +) 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. It should also be noted that some of the review sites have over time altered the way they render their verdicts.

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Other camera comparisons

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