Pentax K-S1 vs Sony A6100

The Pentax K-S1 and the Sony Alpha A6100 are two digital cameras that were announced, respectively, in August 2014 and August 2019. The K-S1 is a DSLR, while the A6100 is a mirrorless interchangeable lens camera. Both cameras are equipped with an APS-C sensor. The Pentax has a resolution of 20 megapixels, whereas the Sony 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		Sony A6100
Digital single lens reflex		Mirrorless system camera
Pentax K mount lenses		Sony E mount lenses
20 MP – APS-C sensor		24 MP – APS-C sensor
1080/30p Video		4K/30p Video
ISO 100-51,200		ISO 100-32,000 (100 - 51,200)
Optical viewfinder		Electronic viewfinder (1440k dots)
3.0" LCD – 921k dots		3.0" LCD – 922k dots
Fixed screen (not touch-sensitive)		Tilting touchscreen
5.4 shutter flaps per second		11 shutter flaps per second
In-body stabilization		Lens stabilization only
410 shots per battery charge		420 shots per battery charge
121 x 93 x 70 mm, 558 g		120 x 67 x 59 mm, 396 g

Check K-S1 offers at
ebay.com
Check A6100 offers at
ebay.com

Going beyond this snapshot of core features and characteristics, what are the differences between the Pentax K-S1 and the Sony Alpha A6100? 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 Sony A6100 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.

The K-S1 can be obtained in four different colors (black, grey, orange, white), while the A6100 is available in three color-versions (black, silver, white).

If the front view area (width x height) of the cameras is taken as an aggregate measure of their size, the Sony A6100 is notably smaller (29 percent) than the Pentax K-S1. Moreover, the A6100 is markedly lighter (29 percent) than the K-S1. In this context, it is worth noting that neither the K-S1 nor the A6100 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 K-S1 gets 410 shots out of its Pentax D-LI109 battery, while the A6100 can take 420 images on a single charge of its Sony NP-FW50 power pack. The power pack in the A6100 can be charged via the USB port, which can be very convenient 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.		Pentax K-S1	121 mm	93 mm	70 mm	558 g	410	n	Aug 2014	749	ebay.com
2.		Sony A6100	120 mm	67 mm	59 mm	396 g	420	n	Aug 2019	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.		Pentax K-3	131 mm	100 mm	77 mm	800 g	560	Y	Oct 2013	1,299	ebay.com
6.		Pentax K-3 II	131 mm	100 mm	77 mm	800 g	720	Y	Apr 2015	1,099	ebay.com
7.		Pentax K-30	130 mm	97 mm	71 mm	650 g	410	Y	May 2012	849	ebay.com
8.		Pentax K-50	130 mm	97 mm	71 mm	650 g	410	Y	Jun 2013	599	ebay.com
9.		Pentax K-500	130 mm	97 mm	71 mm	646 g	710	n	Jun 2013	549	ebay.com
10.		Pentax K-S2	123 mm	91 mm	73 mm	678 g	410	Y	Feb 2015	749	ebay.com
11.		Sony A58	129 mm	95 mm	78 mm	492 g	690	n	Feb 2013	599	ebay.com
12.		Sony A68	143 mm	104 mm	81 mm	610 g	540	n	Nov 2015	699	ebay.com
13.		Sony A3000	128 mm	91 mm	85 mm	411 g	470	n	Aug 2013	329	ebay.com
14.		Sony A6000	120 mm	67 mm	45 mm	344 g	360	n	Feb 2014	599	ebay.com
15.		Sony A6400	120 mm	67 mm	50 mm	403 g	410	Y	Jan 2019	899	amazon.com
16.		Sony NEX-7	120 mm	67 mm	43 mm	400 g	430	n	Aug 2011	1,349	ebay.com
17.		Sony ZV-E10	115 mm	64 mm	45 mm	343 g	440	n	Jul 2021	699	amazon.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. The two cameras under review were launched at the same price and fall into the same 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. 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 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 A6100 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 A6100 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 A6100 is much more recent (by 5 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 the K-S1 has no anti-alias filter installed, so that it can capture all the detail its sensor resolves.

The resolution advantage of the Sony A6100 implies greater flexibility for cropping images or the possibility to print larger pictures. The maximum print size of the A6100 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 A6100 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 Sony Alpha A6100 are ISO 100 to ISO 32000, with the possibility to increase the ISO range to 100-51200.

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.		Pentax K-S1	APS-C	20.0	5472	3648	1080/30p	23.5	13.0	1061	78
2.		Sony A6100	APS-C	24.0	6000	4000	4K/30p	24.1	13.6	1947	84
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.		Pentax K-3	APS-C	24.1	6016	4000	1080/60i	23.7	13.4	1216	80
6.		Pentax K-3 II	APS-C	24.1	6016	4000	1080/60i	23.6	13.6	1106	80
7.		Pentax K-30	APS-C	16.1	4928	3264	1080/30p	23.7	13.0	1129	79
8.		Pentax K-50	APS-C	16.1	4928	3264	1080/30p	23.7	13.0	1120	79
9.		Pentax K-500	APS-C	16.1	4928	3264	1080/30p	23.7	13.1	1087	79
10.		Pentax K-S2	APS-C	20.0	5472	3648	1080/30p	23.6	12.9	1514	79
11.		Sony A58	APS-C	19.8	5456	3632	1080/60i	23.3	12.5	753	74
12.		Sony A68	APS-C	24.0	6000	4000	1080/60i	24.1	13.5	701	79
13.		Sony A3000	APS-C	19.8	5456	3632	1080/60i	23.7	12.8	1068	78
14.		Sony A6000	APS-C	24.0	6000	4000	1080/60p	24.1	13.1	1347	82
15.		Sony A6400	APS-C	24.0	6000	4000	4K/30p	24.0	13.6	1431	83
16.		Sony NEX-7	APS-C	24.0	6000	4000	1080/60i	24.1	13.4	1016	81
17.		Sony ZV-E10	APS-C	24.0	6000	4000	4K/30p	24.2	13.8	2134	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 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 A6100 provides a better video resolution than the K-S1. It can shoot movie 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 A6100 has an electronic viewfinder (1440k 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 A6100 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 Pentax K-S1 and Sony A6100 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.		Sony A6100	1440	n	3.0 / 922	tilting	Y	1/4000s	11.0/s	Y	n
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.		Pentax K-3	optical	Y	3.2 / 1037	fixed	n	1/8000s	8.3/s	Y	Y
6.		Pentax K-3 II	optical	Y	3.2 / 1037	fixed	n	1/8000s	8.3/s	n	Y
7.		Pentax K-30	optical	n	3.0 / 921	fixed	n	1/6000s	6.0/s	Y	Y
8.		Pentax K-50	optical	n	3.0 / 921	fixed	n	1/6000s	6.0/s	Y	Y
9.		Pentax K-500	optical	n	3.0 / 921	fixed	n	1/6000s	6.0/s	Y	Y
10.		Pentax K-S2	optical	n	3.0 / 921	swivel	n	1/6000s	5.4/s	Y	Y
11.		Sony A58	1440	n	2.7 / 460	tilting	n	1/4000s	5.0/s	Y	Y
12.		Sony A68	1440	Y	2.7 / 460	tilting	n	1/4000s	8.0/s	Y	Y
13.		Sony A3000	202	n	3.0 / 230	fixed	n	1/4000s	2.5/s	Y	n
14.		Sony A6000	1440	n	3.0 / 922	tilting	n	1/4000s	11.0/s	Y	n
15.		Sony A6400	2359	n	3.0 / 922	tilting	Y	1/4000s	11.0/s	Y	n
16.		Sony NEX-7	2359	n	3.0 / 921	tilting	n	1/4000s	10.0/s	Y	n
17.		Sony ZV-E10	none	n	3.0 / 922	swivel	Y	1/4000s	11.0/s	n	n
Note: *) Information refers to the mechanical shutter, unless the camera only has an electronic one.

One feature that differentiates the K-S1 and the A6100 is in-body image stabilization (IBIS). The K-S1 reduces the risk of handshake-induced blur with all attached lenses, while the A6100 offers no blur reduction with lenses that themselves do not provide optical image stabilization.

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 A6100 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 Sony A6100 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 K-S1 writes its imaging data to SDXC cards, while the A6100 uses SDXC or Memory Stick PRO Duo 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 Sony Alpha A6100 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.		Sony A6100	Y	stereo / mono	Y	-	micro	2.0	Y	Y	Y
3.		Nikon D5300	Y	stereo / mono	Y	-	mini	2.0	Y	-	-
4.		Nikon D5500	Y	stereo / mono	Y	-	mini	2.0	Y	-	-
5.		Pentax K-3	Y	mono / mono	Y	Y	mini	3.0	-	-	-
6.		Pentax K-3 II	Y	mono / mono	Y	Y	mini	3.0	-	-	-
7.		Pentax K-30	Y	mono / mono	-	-	-	2.0	-	-	-
8.		Pentax K-50	Y	mono / mono	-	-	micro	2.0	-	-	-
9.		Pentax K-500	Y	mono / mono	-	-	-	2.0	-	-	-
10.		Pentax K-S2	Y	mono / mono	Y	-	micro	2.0	Y	Y	-
11.		Sony A58	Y	stereo / mono	Y	-	mini	2.0	-	-	-
12.		Sony A68	Y	stereo / mono	Y	-	micro	2.0	-	-	-
13.		Sony A3000	Y	stereo / mono	-	-	mini	2.0	-	-	-
14.		Sony A6000	Y	stereo / mono	-	-	micro	2.0	Y	Y	-
15.		Sony A6400	Y	stereo / mono	Y	-	micro	2.0	Y	Y	Y
16.		Sony NEX-7	Y	stereo / mono	Y	-	mini	2.0	-	-	-
17.		Sony ZV-E10	Y	stereo / mono	Y	Y	micro	3.2	Y	Y	Y

It is notable that the A6100 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.

Both the K-S1 and the A6100 have been discontinued, but can regularly be found used on ebay. The K-S1 was replaced by the Pentax K-S2, while the A6100 was followed by the Sony A6600. Further information on the features and operation of the K-S1 and A6100 can be found, respectively, in the Pentax K-S1 Manual (free pdf) or the online Sony A6100 Manual.

Review summary

So what conclusions can be drawn? Is the Pentax K-S1 better than the Sony A6100 or vice versa? The listing below highlights the relative strengths of the two models.

Arguments in favor of the Pentax K-S1:

• Maximized detail: Lacks an anti-alias filter to exploit the sensor's full resolution potential.
• 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.
• Sharper images: Has hand-shake reducing image stabilization built-in.
• More heavily discounted: Has been available for much longer (launched in August 2014).

Advantages of the Sony Alpha A6100:

• More detail: Has more megapixels (24 vs 20MP), which boosts linear resolution by 10%.
• 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 1080/30p).
• Better live-view autofocus: Features on-sensor phase-detection for more confident autofocus.
• Better sound: Can connect to an external microphone for higher quality sound recording.
• 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 flexible LCD: Has a tilting screen for odd-angle shots in landscape orientation.
• Fewer buttons to press: Has a touchscreen to facilitate handling and shooting adjustments.
• More selfie-friendly: Has an articulated screen that can be turned to be front-facing.
• Faster burst: Shoots at higher frequency (11 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 (120x67mm vs 121x93mm) and will fit more readily into a bag.
• Less heavy: Has a lower weight (by 162g or 29 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.
• Easier wireless transfer: Supports Bluetooth for image sharing without cables.
• More modern: Reflects 5 years of technical progress since the K-S1 launch.

If the count of relative strengths (bullet points above) is taken as a measure, the A6100 is the clear winner of the contest (21 : 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 Pentax K-S1 and the Sony A6100 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 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 K-S1 or the A6100. 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 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 K-S1	4/5	..	..	..	4.5/5	4/5	Aug 2014	749	ebay.com
2.		Sony A6100	..	..	4/5	82/100	4/5	5/5	Aug 2019	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.		Pentax K-3	4/5	..	..	83/100	5/5	5/5	Oct 2013	1,299	ebay.com
6.		Pentax K-3 II	4.5/5	..	..	..	5/5	5/5	Apr 2015	1,099	ebay.com
7.		Pentax K-30	4/5	..	..	78/100	4.5/5	4.5/5	May 2012	849	ebay.com
8.		Pentax K-50	5/5	..	..	..	5/5	4.5/5	Jun 2013	599	ebay.com
9.		Pentax K-500	..	..	..	..	4.5/5	4.5/5	Jun 2013	549	ebay.com
10.		Pentax K-S2	4.5/5	..	..	..	5/5	4.5/5	Feb 2015	749	ebay.com
11.		Sony A58	3/5	..	..	..	4.5/5	4.5/5	Feb 2013	599	ebay.com
12.		Sony A68	3/5	..	..	..	4/5	4/5	Nov 2015	699	ebay.com
13.		Sony A3000	3/5	+	..	..	4/5	4/5	Aug 2013	329	ebay.com
14.		Sony A6000	5/5	+	4.5/5	80/100	4.5/5	5/5	Feb 2014	599	ebay.com
15.		Sony A6400	4/5	+	4/5	85/100	4.5/5	4/5	Jan 2019	899	amazon.com
16.		Sony NEX-7	5/5	+ +	..	81/100	4.5/5	5/5	Aug 2011	1,349	ebay.com
17.		Sony ZV-E10	4/5	..	4/5	82/100	4.5/5	4.5/5	Jul 2021	699	amazon.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. 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.

Check K-S1 offers at
ebay.com
Check A6100 offers at
ebay.com

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.

~

Check K-S1 offers at
ebay.com
Check A6100 offers at
ebay.com

Did you notice an error on this page? If so, please get in touch, so that we can correct the information.