Panasonic GX9 vs Pentax K-S1

The Panasonic Lumix DC-GX9 and the Pentax K-S1 are two digital cameras that were announced, respectively, in February 2018 and August 2014. The GX9 is a mirrorless interchangeable lens camera, while the K-S1 is a DSLR. The cameras are based on a Four Thirds (GX9) and an APS-C (K-S1) sensor. The Panasonic has a resolution of 20.2 megapixels, whereas the Pentax provides 20 MP.

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

Headline Specifications

Panasonic GX9		Pentax K-S1
Mirrorless system camera		Digital single lens reflex
Micro Four Thirds lenses		Pentax K mount lenses
20.2 MP – Four Thirds sensor		20 MP – APS-C sensor
4K/30p Video		1080/30p Video
ISO 200-25,600		ISO 100-51,200
Electronic viewfinder (2760k dots)		Optical viewfinder
3.0" LCD – 1240k dots		3.0" LCD – 921k dots
Tilting touchscreen		Fixed screen (not touch-sensitive)
9 shutter flaps per second		5.4 shutter flaps per second
In-body stabilization		In-body stabilization
260 shots per battery charge		410 shots per battery charge
124 x 72 x 47 mm, 407 g		121 x 93 x 70 mm, 558 g

Check GX9 offers at
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Check K-S1 offers at
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Going beyond this snapshot of core features and characteristics, what are the differences between the Panasonic Lumix DC-GX9 and the Pentax K-S1? 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 Panasonic GX9 and the Pentax K-S1 is provided 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.

The GX9 can be obtained in two different colors (black, silver), while the K-S1 is available in four color-versions (black, grey, orange, white).

If the front view area (width x height) of the cameras is taken as an aggregate measure of their size, the Pentax K-S1 is notably larger (26 percent) than the Panasonic GX9. Moreover, the K-S1 is substantially heavier (37 percent) than the GX9. In this context, it is worth noting that neither the GX9 nor the K-S1 are weather-sealed.

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 GX9 gets 260 shots out of its Panasonic DMW-BLG10 battery, while the K-S1 can take 410 images on a single charge of its Pentax D-LI109 power pack. The power pack in the GX9 can be charged via the USB port, so that it is not always necessary to take the battery charger along when travelling.

The following table provides a synthesis of the main physical specifications of the two cameras and other similar ones. If you would like to visualize and compare a different camera combination, you can navigate to the CAM-parator app and make your selection from a broad list of cameras 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.		Panasonic GX9	124 mm	72 mm	47 mm	407 g	260	n	Feb 2018	849	ebay.com
2.		Pentax K-S1	121 mm	93 mm	70 mm	558 g	410	n	Aug 2014	749	ebay.com
3.		Nikon D5300	125 mm	98 mm	76 mm	480 g	600	n	Oct 2013	799	ebay.com
4.		Nikon D5500	124 mm	97 mm	70 mm	470 g	820	n	Jan 2015	899	ebay.com
5.		Olympus E-M10 II	120 mm	83 mm	47 mm	390 g	320	n	Aug 2015	649	ebay.com
6.		Olympus E-M10 III	122 mm	84 mm	50 mm	410 g	330	n	Aug 2017	649	ebay.com
7.		Olympus E-M10 IV	122 mm	84 mm	49 mm	383 g	360	n	Aug 2020	699	amazon.com
8.		Olympus E-P7	118 mm	69 mm	38 mm	337 g	360	n	Jun 2021	799	amazon.com
9.		Panasonic G95	130 mm	94 mm	77 mm	536 g	290	Y	Apr 2019	999	ebay.com
10.		Panasonic GX7	123 mm	71 mm	55 mm	402 g	350	n	Aug 2013	999	ebay.com
11.		Panasonic GX8	133 mm	78 mm	63 mm	487 g	330	Y	Jul 2015	1,199	ebay.com
12.		Panasonic GX85	122 mm	71 mm	44 mm	426 g	290	n	Apr 2016	799	amazon.com
13.		Panasonic LX100 II	115 mm	66 mm	65 mm	392 g	300	n	Aug 2018	999	ebay.com
14.		Panasonic ZS200	111 mm	65 mm	45 mm	340 g	370	n	Feb 2018	799	amazon.com
15.		Pentax K-500	130 mm	97 mm	71 mm	646 g	710	n	Jun 2013	549	ebay.com
16.		Pentax K-S2	123 mm	91 mm	73 mm	678 g	410	Y	Feb 2015	749	ebay.com
17.		Sony A68	143 mm	104 mm	81 mm	610 g	540	n	Nov 2015	699	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 K-S1 was launched at a somewhat lower price (by 12 percent) than the GX9, which makes it more attractive for photographers on a tight budget. 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. 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 Panasonic GX9 features a Four Thirds sensor and the Pentax K-S1 an APS-C sensor. The sensor area in the K-S1 is 63 percent bigger. As a result of these sensor size differences, the cameras have a format factor of, respectively, 2.0 and 1.5. The sensor in the GX9 has a native 4:3 aspect ratio, while the one in the K-S1 offers a 3:2 aspect.

Despite having a smaller sensor, the Panasonic GX9 offers a higher resolution of 20.2 megapixels, compared with 20 MP of the Pentax K-S1. This megapixels advantage comes at the cost of a higher pixel density and a smaller size of the individual pixel (with a pixel pitch of 3.34μm versus 4.28μm for the K-S1). However, it should be noted that the GX9 is much more recent (by 3 years and 5 months) than the K-S1, 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.

The Panasonic Lumix DC-GX9 has a native sensitivity range from ISO 200 to ISO 25600, which can be extended to ISO 100-25600. The corresponding ISO settings for the Pentax K-S1 are ISO 100 to ISO 51200 (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 is based on lab testing and assigns an overall score to each camera sensor, as well as ratings for dynamic range ("DXO Landscape"), color depth ("DXO Portrait"), and low-light sensitivity ("DXO Sports"). 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.		Panasonic GX9	Four Thirds	20.2	5184	3888	4K/30p	23.1	12.8	1163	74
2.		Pentax K-S1	APS-C	20.0	5472	3648	1080/30p	23.5	13.0	1061	78
3.		Nikon D5300	APS-C	24.0	6000	4000	1080/60p	24.0	13.9	1338	83
4.		Nikon D5500	APS-C	24.0	6000	4000	1080/60p	24.1	14.0	1438	84
5.		Olympus E-M10 II	Four Thirds	15.9	4608	3456	1080/60p	23.1	12.5	842	73
6.		Olympus E-M10 III	Four Thirds	15.9	4608	3456	4K/30p	23.1	12.8	1120	74
7.		Olympus E-M10 IV	Four Thirds	20.2	5184	3888	4K/30p	23.3	13.2	1402	76
8.		Olympus E-P7	Four Thirds	20.2	5184	3888	4K/30p	23.4	13.3	1494	77
9.		Panasonic G95	Four Thirds	20.2	5184	3888	4K/30p	23.2	13.0	1273	75
10.		Panasonic GX7	Four Thirds	15.8	4592	3448	1080/60p	22.6	12.2	718	70
11.		Panasonic GX8	Four Thirds	20.2	5184	3888	4K/30p	23.5	12.6	806	75
12.		Panasonic GX85	Four Thirds	15.8	4592	3448	4K/30p	22.9	12.6	662	71
13.		Panasonic LX100 II	Four Thirds	16.8	4736	3552	4K/30p	22.8	12.7	979	72
14.		Panasonic ZS200	1-inch	20.0	5472	3648	4K/30p	22.0	12.2	449	64
15.		Pentax K-500	APS-C	16.1	4928	3264	1080/30p	23.7	13.1	1087	79
16.		Pentax K-S2	APS-C	20.0	5472	3648	1080/30p	23.6	12.9	1514	79
17.		Sony A68	APS-C	24.0	6000	4000	1080/60i	24.1	13.5	701	79
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 can also record movies. The two cameras under consideration both have sensors whose read-out speed is fast enough to capture moving pictures, but the GX9 provides a higher video resolution than the K-S1. It can shoot video footage at 4K/30p, while the Pentax is limited to 1080/30p.

Feature comparison

Beyond body and sensor, cameras can and do differ across a range of features. For example, the GX9 has an electronic viewfinder (2760k dots), while the K-S1 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 field of view (100%), but the viewfinder of the GX9 has a higher magnification than the one of the K-S1 (0.70x vs 0.63x), 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 Panasonic GX9 and Pentax K-S1 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.		Panasonic GX9	2760	n	3.0 / 1240	tilting	Y	1/4000s	9.0/s	Y	Y
2.		Pentax K-S1	optical	n	3.0 / 921	fixed	n	1/6000s	5.4/s	Y	Y
3.		Nikon D5300	optical	n	3.2 / 1037	swivel	n	1/4000s	5.0/s	Y	n
4.		Nikon D5500	optical	n	3.2 / 1037	swivel	Y	1/4000s	5.0/s	Y	n
5.		Olympus E-M10 II	2360	n	3.0 / 1040	tilting	Y	1/4000s	8.0/s	Y	Y
6.		Olympus E-M10 III	2360	n	3.0 / 1040	tilting	Y	1/4000s	8.6/s	Y	Y
7.		Olympus E-M10 IV	2360	n	3.0 / 1040	tilting	Y	1/4000s	15.0/s	Y	Y
8.		Olympus E-P7	none	n	3.0 / 1040	tilting	Y	1/4000s	8.7/s	Y	Y
9.		Panasonic G95	2360	n	3.0 / 1240	swivel	Y	1/4000s	9.0/s	Y	Y
10.		Panasonic GX7	2760	n	3.0 / 1040	tilting	Y	1/8000s	5.0/s	Y	Y
11.		Panasonic GX8	2360	n	3.0 / 1040	swivel	Y	1/8000s	10.0/s	n	Y
12.		Panasonic GX85	2765	n	3.0 / 1040	tilting	Y	1/4000s	8.0/s	Y	Y
13.		Panasonic LX100 II	2764	n	3.0 / 1240	fixed	Y	1/4000s	11.0/s	n	Y
14.		Panasonic ZS200	2330	n	3.0 / 1240	fixed	Y	1/2000s	10.0/s	Y	Y
15.		Pentax K-500	optical	n	3.0 / 921	fixed	n	1/6000s	6.0/s	Y	Y
16.		Pentax K-S2	optical	n	3.0 / 921	swivel	n	1/6000s	5.4/s	Y	Y
17.		Sony A68	1440	Y	2.7 / 460	tilting	n	1/4000s	8.0/s	Y	Y
Note: *) Information refers to the mechanical shutter, unless the camera only has an electronic one.

One differentiating feature between the two cameras concerns the touch sensitivity of the rear screen. The GX9 has a touchscreen, while the K-S1 has a conventional panel. Touch control can be particularly helpful, for example, for setting the focus point.

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 GX9 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 Panasonic GX9 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 GX9 and the K-S1 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 Panasonic Lumix DC-GX9 and Pentax K-S1 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.		Panasonic GX9	Y	stereo / mono	-	-	micro	2.0	Y	-	Y
2.		Pentax K-S1	Y	stereo / mono	-	-	micro	2.0	-	-	-
3.		Nikon D5300	Y	stereo / mono	Y	-	mini	2.0	Y	-	-
4.		Nikon D5500	Y	stereo / mono	Y	-	mini	2.0	Y	-	-
5.		Olympus E-M10 II	Y	stereo / mono	-	-	micro	2.0	Y	-	-
6.		Olympus E-M10 III	Y	stereo / mono	-	-	micro	2.0	Y	-	-
7.		Olympus E-M10 IV	Y	stereo / mono	-	-	micro	2.0	Y	-	Y
8.		Olympus E-P7	Y	stereo / mono	-	-	micro	2.0	Y	-	Y
9.		Panasonic G95	Y	stereo / mono	Y	Y	micro	2.0	Y	-	Y
10.		Panasonic GX7	Y	stereo / mono	-	-	mini	2.0	Y	Y	-
11.		Panasonic GX8	Y	stereo / mono	Y	-	micro	2.0	Y	Y	-
12.		Panasonic GX85	Y	stereo / mono	-	-	micro	2.0	Y	-	-
13.		Panasonic LX100 II	Y	stereo / mono	-	-	micro	2.0	Y	-	Y
14.		Panasonic ZS200	-	stereo / mono	-	-	micro	2.0	Y	-	Y
15.		Pentax K-500	Y	mono / mono	-	-	-	2.0	-	-	-
16.		Pentax K-S2	Y	mono / mono	Y	-	micro	2.0	Y	Y	-
17.		Sony A68	Y	stereo / mono	Y	-	micro	2.0	-	-	-

It is notable that the GX9 offers wifi support, while the K-S1 does not. Wifi can be a very convenient means to transfer image data to an off-camera location.

Both the GX9 and the K-S1 have been discontinued, but can regularly be found used on ebay. The K-S1 was replaced by the Pentax K-S2, while the GX9 does not have a direct successor. Further information on the features and operation of the GX9 and K-S1 can be found, respectively, in the Panasonic GX9 Manual (free pdf) or the online Pentax K-S1 Manual.

Review summary

So what conclusions can be drawn? Is the Panasonic GX9 better than the Pentax K-S1 or vice versa? The listing below highlights the relative strengths of the two models.

Arguments in favor of the Panasonic Lumix DC-GX9:

• Better video: Provides higher definition movie capture (4K/30p vs 1080/30p).
• More framing info: Has an electronic viewfinder that displays shooting data.
• Larger viewfinder image: Features a viewfinder with a higher magnification (0.70x vs 0.63x).
• More detailed LCD: Has a higher resolution rear screen (1240k vs 921k dots).
• More flexible LCD: Has a tilting screen for odd-angle shots in landscape orientation.
• Fewer buttons to press: Is equipped with a touch-sensitive rear screen to facilitate handling.
• Faster burst: Shoots at higher frequency (9 vs 5.4 flaps/sec) to capture the decisive moment.
• Less disturbing: Has an electronic shutter option for completely silent shooting.
• Easier time-lapse photography: Has an intervalometer built-in for low frequency shooting.
• More compact: Is smaller (124x72mm vs 121x93mm) and thus needs less room in the bag.
• Less heavy: Is lighter (by 151g or 27 percent) and hence easier to carry around.
• Easier travel charging: Can be conveniently charged via its USB port.
• More legacy lens friendly: Can take a broad range of non-native lenses via adapters.
• 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 3 years and 5 months of technical progress since the K-S1 launch.

Advantages of the Pentax K-S1:

• Brighter framing: Features an optical viewfinder for clear, lag-free composition.
• Faster shutter: Has higher mechanical shutter speed (1/6000s vs 1/4000s) to freeze action.
• Longer lasting: Gets more shots (410 versus 260) out of a single battery charge.
• More affordable: Was released into a lower priced segment (12 percent cheaper at launch).
• More heavily discounted: Has been around for much longer (launched in August 2014).

If the count of relative strengths (bullet points above) is taken as a measure, the GX9 is the clear winner of the match-up (16 : 5 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 wildlife photographer will view the differences between cameras in a way that diverges from the perspective of a family photog, and a person interested in architecture has distinct needs from a sports 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 Panasonic GX9 and the Pentax K-S1 place the cameras among the top in their class? Find out in the latest Best Mirrorless Interchangeable Lens Camera and Best DSLR Camera listings whether the two cameras rank among the cream of the crop.

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 shooting experience and imaging performance when actually working with the GX9 or the K-S1. User reviews that are available, for instance, at amazon can sometimes shed light on these issues, but such feedback is all too often partial, inconsistent, and inaccurate.

Expert reviews

This is why expert reviews are important. 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.		Panasonic GX9	4/5	+	4/5	84/100	4.5/5	4.5/5	Feb 2018	849	ebay.com
2.		Pentax K-S1	4/5	..	..	..	4.5/5	4/5	Aug 2014	749	ebay.com
3.		Nikon D5300	4/5	+ +	..	79/100	4.5/5	4.5/5	Oct 2013	799	ebay.com
4.		Nikon D5500	5/5	+	..	79/100	4.5/5	4.5/5	Jan 2015	899	ebay.com
5.		Olympus E-M10 II	4.5/5	+ +	..	80/100	5/5	5/5	Aug 2015	649	ebay.com
6.		Olympus E-M10 III	..	+	5/5	80/100	4.5/5	4.5/5	Aug 2017	649	ebay.com
7.		Olympus E-M10 IV	4.5/5	..	5/5	81/100	4.5/5	4.5/5	Aug 2020	699	amazon.com
8.		Olympus E-P7	4/5	..	4.5/5	..	..	4.5/5	Jun 2021	799	amazon.com
9.		Panasonic G95	4.5/5	+	4.5/5	83/100	4.5/5	4.5/5	Apr 2019	999	ebay.com
10.		Panasonic GX7	4/5	+	..	79/100	5/5	5/5	Aug 2013	999	ebay.com
11.		Panasonic GX8	5/5	+	..	82/100	4.5/5	4.5/5	Jul 2015	1,199	ebay.com
12.		Panasonic GX85	4.5/5	+ +	..	82/100	5/5	5/5	Apr 2016	799	amazon.com
13.		Panasonic LX100 II	4.5/5	+	4.2/5	82/100	4.5/5	4.5/5	Aug 2018	999	ebay.com
14.		Panasonic ZS200	..	+ +	4.5/5	81/100	4.5/5	4.5/5	Feb 2018	799	amazon.com
15.		Pentax K-500	..	..	..	..	4.5/5	4.5/5	Jun 2013	549	ebay.com
16.		Pentax K-S2	4.5/5	..	..	..	5/5	4.5/5	Feb 2015	749	ebay.com
17.		Sony A68	3/5	..	..	..	4/5	4/5	Nov 2015	699	ebay.com
Note: (+ +) highly recommended; (+) recommended; (o) reviewed; (..) not available.

The above review scores should be interpreted 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 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

Did this review help to inform your camera decision process? In case you are interested in seeing how other cameras pair up, just make a corresponding selection in the search boxes below. There is also a set of direct links to comparison reviews that other users of the CAM-parator app explored.

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