Pentax K-5 vs Sony RX100

The Pentax K-5 and the Sony Cyber-shot DSC-RX100 are two digital cameras that were officially introduced, respectively, in September 2010 and June 2012. The K-5 is a DSLR, while the RX100 is a fixed lens compact. The cameras are based on an APS-C (K-5) and an one-inch (RX100) sensor. The Pentax has a resolution of 16.1 megapixels, whereas the Sony 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		Sony RX100
Digital single lens reflex		Fixed lens compact camera
Pentax K mount lenses		28-100mm f/1.8-4.9
16.1 MP – APS-C sensor		20 MP – 1" sensor
1080/25p Video		1080/60p Video
ISO 100-12,800 (80 - 51,200)		ISO 100-6,400 (100 - 25,600)
Optical viewfinder		No viewfinder, LCD framing
3.0" LCD – 921k dots		3.0" LCD – 1229k dots
Fixed screen (not touch-sensitive)		Fixed screen (not touch-sensitive)
7 shutter flaps per second		10 shutter flaps per second
In-body stabilization		Lens-based stabilization
Weathersealed body		not weather sealed
740 shots per battery charge		330 shots per battery charge
131 x 97 x 73 mm, 760 g		102 x 58 x 36 mm, 240 g

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Going beyond this snapshot of core features and characteristics, what are the differences between the Pentax K-5 and the Sony Cyber-shot DSC-RX100? 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 and the Sony RX100. 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 Sony RX100 is considerably smaller (53 percent) than the Pentax K-5. It is worth mentioning in this context that the K-5 is splash and dust resistant, while the RX100 does not feature any corresponding weather-sealing.

The above size and weight comparisons are to some extent incomplete and possibly misleading, as the RX100 has a lens built in, whereas the K-5 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-5 gets 740 shots out of its Pentax D-LI90 battery, while the RX100 can take 330 images on a single charge of its Sony NP-BX1 power pack. The power pack in the RX100 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. 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-5	131 mm	97 mm	73 mm	760 g	740	Y	Sep 2010	1,099	ebay.com
2.		Sony RX100	102 mm	58 mm	36 mm	240 g	330	n	Jun 2012	649	ebay.com
3.		Canon G9 X	98 mm	58 mm	31 mm	209 g	220	n	Oct 2015	529	ebay.com
4.		Canon G9 X Mark II	98 mm	58 mm	31 mm	206 g	235	n	Jan 2017	529	ebay.com
5.		Nikon D7000	132 mm	105 mm	77 mm	780 g	1050	Y	Sep 2010	1,499	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-5 II	131 mm	97 mm	73 mm	760 g	740	Y	Sep 2012	1,099	ebay.com
9.		Pentax K-30	130 mm	97 mm	71 mm	650 g	410	Y	May 2012	849	ebay.com
10.		Pentax K-50	130 mm	97 mm	71 mm	650 g	410	Y	Jun 2013	599	ebay.com
11.		Pentax K-70	126 mm	93 mm	74 mm	688 g	410	Y	Jun 2016	649	ebay.com
12.		Pentax K-500	130 mm	97 mm	71 mm	646 g	710	n	Jun 2013	549	ebay.com
13.		Pentax KP	132 mm	101 mm	76 mm	703 g	390	Y	Jan 2017	1,099	ebay.com
14.		Sony A77	143 mm	104 mm	81 mm	732 g	470	Y	Aug 2011	1,399	ebay.com
15.		Sony RX10	129 mm	88 mm	102 mm	813 g	420	Y	Oct 2013	1,299	ebay.com
16.		Sony RX100 II	102 mm	58 mm	38 mm	281 g	350	n	Jun 2013	749	ebay.com
17.		Sony RX100 III	102 mm	58 mm	41 mm	290 g	320	n	May 2014	799	ebay.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 listed launch prices provide an indication of the market segment that the manufacturer of the cameras have been targeting. The RX100 was launched at a lower price than the K-5, 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 size of the imaging sensor is a crucial determinant 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. Moreover, a large sensor camera will give the photographer more control over depth-of-field in the image and, thus, the ability to better isolate a subject from the background. On the downside, larger sensors are more costly to manufacture and tend to lead to bigger and heavier cameras and lenses.

Of the two cameras under consideration, the Pentax K-5 features an APS-C sensor and the Sony RX100 an one-inch sensor. The sensor area in the RX100 is 69 percent smaller. As a result of these sensor size differences, the cameras have a format factor of, respectively, 1.5 and 2.7. Both cameras have a native aspect ratio (sensor width to sensor height) of 3:2.

Despite having a smaller sensor, the RX100 offers a higher resolution of 20 megapixels, compared with 16.1 MP of the K-5. 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 2.41μm versus 4.81μm for the K-5). However, it should be noted that the RX100 is a somewhat more recent model (by 1 year and 8 months) than the K-5, and its sensor might have benefitted from technological advances during this time that partly offset its pixel-size disadvantage.

The resolution advantage of the Sony RX100 implies greater flexibility for cropping images or the possibility to print larger pictures. The maximum print size of the RX100 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 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 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 Sony Cyber-shot DSC-RX100 are ISO 100 to ISO 6400, with the possibility to increase the ISO range to 100-25600.

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 determines an overall sensor rating, as well as sub-scores for low-light sensitivity ("DXO Sports"), dynamic range ("DXO Landscape"), and color depth ("DXO Portrait"). Of the two cameras under review, the K-5 provides substantially higher image quality than the RX100, with an overall score that is 16 points higher. This advantage is based on 1.1 bits higher color depth, 1.7 EV in additional dynamic range, and 1.6 stops in additional low light sensitivity. The following table provides an overview of the physical sensor characteristics, as well as the sensor quality measurements for a selection of comparators.

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	APS-C	16.1	4928	3264	1080/25p	23.7	14.1	1162	82
2.		Sony RX100	1-inch	20.0	5472	3648	1080/60p	22.6	12.4	390	66
3.		Canon G9 X	1-inch	20.0	5472	3648	1080/60p	21.5	12.3	495	63
4.		Canon G9 X Mark II	1-inch	20.0	5472	3648	1080/60p	21.9	12.5	522	65
5.		Nikon D7000	APS-C	16.1	4928	3264	1080/24p	23.5	13.9	1167	80
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-5 II	APS-C	16.1	4928	3264	1080/25p	23.8	14.1	1235	82
9.		Pentax K-30	APS-C	16.1	4928	3264	1080/30p	23.7	13.0	1129	79
10.		Pentax K-50	APS-C	16.1	4928	3264	1080/30p	23.7	13.0	1120	79
11.		Pentax K-70	APS-C	24.0	6000	4000	1080/60i	23.8	13.1	1639	80
12.		Pentax K-500	APS-C	16.1	4928	3264	1080/30p	23.7	13.1	1087	79
13.		Pentax KP	APS-C	24.1	6016	4000	1080/60i	23.9	13.2	1699	81
14.		Sony A77	APS-C	24.0	6000	4000	1080/60p	24.0	13.2	801	78
15.		Sony RX10	1-inch	20.0	5472	3648	1080/60p	22.9	12.6	474	69
16.		Sony RX100 II	1-inch	20.0	5472	3648	1080/60p	22.5	12.4	483	67
17.		Sony RX100 III	1-inch	20.0	5472	3648	1080/60p	22.4	12.3	495	67
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 RX100 provides a faster frame rate than the K-5. It can shoot movie footage at 1080/60p, while the Pentax is limited to 1080/25p.

Feature comparison

Apart from body and sensor, cameras can and do differ across a range of features. For example, the K-5 has an optical viewfinder, which can be very useful when shooting in bright sunlight. In contrast, the RX100 relies on live view and the rear LCD for framing. The following table reports on some other key feature differences and similarities of the Pentax K-5, the Sony RX100, and comparable 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	optical	Y	3.0 / 921	fixed	n	1/8000s	7.0/s	Y	Y
2.		Sony RX100	none	n	3.0 / 1229	fixed	n	1/2000s	10.0/s	Y	Y
3.		Canon G9 X	none	n	3.0 / 1040	fixed	Y	1/2000s	6.0/s	Y	Y
4.		Canon G9 X Mark II	none	n	3.0 / 1040	fixed	Y	1/2000s	8.2/s	Y	Y
5.		Nikon D7000	optical	Y	3.0 / 921	fixed	n	1/8000s	6.0/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-5 II	optical	Y	3.0 / 921	fixed	n	1/8000s	7.0/s	Y	Y
9.		Pentax K-30	optical	n	3.0 / 921	fixed	n	1/6000s	6.0/s	Y	Y
10.		Pentax K-50	optical	n	3.0 / 921	fixed	n	1/6000s	6.0/s	Y	Y
11.		Pentax K-70	optical	n	3.0 / 921	swivel	n	1/6000s	6.0/s	Y	Y
12.		Pentax K-500	optical	n	3.0 / 921	fixed	n	1/6000s	6.0/s	Y	Y
13.		Pentax KP	optical	n	3.0 / 921	tilting	n	1/6000s	7.0/s	Y	Y
14.		Sony A77	2359	Y	3.0 / 921	full-flex	n	1/8000s	12.0/s	Y	Y
15.		Sony RX10	1440	Y	3.0 / 1229	tilting	n	1/3200s	10.0/s	Y	Y
16.		Sony RX100 II	optional	n	3.0 / 1229	tilting	n	1/2000s	10.0/s	Y	Y
17.		Sony RX100 III	1440	n	3.0 / 1229	tilting	n	1/2000s	10.0/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, but is missing on the RX100 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 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-5 writes its imaging data to SDXC cards, while the RX100 uses SDXC or Memory Stick PRO Duo 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 and Sony Cyber-shot DSC-RX100 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	Y	stereo / mono	Y	-	mini	2.0	-	-	-
2.		Sony RX100	-	stereo / mono	-	-	micro	2.0	-	-	-
3.		Canon G9 X	-	stereo / mono	-	-	micro	2.0	Y	Y	-
4.		Canon G9 X Mark II	-	stereo / mono	-	-	micro	2.0	Y	Y	Y
5.		Nikon D7000	Y	mono / mono	Y	-	mini	2.0	-	-	-
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-5 II	Y	stereo / mono	Y	-	mini	2.0	-	-	-
9.		Pentax K-30	Y	mono / mono	-	-	-	2.0	-	-	-
10.		Pentax K-50	Y	mono / mono	-	-	micro	2.0	-	-	-
11.		Pentax K-70	Y	stereo / mono	Y	-	mini	2.0	Y	-	-
12.		Pentax K-500	Y	mono / mono	-	-	-	2.0	-	-	-
13.		Pentax KP	Y	stereo / mono	Y	-	-	2.0	Y	-	-
14.		Sony A77	Y	stereo / mono	Y	-	mini	2.0	-	-	-
15.		Sony RX10	Y	stereo / mono	Y	Y	micro	2.0	Y	Y	-
16.		Sony RX100 II	Y	stereo / mono	-	-	micro	2.0	Y	Y	-
17.		Sony RX100 III	-	stereo / mono	-	-	micro	2.0	Y	Y	-

It is notable that the K-5 has a hotshoe, while the RX100 does not. This socket makes it possible to easily attach optional accessories, such as an external flash gun.

Studio photographers will appreciate that the Pentax K-5 (unlike the RX100) features a PC Sync socket, so that professional strobe lights can be controlled by the camera.

Both the K-5 and the RX100 have been discontinued, but can regularly be found used on ebay. The K-5 was replaced by the Pentax K-5 II, while the RX100 was followed by the Sony RX100 II. Further information on the features and operation of the K-5 and RX100 can be found, respectively, in the Pentax K-5 Manual (free pdf) or the online Sony RX100 Manual.

Review summary

So what conclusions can be drawn? Which of the two cameras – the Pentax K-5 or the Sony RX100 – has the upper hand? Is one clearly better than the other? Below is a summary of the relative strengths of each of the two contestants.

Reasons to prefer the Pentax K-5:

• Better image quality: Scores substantially higher (16 points) in the DXO overall assessment.
• Richer colors: Generates images with noticeably better colors (1.1 bits more color depth).
• More dynamic range: Captures a larger spectrum of light and dark details (1.7 EV of extra DR).
• Better low-light sensitivity: Requires less light for good images (1.6 stops ISO advantage).
• 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.
• Faster shutter: Has higher mechanical shutter speed (1/8000s vs 1/2000s) to freeze action.
• Easier time-lapse photography: Has an intervalometer built-in for low frequency shooting.
• More flexible: Can take a variety of interchangeable lenses, including specialty optics.
• Longer lasting: Can take more shots (740 versus 330) on a single battery charge.
• Better sealing: Is weather sealed to enable shooting in dusty or wet environments.
• Better lighting: Features a hotshoe and can thus hold and trigger an external flash gun.
• 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 2010).

Arguments in favor of the Sony Cyber-shot DSC-RX100:

• More detail: Has more megapixels (20 vs 16.1MP), which boosts linear resolution by 11%.
• Better video: Provides higher movie framerates (1080/60p versus 1080/25p).
• More detailed LCD: Has a higher resolution rear screen (1229k vs 921k dots).
• Faster burst: Shoots at higher frequency (10 vs 7 flaps/sec) to capture the decisive moment.
• Ready to shoot: Comes with an integrated lens, while the K-5 requires a separate lens.
• More compact: Is smaller (102x58mm vs 131x97mm) 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-5).
• Easier travel charging: Can be conveniently charged via its USB port.
• More affordable: Was introduced at a lower price, despite coming with a built-in lens.
• More modern: Was introduced somewhat (1 year and 8 months) more recently.

If the number of relative strengths (bullet points above) is taken as a guide, the K-5 is the clear winner of the match-up (15 : 10 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 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-5 and the Sony RX100 place the cameras among the top in their class? Find out in the latest Best DSLR Camera and Best Travel-Zoom 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 remains partial and cannot reveal, for example, the shooting experience and imaging performance when actually working with the K-5 or the RX100. 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-5	4/5	..	..	83/100	5/5	4.5/5	Sep 2010	1,099	ebay.com
2.		Sony RX100	5/5	+ +	..	78/100	4/5	5/5	Jun 2012	649	ebay.com
3.		Canon G9 X	3.5/5	+ +	..	..	4.5/5	4.5/5	Oct 2015	529	ebay.com
4.		Canon G9 X Mark II	4/5	..	4/5	75/100	4.5/5	4.5/5	Jan 2017	529	ebay.com
5.		Nikon D7000	4/5	..	..	80/100	4.5/5	4.5/5	Sep 2010	1,499	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-5 II	5/5	..	..	80/100	5/5	4.5/5	Sep 2012	1,099	ebay.com
9.		Pentax K-30	4/5	..	..	78/100	4.5/5	4.5/5	May 2012	849	ebay.com
10.		Pentax K-50	5/5	..	..	..	5/5	4.5/5	Jun 2013	599	ebay.com
11.		Pentax K-70	4.5/5	..	4/5	79/100	4.5/5	4.5/5	Jun 2016	649	ebay.com
12.		Pentax K-500	..	..	..	..	4.5/5	4.5/5	Jun 2013	549	ebay.com
13.		Pentax KP	4/5	..	3/5	82/100	5/5	4.5/5	Jan 2017	1,099	ebay.com
14.		Sony A77	5/5	91/100	..	81/100	..	5/5	Aug 2011	1,399	ebay.com
15.		Sony RX10	5/5	+	..	80/100	4.5/5	4.5/5	Oct 2013	1,299	ebay.com
16.		Sony RX100 II	5/5	+ +	..	79/100	4.5/5	4.5/5	Jun 2013	749	ebay.com
17.		Sony RX100 III	5/5	+ +	..	82/100	4.5/5	5/5	May 2014	799	ebay.com
Note: (+ +) highly recommended; (+) recommended; (o) reviewed; (..) not available.

Care should be taken when interpreting the review scores above, 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

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