Pentax K-5 II vs K-S1

The Pentax K-5 II and the Pentax K-S1 are two digital cameras that were announced, respectively, in September 2012 and August 2014. Both are DSLR (Digital Single Lens Reflex) cameras that are equipped with an APS-C sensor. The K-5 II has a resolution of 16.1 megapixels, whereas the K-S1 provides 20 MP.

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

Headline Specifications

Pentax K-5 II		Pentax K-S1
Digital single lens reflex		Digital single lens reflex
Pentax K mount lenses		Pentax K mount lenses
16.1 MP – APS-C sensor		20 MP – APS-C sensor
1080/25p Video		1080/30p Video
ISO 100-12,800 (80 - 51,200)		ISO 100-51,200
Optical viewfinder		Optical viewfinder
3.0" LCD – 921k dots		3.0" LCD – 921k dots
Fixed screen (not touch-sensitive)		Fixed screen (not touch-sensitive)
7 shutter flaps per second		5.4 shutter flaps per second
In-body stabilization		In-body stabilization
Weathersealed body		not weather sealed
740 shots per battery charge		410 shots per battery charge
131 x 97 x 73 mm, 760 g		121 x 93 x 70 mm, 558 g

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Going beyond this snapshot of core features and characteristics, what are the differences between the Pentax K-5 II 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

The side-by-side display below illustrates the physical size and weight of the Pentax K-5 II and the Pentax K-S1. 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 K-5 II 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 Pentax K-S1 is notably smaller (11 percent) than the Pentax K-5 II. Moreover, the K-S1 is markedly lighter (27 percent) than the K-5 II. It is worth mentioning in this context that the K-5 II is splash and dust resistant, while the K-S1 does not feature any corresponding weather-sealing.

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-5 II gets 740 shots out of its Pentax D-LI90 battery, while the K-S1 can take 410 images on a single charge of its Pentax D-LI109 power pack.

The table below summarizes the key physical specs of the two cameras alongside a broader set of comparators. 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	Street Price
1.		Pentax K-5 II	131 mm	97 mm	73 mm	760 g	740	Y	Sep 2012	US$ 1 099	ebay.com
2.		Pentax K-S1	121 mm	93 mm	70 mm	558 g	410	n	Aug 2014	US$ 749	ebay.com
3.		Nikon D5300	125 mm	98 mm	76 mm	480 g	600	n	Oct 2013	US$ 799	ebay.com
4.		Nikon D5500	124 mm	97 mm	70 mm	470 g	820	n	Jan 2015	US$ 899	ebay.com
5.		Nikon D7100	136 mm	107 mm	76 mm	765 g	950	Y	Feb 2013	US$ 1 199	ebay.com
6.		Olympus E-M5	122 mm	89 mm	43 mm	425 g	360	Y	Feb 2012	US$ 1 299	ebay.com
7.		Pentax K-3	131 mm	100 mm	77 mm	800 g	560	Y	Oct 2013	US$ 1 299	ebay.com
8.		Pentax K-3 II	131 mm	100 mm	77 mm	800 g	720	Y	Apr 2015	US$ 1 099	ebay.com
9.		Pentax K-5	131 mm	97 mm	73 mm	760 g	740	Y	Sep 2010	US$ 1 099	ebay.com
10.		Pentax K-30	130 mm	97 mm	71 mm	650 g	410	Y	May 2012	US$ 849	ebay.com
11.		Pentax K-50	130 mm	97 mm	71 mm	650 g	410	Y	Jun 2013	US$ 599	ebay.com
12.		Pentax K-70	126 mm	93 mm	74 mm	688 g	410	Y	Jun 2016	US$ 649	ebay.com
13.		Pentax K-500	130 mm	97 mm	71 mm	646 g	710	n	Jun 2013	US$ 549	ebay.com
14.		Pentax KP	132 mm	101 mm	76 mm	703 g	390	Y	Jan 2017	US$ 1 099	ebay.com
15.		Pentax K-S2	123 mm	91 mm	73 mm	678 g	410	Y	Feb 2015	US$ 749	ebay.com
16.		Sony A68	143 mm	104 mm	81 mm	610 g	540	n	Nov 2015	US$ 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

The price is, of course, an important factor in any camera decision. 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 markedly lower price (by 32 percent) than the K-5 II, 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 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 associated with larger, more expensive camera bodies and lenses.

Both cameras under consideration feature an APS-C sensor, but their sensors differ slightly in size. The sensor area in the K-S1 is 1 percent smaller. They nevertheless have the same format factor of 1.5. Both cameras have a native aspect ratio (sensor width to sensor height) of 3:2.

Despite having a slightly smaller sensor, the K-S1 offers a higher resolution of 20 megapixels, compared with 16.1 MP of the K-5 II. 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 4.28μm versus 4.81μm for the K-5 II). However, it should be noted that the K-S1 is a somewhat more recent model (by 1 year and 11 months) than the K-5 II, and its sensor might have benefitted from technological advances during this time that partly offset its pixel-size disadvantage. 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 Pentax K-S1 implies greater flexibility for cropping images or the possibility to print larger pictures. The maximum print size of the K-S1 for good quality output (200 dots per inch) amounts to 27.4 x 18.2 inches or 69.5 x 46.3 cm, for very good quality (250 dpi) 21.9 x 14.6 inches or 55.6 x 37.1 cm, and for excellent quality (300 dpi) 18.2 x 12.2 inches or 46.3 x 30.9 cm. The corresponding values for the Pentax K-5 II are 24.6 x 16.3 inches or 62.6 x 41.5 cm for good quality, 19.7 x 13.1 inches or 50.1 x 33.2 cm for very good quality, and 16.4 x 10.9 inches or 41.7 x 27.6 cm for excellent quality prints.

The Pentax K-5 II has a native sensitivity range from ISO 100 to ISO 12800, which can be extended to ISO 80-51200. 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 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. Of the two cameras under review, the K-5 II has a notably higher overall DXO score than the K-S1 (overall score 4 points higher), which gives it an advantage in terms of imaging quality. This advantage is based on 0.3 bits higher color depth, 1.1 EV in additional dynamic range, and 0.2 stops in additional low light sensitivity. 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-5 II	APS-C	16.1	4928	3264	1080/25p	23.8	14.1	1235	82
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.		Nikon D7100	APS-C	24.0	6000	4000	1080/60p	24.2	13.7	1256	83
6.		Olympus E-M5	Four Thirds	15.9	4608	3456	1080/60i	22.8	12.3	826	71
7.		Pentax K-3	APS-C	24.1	6016	4000	1080/60i	23.7	13.4	1216	80
8.		Pentax K-3 II	APS-C	24.1	6016	4000	1080/60i	23.6	13.6	1106	80
9.		Pentax K-5	APS-C	16.1	4928	3264	1080/25p	23.7	14.1	1162	82
10.		Pentax K-30	APS-C	16.1	4928	3264	1080/30p	23.7	13.0	1129	79
11.		Pentax K-50	APS-C	16.1	4928	3264	1080/30p	23.7	13.0	1120	79
12.		Pentax K-70	APS-C	24.0	6000	4000	1080/60i	23.8	13.1	1639	80
13.		Pentax K-500	APS-C	16.1	4928	3264	1080/30p	23.7	13.1	1087	79
14.		Pentax KP	APS-C	24.1	6016	4000	1080/60i	23.9	13.2	1699	81
15.		Pentax K-S2	APS-C	20.0	5472	3648	1080/30p	23.6	12.9	1514	79
16.		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 also of capturing video footage. Both cameras under consideration are equipped with sensors that have a sufficiently high read-out speed for moving images, but the K-S1 provides a faster frame rate than the K-5 II. It can shoot movie footage at 1080/30p, while the K-5 II is limited to 1080/25p.

Feature comparison

Apart from body and sensor, cameras can and do differ across a range of features. The K-5 II and the K-S1 are similar in the sense that both have an optical viewfinder. The latter is useful for getting a clear image for framing even in brightly lit environments. The viewfinders of both cameras offer the same field of view (100%), but the viewfinder of the K-S1 has a higher magnification than the one of the K-5 II (0.63x vs 0.61x), so that the size of the image transmitted appears closer to the size seen with the naked human eye. The table below summarizes some of the other core capabilities of the Pentax K-5 II and Pentax K-S1 in connection with corresponding information for a sample of similar cameras.

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-5 II	optical	Y	3.0 / 921	fixed	n	1/8000s	7.0/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.		Nikon D7100	optical	Y	3.2 / 1229	fixed	n	1/8000s	6.0/s	Y	n
6.		Olympus E-M5	1440	n	3.0 / 610	tilting	Y	1/4000s	9.0/s	n	Y
7.		Pentax K-3	optical	Y	3.2 / 1037	fixed	n	1/8000s	8.3/s	Y	Y
8.		Pentax K-3 II	optical	Y	3.2 / 1037	fixed	n	1/8000s	8.3/s	n	Y
9.		Pentax K-5	optical	Y	3.0 / 921	fixed	n	1/8000s	7.0/s	Y	Y
10.		Pentax K-30	optical	n	3.0 / 921	fixed	n	1/6000s	6.0/s	Y	Y
11.		Pentax K-50	optical	n	3.0 / 921	fixed	n	1/6000s	6.0/s	Y	Y
12.		Pentax K-70	optical	n	3.0 / 921	swivel	n	1/6000s	6.0/s	Y	Y
13.		Pentax K-500	optical	n	3.0 / 921	fixed	n	1/6000s	6.0/s	Y	Y
14.		Pentax KP	optical	n	3.0 / 921	tilting	n	1/6000s	7.0/s	Y	Y
15.		Pentax K-S2	optical	n	3.0 / 921	swivel	n	1/6000s	5.4/s	Y	Y
16.		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 feature that is present on the K-5 II, but is missing on the K-S1 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 K-5 II 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-5 II and the K-S1 write their files to SDXC cards. The K-S1 supports UHS-I cards (Ultra High Speed data transfer of up to 104 MB/s), while the K-5 II cannot take advantage of Ultra High Speed SD cards.

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-5 II 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.		Pentax K-5 II	Y	stereo / mono	Y	-	mini	2.0	-	-	-
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.		Nikon D7100	Y	stereo / mono	Y	Y	mini	2.0	-	-	-
6.		Olympus E-M5	Y	stereo / mono	-	-	mini	2.0	-	-	-
7.		Pentax K-3	Y	mono / mono	Y	Y	mini	3.0	-	-	-
8.		Pentax K-3 II	Y	mono / mono	Y	Y	mini	3.0	-	-	-
9.		Pentax K-5	Y	stereo / mono	Y	-	mini	2.0	-	-	-
10.		Pentax K-30	Y	mono / mono	-	-	-	2.0	-	-	-
11.		Pentax K-50	Y	mono / mono	-	-	micro	2.0	-	-	-
12.		Pentax K-70	Y	stereo / mono	Y	-	mini	2.0	Y	-	-
13.		Pentax K-500	Y	mono / mono	-	-	-	2.0	-	-	-
14.		Pentax KP	Y	stereo / mono	Y	-	-	2.0	Y	-	-
15.		Pentax K-S2	Y	mono / mono	Y	-	micro	2.0	Y	Y	-
16.		Sony A68	Y	stereo / mono	Y	-	micro	2.0	-	-	-

It is notable that the K-5 II has a microphone port, which is missing on the K-S1. 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 K-5 II (unlike the K-S1) features a PC Sync socket, so that professional strobe lights can be controlled by the camera.

Both the K-5 II and the K-S1 have been discontinued, but can regularly be found used on ebay. The K-5 II was replaced by the Pentax K-3, while the K-S1 was followed by the Pentax K-S2. Further information on the features and operation of the K-5 II and K-S1 can be found, respectively, in the Pentax K-5 II Manual (free pdf) or the online Pentax K-S1 Manual.

Review summary

So how do things add up? Is there a clear favorite between the Pentax K-5 II and the Pentax K-S1? Which camera is better? Below is a summary of the relative strengths of each of the two contestants.

Reasons to prefer the Pentax K-5 II:

• Better moiré control: Has an anti-alias filter to avoid artificial patterns to appear in images.
• Better image quality: Scores markedly higher (4 points) in the DXO overall assessment.
• More dynamic range: Captures a larger spectrum of light and dark details (1.1 EV of extra DR).
• Better sound: Can connect to an external microphone for higher quality sound recording.
• Easier setting verification: Features an LCD display on top to control shooting parameters.
• Faster shutter: Has higher mechanical shutter speed (1/8000s vs 1/6000s) to freeze action.
• Faster burst: Shoots at higher frequency (7 vs 5.4 flaps/sec) to capture the decisive moment.
• Easier time-lapse photography: Has an intervalometer built-in for low frequency shooting.
• Longer lasting: Can take more shots (740 versus 410) 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.
• More heavily discounted: Has been on the market for longer (launched in September 2012).

Advantages of the Pentax K-S1:

• More detail: Has more megapixels (20 vs 16.1MP), which boosts linear resolution by 11%.
• Maximized detail: Lacks an anti-alias filter to exploit the sensor's full resolution potential.
• Better video: Provides higher movie framerates (1080/30p versus 1080/25p).
• Larger viewfinder image: Features a viewfinder with a higher magnification (0.63x vs 0.61x).
• More compact: Is smaller (121x93mm vs 131x97mm) and will fit more readily into a bag.
• Less heavy: Has a lower weight (by 202g or 27 percent) and is thus easier to take along.
• Faster buffer clearing: Has an SD card interface that supports the UHS-I standard.
• More affordable: Was introduced into a lower priced category (32 percent cheaper at launch).
• More modern: Was introduced somewhat (1 year and 11 months) more recently.

If the count of relative strengths (bullet points above) is taken as a measure, the K-5 II emerges as the winner of the contest (12 : 9 points). However, the relative importance of the various individual camera aspects will vary according to personal preferences and needs, so that you might like to apply corresponding weights to the particular features before making a decision 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 K-5 II and the Pentax K-S1 place the cameras among the top in their class? Find out in the latest Best DSLR Camera listing 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 remains partial and cannot reveal, for example, the shooting experience and imaging performance when actually working with the K-5 II or the K-S1. 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 adjacent summary-table relays the overall verdicts of several of the most popular 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	Street Price
1.		Pentax K-5 II	5/5	..	..	80/100	5/5	4.5/5	Sep 2012	US$ 1 099	ebay.com
2.		Pentax K-S1	4/5	..	..	..	4.5/5	4/5	Aug 2014	US$ 749	ebay.com
3.		Nikon D5300	4/5	+ +	..	79/100	4.5/5	4.5/5	Oct 2013	US$ 799	ebay.com
4.		Nikon D5500	5/5	+	..	79/100	4.5/5	4.5/5	Jan 2015	US$ 899	ebay.com
5.		Nikon D7100	5/5	+ +	..	85/100	4.5/5	4.5/5	Feb 2013	US$ 1 199	ebay.com
6.		Olympus E-M5	4/5	+ +	..	80/100	4.5/5	5/5	Feb 2012	US$ 1 299	ebay.com
7.		Pentax K-3	4/5	..	..	83/100	5/5	5/5	Oct 2013	US$ 1 299	ebay.com
8.		Pentax K-3 II	4.5/5	..	..	..	5/5	5/5	Apr 2015	US$ 1 099	ebay.com
9.		Pentax K-5	4/5	..	..	83/100	5/5	4.5/5	Sep 2010	US$ 1 099	ebay.com
10.		Pentax K-30	4/5	..	..	78/100	4.5/5	4.5/5	May 2012	US$ 849	ebay.com
11.		Pentax K-50	5/5	..	..	..	5/5	4.5/5	Jun 2013	US$ 599	ebay.com
12.		Pentax K-70	4.5/5	..	4/5	79/100	4.5/5	4.5/5	Jun 2016	US$ 649	ebay.com
13.		Pentax K-500	..	..	..	..	4.5/5	4.5/5	Jun 2013	US$ 549	ebay.com
14.		Pentax KP	4/5	..	3/5	82/100	5/5	4.5/5	Jan 2017	US$ 1 099	ebay.com
15.		Pentax K-S2	4.5/5	..	..	..	5/5	4.5/5	Feb 2015	US$ 749	ebay.com
16.		Sony A68	3/5	..	..	..	4/5	4/5	Nov 2015	US$ 699	ebay.com
Note: (+ +) highly recommended; (+) recommended; (o) reviewed; (..) not available.

The review scores listed above should be treated with care, though. The assessments were made in relation to similar cameras of the same technological generation. 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. Also, please note that some of the review sites have changed their methodology and reporting over time.

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Other camera comparisons

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