Pentax K-S1 vs Ricoh GR IIIx

The Pentax K-S1 and the Ricoh GR IIIx are two digital cameras that were announced, respectively, in August 2014 and September 2021. The K-S1 is a DSLR, while the GR IIIx is a fixed lens compact. Both cameras are equipped with an APS-C sensor. The Pentax has a resolution of 20 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 K-S1		Ricoh GR IIIx
Digital single lens reflex		Fixed lens compact camera
Pentax K mount lenses		40mm f/2.8
20 MP – APS-C sensor		24 MP – APS-C sensor
1080/30p Video		1080/60p Video
ISO 100-51,200		ISO 100-102,400
Optical viewfinder		Viewfinder optional
3.0" LCD – 921k dots		3.0" LCD – 1037k dots
Fixed screen (not touch-sensitive)		Fixed touchscreen
5.4 shutter flaps per second		4 shutter flaps per second
In-body stabilization		In-body stabilization
410 shots per battery charge		200 shots per battery charge
121 x 93 x 70 mm, 558 g		109 x 62 x 35 mm, 262 g

Check K-S1 offers at
ebay.com
Check GR IIIx price at
amazon.com

Going beyond this snapshot of core features and characteristics, what are the differences between the Pentax K-S1 and the Ricoh GR IIIx? 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 K-S1 and the Ricoh GR IIIx are illustrated 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 size dimensions are rounded to the nearest millimeter.

The K-S1 can be obtained in four different colors (black, grey, orange, white), while the GR IIIx is only available in black.

If the front view area (width x height) of the cameras is taken as an aggregate measure of their size, the Ricoh GR IIIx is considerably smaller (40 percent) than the Pentax K-S1. In this context, it is worth noting that neither the K-S1 nor the GR IIIx are weather-sealed.

The above size and weight comparisons are to some extent incomplete and possibly misleading, as the GR IIIx has a lens built in, whereas the K-S1 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 K-S1 gets 410 shots out of its Pentax D-LI109 battery, while the GR IIIx can take 200 images on a single charge of its Ricoh DB-110 power pack. The power pack in the GR IIIx 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. 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 K-S1	121 mm	93 mm	70 mm	558 g	410	n	Aug 2014	749	ebay.com
2.		Ricoh GR IIIx	109 mm	62 mm	35 mm	262 g	200	n	Sep 2021	999	amazon.com
3.		Fujifilm X-S10	126 mm	85 mm	65 mm	465 g	325	n	Oct 2020	999	amazon.com
4.		Nikon D5300	125 mm	98 mm	76 mm	480 g	600	n	Oct 2013	799	ebay.com
5.		Nikon D5500	124 mm	97 mm	70 mm	470 g	820	n	Jan 2015	899	ebay.com
6.		Pentax K-3	131 mm	100 mm	77 mm	800 g	560	Y	Oct 2013	1,299	ebay.com
7.		Pentax K-3 II	131 mm	100 mm	77 mm	800 g	720	Y	Apr 2015	1,099	ebay.com
8.		Pentax K-30	130 mm	97 mm	71 mm	650 g	410	Y	May 2012	849	ebay.com
9.		Pentax K-50	130 mm	97 mm	71 mm	650 g	410	Y	Jun 2013	599	ebay.com
10.		Pentax K-500	130 mm	97 mm	71 mm	646 g	710	n	Jun 2013	549	ebay.com
11.		Pentax K-S2	123 mm	91 mm	73 mm	678 g	410	Y	Feb 2015	749	ebay.com
12.		Ricoh GR II	117 mm	63 mm	35 mm	251 g	320	n	Jun 2015	699	ebay.com
13.		Ricoh GR III	109 mm	62 mm	33 mm	257 g	200	n	Feb 2019	899	amazon.com
14.		Sony A58	129 mm	95 mm	78 mm	492 g	690	n	Feb 2013	599	ebay.com
15.		Sony A68	143 mm	104 mm	81 mm	610 g	540	n	Nov 2015	699	ebay.com
16.		Sony RX100 V	102 mm	58 mm	41 mm	299 g	220	n	Oct 2016	999	ebay.com
17.		Sony RX100 VI	102 mm	58 mm	43 mm	301 g	240	n	Jun 2018	1,199	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 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. Normally, street prices remain initially close to the MSRP, but after a couple of months, the first discounts appear. 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 sensor inside a digital camera is one of the key determinants 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 tend to be more expensive and lead to bigger and heavier cameras and lenses.

Both cameras under consideration feature an APS-C sensor and have a format factor (sometimes also referred to as "crop factor") of 1.5. Within the spectrum of camera sensors, this places the review cameras among the medium-sized sensor cameras that aim to strike a balance between image quality and portability. Both cameras have a native aspect ratio (sensor width to sensor height) of 3:2.

While the two cameras under review share the same sensor size, the GR IIIx offers a higher resolution of 24 megapixels, compared with 20 MP of the K-S1. This megapixels advantage translates into a 10 percent gain in linear resolution. On the other hand, these sensor specs imply that the GR IIIx has a higher pixel density and a smaller size of the individual pixel (with a pixel pitch of 3.91μm versus 4.28μm for the K-S1). However, it should be noted that the GR IIIx is much more recent (by 7 years) than the K-S1, and its sensor will have benefitted from technological advances during this time that compensate for the smaller pixel size. 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 Ricoh GR IIIx implies greater flexibility for cropping images or the possibility to print larger pictures. The maximum print size of the GR IIIx for good quality output (200 dots per inch) amounts to 30 x 20 inches or 76.2 x 50.8 cm, for very good quality (250 dpi) 24 x 16 inches or 61 x 40.6 cm, and for excellent quality (300 dpi) 20 x 13.3 inches or 50.8 x 33.9 cm. The corresponding values for the Pentax K-S1 are 27.4 x 18.2 inches or 69.5 x 46.3 cm for good quality, 21.9 x 14.6 inches or 55.6 x 37.1 cm for very good quality, and 18.2 x 12.2 inches or 46.3 x 30.9 cm for excellent quality prints.

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

The Pentax K-S1 has a native sensitivity range from ISO 100 to ISO 51200. The corresponding ISO settings for the Ricoh GR IIIx 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.

For many cameras, data on sensor performance has been reported by DXO Mark. 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 K-S1	APS-C	20.0	5472	3648	1080/30p	23.5	13.0	1061	78
2.		Ricoh GR IIIx	APS-C	24.0	6000	4000	1080/60p	24.2	13.8	2146	85
3.		Fujifilm X-S10	APS-C	26.0	6240	4160	4K/30p	24.2	13.7	2057	85
4.		Nikon D5300	APS-C	24.0	6000	4000	1080/60p	24.0	13.9	1338	83
5.		Nikon D5500	APS-C	24.0	6000	4000	1080/60p	24.1	14.0	1438	84
6.		Pentax K-3	APS-C	24.1	6016	4000	1080/60i	23.7	13.4	1216	80
7.		Pentax K-3 II	APS-C	24.1	6016	4000	1080/60i	23.6	13.6	1106	80
8.		Pentax K-30	APS-C	16.1	4928	3264	1080/30p	23.7	13.0	1129	79
9.		Pentax K-50	APS-C	16.1	4928	3264	1080/30p	23.7	13.0	1120	79
10.		Pentax K-500	APS-C	16.1	4928	3264	1080/30p	23.7	13.1	1087	79
11.		Pentax K-S2	APS-C	20.0	5472	3648	1080/30p	23.6	12.9	1514	79
12.		Ricoh GR II	APS-C	16.1	4928	3264	1080/30p	23.6	13.7	1078	80
13.		Ricoh GR III	APS-C	24.0	6000	4000	1080/60p	24.1	13.5	1897	83
14.		Sony A58	APS-C	19.8	5456	3632	1080/60i	23.3	12.5	753	74
15.		Sony A68	APS-C	24.0	6000	4000	1080/60i	24.1	13.5	701	79
16.		Sony RX100 V	1-inch	20.0	5472	3648	4K/30p	22.8	12.4	586	70
17.		Sony RX100 VI	1-inch	20.0	5472	3648	4K/30p	22.1	12.3	478	64
Note: DXO values in italics represent estimates based on sensor size and age.

Many modern cameras cannot only take still pictures, but also record videos. Both cameras under consideration have a sensor with sufficiently fast read-out times for moving pictures, but the GR IIIx provides a faster frame rate than the K-S1. It can shoot movie footage at 1080/60p, while the Pentax is limited to 1080/30p.

Feature comparison

Apart from body and sensor, cameras can and do differ across a variety of features. For example, the K-S1 has an optical viewfinder, which can be very useful when shooting in bright sunlight. In contrast, the GR IIIx relies on live view and the rear LCD for framing. That said, the GR IIIx can be equipped with an optional viewfinder – the GV-3. The adjacent table lists some of the other core features of the Pentax K-S1 and Ricoh GR IIIx 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 K-S1	optical	n	3.0 / 921	fixed	n	1/6000s	5.4/s	Y	Y
2.		Ricoh GR IIIx	optional	n	3.0 / 1037	fixed	Y	1/4000s	4.0/s	n	Y
3.		Fujifilm X-S10	2360	n	3.0 / 1040	swivel	Y	1/4000s	8.0/s	Y	Y
4.		Nikon D5300	optical	n	3.2 / 1037	swivel	n	1/4000s	5.0/s	Y	n
5.		Nikon D5500	optical	n	3.2 / 1037	swivel	Y	1/4000s	5.0/s	Y	n
6.		Pentax K-3	optical	Y	3.2 / 1037	fixed	n	1/8000s	8.3/s	Y	Y
7.		Pentax K-3 II	optical	Y	3.2 / 1037	fixed	n	1/8000s	8.3/s	n	Y
8.		Pentax K-30	optical	n	3.0 / 921	fixed	n	1/6000s	6.0/s	Y	Y
9.		Pentax K-50	optical	n	3.0 / 921	fixed	n	1/6000s	6.0/s	Y	Y
10.		Pentax K-500	optical	n	3.0 / 921	fixed	n	1/6000s	6.0/s	Y	Y
11.		Pentax K-S2	optical	n	3.0 / 921	swivel	n	1/6000s	5.4/s	Y	Y
12.		Ricoh GR II	optional	n	3.0 / 1230	fixed	n	1/4000s	4.0/s	Y	n
13.		Ricoh GR III	optional	n	3.0 / 1037	fixed	Y	1/4000s	4.0/s	n	Y
14.		Sony A58	1440	n	2.7 / 460	tilting	n	1/4000s	5.0/s	Y	Y
15.		Sony A68	1440	Y	2.7 / 460	tilting	n	1/4000s	8.0/s	Y	Y
16.		Sony RX100 V	2359	n	3.0 / 1229	tilting	n	1/2000s	24.0/s	Y	Y
17.		Sony RX100 VI	2359	n	3.0 / 1229	tilting	Y	1/2000s	24.0/s	Y	Y
Note: *) Information refers to the mechanical shutter, unless the camera only has an electronic one.

One difference between the cameras concerns the presence of an on-board flash. The K-S1 has one, while the GR IIIx does not. While the built-in flash of the K-S1 is not very powerful, it can at times be useful as a fill-in light.

The Ricoh GR IIIx 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.

Concerning the storage of imaging data, both the K-S1 and the GR IIIx write their files to SDXC cards. 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 K-S1 and Ricoh GR IIIx 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 K-S1	Y	stereo / mono	-	-	micro	2.0	-	-	-
2.		Ricoh GR IIIx	Y	stereo / mono	-	-	-	3.0	Y	-	Y
3.		Fujifilm X-S10	Y	stereo / mono	Y	-	micro	3.2	Y	-	Y
4.		Nikon D5300	Y	stereo / mono	Y	-	mini	2.0	Y	-	-
5.		Nikon D5500	Y	stereo / mono	Y	-	mini	2.0	Y	-	-
6.		Pentax K-3	Y	mono / mono	Y	Y	mini	3.0	-	-	-
7.		Pentax K-3 II	Y	mono / mono	Y	Y	mini	3.0	-	-	-
8.		Pentax K-30	Y	mono / mono	-	-	-	2.0	-	-	-
9.		Pentax K-50	Y	mono / mono	-	-	micro	2.0	-	-	-
10.		Pentax K-500	Y	mono / mono	-	-	-	2.0	-	-	-
11.		Pentax K-S2	Y	mono / mono	Y	-	micro	2.0	Y	Y	-
12.		Ricoh GR II	Y	stereo / mono	-	-	micro	2.0	Y	Y	-
13.		Ricoh GR III	Y	stereo / mono	-	-	-	3.0	Y	-	Y
14.		Sony A58	Y	stereo / mono	Y	-	mini	2.0	-	-	-
15.		Sony A68	Y	stereo / mono	Y	-	micro	2.0	-	-	-
16.		Sony RX100 V	-	stereo / mono	-	-	micro	2.0	Y	Y	-
17.		Sony RX100 VI	-	stereo / mono	-	-	micro	2.0	Y	Y	Y

It is notable that the GR IIIx offers wifi support, which can be a very convenient means to transfer image data to an off-camera location. In contrast, the K-S1 does not provide wifi capability.

The GR IIIx is a recent model that features in the current product line-up of Ricoh. In contrast, the K-S1 has been discontinued (but can be found pre-owned on ebay). As a replacement in the same line of cameras, the K-S1 was succeeded by the Pentax K-S2. Further information on the features and operation of the K-S1 and GR IIIx can be found, respectively, in the Pentax K-S1 Manual (free pdf) or the online Ricoh GR IIIx Manual.

Review summary

So what conclusions can be drawn? Is there a clear favorite between the Pentax K-S1 and the Ricoh GR IIIx? Which camera is better? Below is a summary of the relative strengths of each of the two contestants.

Arguments in favor of the Pentax K-S1:

• Easier framing: Has an optical viewfinder for image composition and settings control.
• Faster shutter: Has higher mechanical shutter speed (1/6000s vs 1/4000s) to freeze action.
• Faster burst: Shoots at higher frequency (5.4 vs 4 flaps/sec) to capture the decisive moment.
• More flexible: Can take a variety of interchangeable lenses, including specialty optics.
• Longer lasting: Can take more shots (410 versus 200) on a single battery charge.
• Easier fill-in: Is equipped with a small onboard flash to brighten deep shadow areas.
• More heavily discounted: Has been available for much longer (launched in August 2014).

Advantages of the Ricoh GR IIIx:

• More detail: Has more megapixels (24 vs 20MP), which boosts linear resolution by 10%.
• Better video: Provides higher movie framerates (1080/60p versus 1080/30p).
• Better live-view autofocus: Features on-sensor phase-detection for more confident autofocus.
• More detailed LCD: Has a higher resolution rear screen (1037k vs 921k dots).
• Fewer buttons to press: Has a touchscreen to facilitate handling and shooting adjustments.
• Easier time-lapse photography: Has an intervalometer built-in for low frequency shooting.
• Ready to shoot: Comes with an integrated lens, while the K-S1 requires a separate lens.
• More compact: Is smaller (109x62mm vs 121x93mm) and will fit more readily into a bag.
• Less heavy: Has a lower weight even though it has a lens built in (unlike the K-S1).
• Easier travel charging: Can be conveniently charged via its USB port.
• Faster data transfer: Supports a more advanced USB protocol (3.0 vs 2.0).
• 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 modern: Reflects 7 years of technical progress since the K-S1 launch.

If the number of relative strengths (bullet points above) is taken as a guide, the GR IIIx is the clear winner of the contest (14 : 7 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 sports photographer will view the differences between cameras in a way that diverges from the perspective of a street photog, and a person interested in family portraits has distinct needs from a landscape 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 K-S1 and the Ricoh GR IIIx 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 comparison of the spec-sheets of cameras can offer a general idea of their imaging potential, it says little about, for example, the shooting experience and imaging performance of the K-S1 and the GR IIIx 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 where reviews by experts come in. The following table reports the overall ratings of the cameras as published by some of the major 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 K-S1	4/5	..	..	..	4.5/5	4/5	Aug 2014	749	ebay.com
2.		Ricoh GR IIIx	..	..	4.5/5	..	..	..	Sep 2021	999	amazon.com
3.		Fujifilm X-S10	5/5	..	4.5/5	86/100	4.5/5	4.5/5	Oct 2020	999	amazon.com
4.		Nikon D5300	4/5	+ +	..	79/100	4.5/5	4.5/5	Oct 2013	799	ebay.com
5.		Nikon D5500	5/5	+	..	79/100	4.5/5	4.5/5	Jan 2015	899	ebay.com
6.		Pentax K-3	4/5	..	..	83/100	5/5	5/5	Oct 2013	1,299	ebay.com
7.		Pentax K-3 II	4.5/5	..	..	..	5/5	5/5	Apr 2015	1,099	ebay.com
8.		Pentax K-30	4/5	..	..	78/100	4.5/5	4.5/5	May 2012	849	ebay.com
9.		Pentax K-50	5/5	..	..	..	5/5	4.5/5	Jun 2013	599	ebay.com
10.		Pentax K-500	..	..	..	..	4.5/5	4.5/5	Jun 2013	549	ebay.com
11.		Pentax K-S2	4.5/5	..	..	..	5/5	4.5/5	Feb 2015	749	ebay.com
12.		Ricoh GR II	..	..	..	..	4.5/5	4.5/5	Jun 2015	699	ebay.com
13.		Ricoh GR III	4/5	..	3.5/5	81/100	4/5	..	Feb 2019	899	amazon.com
14.		Sony A58	3/5	..	..	..	4.5/5	4.5/5	Feb 2013	599	ebay.com
15.		Sony A68	3/5	..	..	..	4/5	4/5	Nov 2015	699	ebay.com
16.		Sony RX100 V	4.5/5	+ +	..	83/100	4/5	4.5/5	Oct 2016	999	ebay.com
17.		Sony RX100 VI	4.5/5	+ +	..	83/100	4/5	4.5/5	Jun 2018	1,199	ebay.com
Note: (+ +) 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. 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.

Check K-S1 offers at
ebay.com
Check GR IIIx price at
amazon.com

Other camera comparisons

Did this review help to inform your camera decision process? If you would like to see a different side-by-side camera review, just make a corresponding selection in the search boxes below. Alternatively, you can follow any of the listed hyperlinks for comparisons that others found interesting.

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Check K-S1 offers at
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amazon.com

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