Pentax K-3 III vs Sony A77

The Pentax K-3 III and the Sony Alpha SLT-A77 are two enthusiast cameras that were officially introduced, respectively, in March 2021 and August 2011. Both are DSLR (Digital Single Lens Reflex) cameras that are equipped with an APS-C sensor. The Pentax has a resolution of 25.6 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-3 III		Sony A77
Digital single lens reflex		Digital single lens reflex
Pentax K mount lenses		Sony A mount lenses
25.6 MP – APS-C sensor		24 MP – APS-C sensor
4K/30p Video		1080/60p Video
ISO 100-160,000		ISO 100-16,000 (50 - 25,600)
Optical viewfinder		Electronic viewfinder (2359k dots)
3.2" LCD – 1620k dots		3.0" LCD – 921k dots
Fixed touchscreen		Fully flexible screen (no touchscreen)
12 shutter flaps per second		12 shutter flaps per second
In-body stabilization		In-body stabilization
Weathersealed body		Weathersealed body
800 shots per battery charge		470 shots per battery charge
135 x 104 x 74 mm, 820 g		143 x 104 x 81 mm, 732 g

Check K-3 III price at
amazon.com
Check A77 offers at
ebay.com

Going beyond this snapshot of core features and characteristics, what are the differences between the Pentax K-3 III and the Sony Alpha SLT-A77? 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 Pentax K-3 III and the Sony A77 is provided in the side-by-side display below. The two cameras are presented according to their relative size. Three consecutive perspectives from the front, the top, and the back are available. All size dimensions are rounded to the nearest millimeter.

The K-3 III can be obtained in two different colors (black, silver), while the A77 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 Sony A77 is notably larger (6 percent) than the Pentax K-3 III. However, the A77 is markedly lighter (11 percent) than the K-3 III. In this context, it is worth noting that both cameras are splash and dust-proof and can, hence, be used in inclement weather conditions or harsh environments.

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-3 III gets 800 shots out of its Pentax D-LI90 battery, while the A77 can take 470 images on a single charge of its Sony NP-FM500H power pack.

The following table provides a synthesis of the main physical specifications of the two cameras and other similar ones. If you want to switch the focus of the display and review another camera pair, you can move across to the CAM-parator tool and choose from the broad selection of possible camera comparisons 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-3 III	135 mm	104 mm	74 mm	820 g	800	Y	Mar 2021	1,999	amazon.com
2.		Sony A77	143 mm	104 mm	81 mm	732 g	470	Y	Aug 2011	1,399	ebay.com
3.		Fujifilm X-H1	140 mm	97 mm	86 mm	673 g	310	Y	Feb 2018	1,899	ebay.com
4.		Fujifilm X-T4	135 mm	93 mm	64 mm	607 g	500	Y	Feb 2020	1,699	ebay.com
5.		Nikon Z6 II	134 mm	101 mm	70 mm	705 g	410	Y	Oct 2020	1,999	amazon.com
6.		Panasonic S5	133 mm	98 mm	82 mm	714 g	440	Y	Sep 2020	1,999	amazon.com
7.		Pentax K-3	131 mm	100 mm	77 mm	800 g	560	Y	Oct 2013	1,299	ebay.com
8.		Pentax K-3 II	131 mm	100 mm	77 mm	800 g	720	Y	Apr 2015	1,099	ebay.com
9.		Pentax K-5 II	131 mm	97 mm	73 mm	760 g	740	Y	Sep 2012	1,099	ebay.com
10.		Pentax K-70	126 mm	93 mm	74 mm	688 g	410	Y	Jun 2016	649	ebay.com
11.		Pentax KP	132 mm	101 mm	76 mm	703 g	390	Y	Jan 2017	1,099	ebay.com
12.		Pentax K-S2	123 mm	91 mm	73 mm	678 g	410	Y	Feb 2015	749	ebay.com
13.		Sony A7 II	127 mm	96 mm	60 mm	599 g	350	Y	Nov 2014	1,999	ebay.com
14.		Sony A77 II	143 mm	104 mm	81 mm	647 g	480	Y	May 2014	1,199	ebay.com
15.		Sony A99	147 mm	111 mm	78 mm	812 g	500	Y	Sep 2012	2,799	ebay.com
16.		Sony A6500	120 mm	67 mm	53 mm	453 g	350	Y	Oct 2016	1,399	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 naturally be influenced heavily by the price. 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 A77 was launched at a markedly lower price (by 30 percent) than the K-3 III, 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. Then, after the new model is out, very good deals can frequently be found on the pre-owned market.

Sensor comparison

The imaging sensor is at the core of digital cameras and its size is one of the main determining factors 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, but their sensors differ slightly in size. The sensor area in the A77 is 2 percent bigger. 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 Pentax K-3 III offers a higher resolution of 25.6 megapixels, compared with 24 MP of the Sony A77. 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 3.76μm versus 3.91μm for the A77). However, it should be noted that the K-3 III is much more recent (by 9 years and 7 months) than the A77, 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 the K-3 III has no anti-alias filter installed, so that it can capture all the detail its sensor resolves.

Unlike the A77, the K-3 III has the capacity to capture high quality composite images (YESMP) by combining multiple shots after shifting its sensor by miniscule distances. This multi-shot, pixel-shift mode is most suitable for photography of stationary objects (landscapes, studio scenes).

The Pentax K-3 III has a native sensitivity range from ISO 100 to ISO 160000. The corresponding ISO settings for the Sony Alpha SLT-A77 are ISO 100 to ISO 16000, with the possibility to increase the ISO range to 50-25600.

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.

For many cameras, data on sensor performance has been reported by DXO Mark. 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"). The table below summarizes the physical sensor characteristics and sensor quality findings and compares them across a set of similar 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-3 III	APS-C	25.6	6192	4128	4K/30p	24.2	13.7	2083	85
2.		Sony A77	APS-C	24.0	6000	4000	1080/60p	24.0	13.2	801	78
3.		Fujifilm X-H1	APS-C	24.0	6000	4000	4K/30p	24.0	13.3	1806	82
4.		Fujifilm X-T4	APS-C	26.0	6240	4160	4K/60p	24.1	13.6	1995	84
5.		Nikon Z6 II	Full Frame	24.3	6048	4024	4K/60p	25.0	14.4	3303	94
6.		Panasonic S5	Full Frame	24.0	6000	4000	4K/60p	25.1	14.5	2697	94
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 II	APS-C	16.1	4928	3264	1080/25p	23.8	14.1	1235	82
10.		Pentax K-70	APS-C	24.0	6000	4000	1080/60i	23.8	13.1	1639	80
11.		Pentax KP	APS-C	24.1	6016	4000	1080/60i	23.9	13.2	1699	81
12.		Pentax K-S2	APS-C	20.0	5472	3648	1080/30p	23.6	12.9	1514	79
13.		Sony A7 II	Full Frame	24.0	6000	4000	1080/60p	24.9	13.6	2449	90
14.		Sony A77 II	APS-C	24.0	6000	4000	1080/60p	24.4	13.4	1013	82
15.		Sony A99	Full Frame	24.0	6000	4000	1080/60p	25.0	14.0	1555	89
16.		Sony A6500	APS-C	24.0	6000	4000	4K/30p	24.5	13.7	1405	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 also of capturing video footage. The two cameras under consideration both have sensors whose read-out speed is fast enough to capture moving pictures, but the K-3 III provides a higher video resolution than the A77. It can shoot video footage at 4K/30p, while the Sony is limited to 1080/60p.

Feature comparison

Apart from body and sensor, cameras can and do differ across a range of features. For example, the A77 has an electronic viewfinder (2359k dots), while the K-3 III 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 A77 has a higher magnification than the one of the K-3 III (0.73x vs 0.70x), 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-3 III and Sony A77 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-3 III	optical	Y	3.2 / 1620	fixed	Y	1/8000s	12.0/s	n	Y
2.		Sony A77	2359	Y	3.0 / 921	full-flex	n	1/8000s	12.0/s	Y	Y
3.		Fujifilm X-H1	3690	Y	3.0 / 1040	full-flex	Y	1/8000s	14.0/s	n	Y
4.		Fujifilm X-T4	3690	n	3.0 / 1620	swivel	Y	1/8000s	15.0/s	n	Y
5.		Nikon Z6 II	3690	Y	3.2 / 2100	tilting	Y	1/8000s	14.0/s	n	Y
6.		Panasonic S5	2360	n	3.0 / 1840	swivel	Y	1/8000s	7.0/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 II	optical	Y	3.0 / 921	fixed	n	1/8000s	7.0/s	Y	Y
10.		Pentax K-70	optical	n	3.0 / 921	swivel	n	1/6000s	6.0/s	Y	Y
11.		Pentax KP	optical	n	3.0 / 921	tilting	n	1/6000s	7.0/s	Y	Y
12.		Pentax K-S2	optical	n	3.0 / 921	swivel	n	1/6000s	5.4/s	Y	Y
13.		Sony A7 II	2400	n	3.0 / 1230	tilting	n	1/8000s	5.0/s	n	Y
14.		Sony A77 II	2359	Y	3.0 / 1229	full-flex	n	1/8000s	12.0/s	Y	Y
15.		Sony A99	2359	Y	3.0 / 1229	full-flex	n	1/8000s	6.0/s	n	Y
16.		Sony A6500	2359	n	3.0 / 922	tilting	Y	1/4000s	11.0/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 K-3 III has a touchscreen, while the A77 has a conventional panel. Touch control can be particularly helpful, for example, for setting the focus point.

The Pentax K-3 III 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-3 III writes its imaging data to SDXC cards, while the A77 uses SDXC or Memory Stick PRO Duo cards. The K-3 III features dual card slots, which can be very useful in case a memory card fails. In contrast, the A77 only has one slot. The K-3 III supports UHS-II cards (on its first slot), while the A77 can use UHS-I 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-3 III and Sony Alpha SLT-A77 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-3 III	Y	stereo / mono	Y	Y	micro	3.2	Y	-	Y
2.		Sony A77	Y	stereo / mono	Y	-	mini	2.0	-	-	-
3.		Fujifilm X-H1	Y	stereo / mono	Y	-	micro	3.0	Y	-	-
4.		Fujifilm X-T4	Y	stereo / mono	Y	-	micro	3.1	Y	-	Y
5.		Nikon Z6 II	Y	stereo / mono	Y	Y	micro	3.2	Y	-	Y
6.		Panasonic S5	Y	stereo / mono	Y	Y	micro	3.2	Y	-	Y
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 II	Y	stereo / mono	Y	-	mini	2.0	-	-	-
10.		Pentax K-70	Y	stereo / mono	Y	-	mini	2.0	Y	-	-
11.		Pentax KP	Y	stereo / mono	Y	-	-	2.0	Y	-	-
12.		Pentax K-S2	Y	mono / mono	Y	-	micro	2.0	Y	Y	-
13.		Sony A7 II	Y	stereo / mono	Y	Y	micro	2.0	Y	Y	-
14.		Sony A77 II	Y	stereo / mono	Y	-	mini	2.0	Y	Y	-
15.		Sony A99	Y	stereo / mono	Y	Y	mini	2.0	-	-	-
16.		Sony A6500	Y	stereo / mono	Y	-	micro	2.0	Y	Y	-

It is notable that the K-3 III has a headphone jack, which is not present on the A77 This port makes it possible to attach external headphones and monitor the quality of sound during the recording process.

Both cameras feature a PC Sync terminal to control professional strobe lights, which will be appreciated by studio photographers.

Travel and landscape photographers will find it useful that both cameras feature internal geolocalization sensors and can record GPS coordinates in their EXIF data.

The K-3 III is a recent model that features in the current product line-up of Pentax. In contrast, the A77 has been discontinued (but can be found pre-owned on ebay). As a replacement in the same line of cameras, the A77 was succeeded by the Sony A77 II. Further information on the features and operation of the K-3 III and A77 can be found, respectively, in the Pentax K-3 III Manual (free pdf) or the online Sony A77 Manual.

Review summary

So what is the bottom line? Is the Pentax K-3 III better than the Sony A77 or vice versa? Below is a summary of the relative strengths of each of the two contestants.

Arguments in favor of the Pentax K-3 III:

• Maximized detail: Lacks an anti-alias filter to exploit the sensor's full resolution potential.
• High quality composites: Can combine several shots after pixel-shifting its sensor.
• Better video: Provides higher definition movie capture (4K/30p vs 1080/60p).
• Better sound control: Has a headphone port that enables audio monitoring while recording.
• Brighter framing: Features an optical viewfinder for clear, lag-free composition.
• Larger screen: Has a bigger rear LCD (3.2" vs 3.0") for image review and settings control.
• More detailed LCD: Has a higher resolution rear screen (1620k vs 921k dots).
• Fewer buttons to press: Is equipped with a touch-sensitive rear screen to facilitate handling.
• Easier time-lapse photography: Has an intervalometer built-in for low frequency shooting.
• Longer lasting: Can take more shots (800 versus 470) on a single battery charge.
• Faster data transfer: Supports a more advanced USB protocol (3.2 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.
• Greater peace of mind: Features a second card slot as a backup in case of memory card failure.
• Faster buffer clearing: Supports a more advanced SD data transfer standard (UHS-II vs UHS-I).
• More modern: Reflects 9 years and 7 months of technical progress since the A77 launch.

Advantages of the Sony Alpha SLT-A77:

• Better moiré control: Has an anti-alias filter to avoid artificial patterns to appear in images.
• More framing info: Has an electronic viewfinder that displays shooting data.
• Larger viewfinder image: Features a viewfinder with a higher magnification (0.73x vs 0.70x).
• More flexible LCD: Has a full-flex screen for odd-angle shots in portrait or landscape orientation.
• More selfie-friendly: Has an articulated screen that can be turned to be front-facing.
• Less heavy: Has a lower weight (by 88g or 11 percent) and is thus easier to take along.
• Easier fill-in: Has a small integrated flash to brighten shadows of backlit subjects.
• More affordable: Was introduced into a lower priced category (30 percent cheaper at launch).
• More heavily discounted: Has been around for much longer (launched in August 2011).

If the number of relative strengths (bullet points above) is taken as a guide, the K-3 III is the clear winner of the match-up (16 : 9 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-3 III and the Sony A77 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 incomplete and does no justice, for example, to the way the K-3 III or the A77 perform in practice. 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 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 (USD)	Street Price
1.		Pentax K-3 III	4/5	..	3/5	..	4.5/5	..	Mar 2021	1,999	amazon.com
2.		Sony A77	5/5	91/100	..	81/100	..	5/5	Aug 2011	1,399	ebay.com
3.		Fujifilm X-H1	..	+	5/5	86/100	4.5/5	4.5/5	Feb 2018	1,899	ebay.com
4.		Fujifilm X-T4	5/5	+ +	5/5	88/100	5/5	5/5	Feb 2020	1,699	ebay.com
5.		Nikon Z6 II	4.5/5	..	4/5	89/100	4.5/5	4.5/5	Oct 2020	1,999	amazon.com
6.		Panasonic S5	4.5/5	+ +	4.5/5	88/100	4.5/5	4.5/5	Sep 2020	1,999	amazon.com
7.		Pentax K-3	4/5	..	..	83/100	5/5	5/5	Oct 2013	1,299	ebay.com
8.		Pentax K-3 II	4.5/5	..	..	..	5/5	5/5	Apr 2015	1,099	ebay.com
9.		Pentax K-5 II	5/5	..	..	80/100	5/5	4.5/5	Sep 2012	1,099	ebay.com
10.		Pentax K-70	4.5/5	..	4/5	79/100	4.5/5	4.5/5	Jun 2016	649	ebay.com
11.		Pentax KP	4/5	..	3/5	82/100	5/5	4.5/5	Jan 2017	1,099	ebay.com
12.		Pentax K-S2	4.5/5	..	..	..	5/5	4.5/5	Feb 2015	749	ebay.com
13.		Sony A7 II	5/5	+	4/5	82/100	4.5/5	5/5	Nov 2014	1,999	ebay.com
14.		Sony A77 II	4/5	..	..	80/100	4.5/5	5/5	May 2014	1,199	ebay.com
15.		Sony A99	5/5	..	..	84/100	4.5/5	4.5/5	Sep 2012	2,799	ebay.com
16.		Sony A6500	5/5	+ +	3.5/5	85/100	4.5/5	4.5/5	Oct 2016	1,399	ebay.com
Note: (+ +) highly recommended; (+) recommended; (o) reviewed; (..) not available.

The review scores listed above should be treated 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. 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, please note that some of the review sites have changed their methodology and reporting over time.

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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. As an alternative, you can also directly jump to any one of the listed comparisons that were previously generated by the CAM-parator tool.

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