Sony A99 vs Pentax K-3

The Sony Alpha SLT-A99 and the Pentax K-3 are two digital cameras that were officially introduced, respectively, in September 2012 and October 2013. Both are DSLR (Digital Single Lens Reflex) cameras that are based on a full frame (A99) and an APS-C (K-3) sensor. The Sony has a resolution of 24 megapixels, whereas the Pentax provides 24.1 MP.

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

Headline Specifications

Sony A99		Pentax K-3
Digital single lens reflex		Digital single lens reflex
Sony A mount lenses		Pentax K mount lenses
24 MP – Full Frame sensor		24.1 MP – APS-C sensor
1080/60p Video		1080/60i Video
ISO 100-25,600		ISO 100-51,200
Electronic viewfinder (2359k dots)		Optical viewfinder
3.0" LCD – 1229k dots		3.2" LCD – 1037k dots
Fully flexible screen (no touchscreen)		Fixed screen (not touch-sensitive)
6 shutter flaps per second		8.3 shutter flaps per second
In-body stabilization		In-body stabilization
Weathersealed body		Weathersealed body
500 shots per battery charge		560 shots per battery charge
147 x 111 x 78 mm, 812 g		131 x 100 x 77 mm, 800 g

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Going beyond this snapshot of core features and characteristics, what are the differences between the Sony Alpha SLT-A99 and the Pentax K-3? 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 Sony A99 and the Pentax K-3 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 can be obtained in two different colors (black, silver), while the A99 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-3 is notably smaller (20 percent) than the Sony A99. Moreover, the K-3 is slightly lighter (1 percent) than the A99. 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 A99 gets 500 shots out of its Sony NP-FM500H battery, while the K-3 can take 560 images on a single charge of its Pentax D-LI90 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.		Sony A99	147 mm	111 mm	78 mm	812 g	500	Y	Sep 2012	2,799	ebay.com
2.		Pentax K-3	131 mm	100 mm	77 mm	800 g	560	Y	Oct 2013	1,299	ebay.com
3.		Canon R6	138 mm	98 mm	88 mm	680 g	360	Y	Jul 2020	2,499	amazon.com
4.		Nikon D7100	136 mm	107 mm	76 mm	765 g	950	Y	Feb 2013	1,199	ebay.com
5.		Pentax K-3 II	131 mm	100 mm	77 mm	800 g	720	Y	Apr 2015	1,099	ebay.com
6.		Pentax K-5 II	131 mm	97 mm	73 mm	760 g	740	Y	Sep 2012	1,099	ebay.com
7.		Pentax KP	132 mm	101 mm	76 mm	703 g	390	Y	Jan 2017	1,099	ebay.com
8.		Sony A7R II	127 mm	96 mm	60 mm	625 g	290	Y	Jun 2015	3,199	ebay.com
9.		Sony A7R III	127 mm	96 mm	74 mm	650 g	650	Y	Oct 2017	3,199	ebay.com
10.		Sony A7S II	127 mm	96 mm	60 mm	627 g	370	Y	Sep 2015	2,999	ebay.com
11.		Sony A9	127 mm	96 mm	63 mm	673 g	650	Y	Apr 2017	4,499	ebay.com
12.		Sony A9 II	129 mm	96 mm	76 mm	678 g	690	Y	Oct 2019	4,499	amazon.com
13.		Sony A77	143 mm	104 mm	81 mm	732 g	470	Y	Aug 2011	1,399	ebay.com
14.		Sony A99 II	143 mm	104 mm	76 mm	849 g	490	Y	Sep 2016	3,199	ebay.com
15.		Sony A850	156 mm	117 mm	82 mm	895 g	880	Y	Aug 2009	1,999	ebay.com
16.		Sony A900	156 mm	117 mm	82 mm	895 g	880	Y	Sep 2008	2,999	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 K-3 was launched at a markedly lower price (by 54 percent) than the A99, 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. 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 tend to be associated with larger, more expensive camera bodies and lenses.

Of the two cameras under consideration, the Sony A99 features a full frame sensor and the Pentax K-3 an APS-C sensor. The sensor area in the K-3 is 57 percent smaller. As a result of these sensor size differences, the cameras have a format factor of, respectively, 1.0 and 1.5. Both cameras have a native aspect ratio (sensor width to sensor height) of 3:2.

Despite having a smaller sensor, the K-3 offers a slightly higher resolution of 24.1 megapixels, compared with 24 MP of the A99. 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 3.90μm versus 5.96μm for the A99). However, it should be noted that the K-3 is a somewhat more recent model (by 1 year) than the A99, 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-3 has no anti-alias filter installed, so that it can capture all the detail its sensor resolves.

The Sony Alpha SLT-A99 has a native sensitivity range from ISO 100 to ISO 25600, which can be extended to ISO 50-25600. The corresponding ISO settings for the Pentax K-3 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 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 A99 has a notably higher overall DXO score than the K-3 (overall score 9 points higher), which gives it an advantage in terms of imaging quality. This advantage is based on 1.3 bits higher color depth, 0.6 EV in additional dynamic range, and 0.4 stops in additional low light sensitivity. 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.		Sony A99	Full Frame	24.0	6000	4000	1080/60p	25.0	14.0	1555	89
2.		Pentax K-3	APS-C	24.1	6016	4000	1080/60i	23.7	13.4	1216	80
3.		Canon R6	Full Frame	20.0	5472	3648	4k/60p	24.2	14.3	3394	90
4.		Nikon D7100	APS-C	24.0	6000	4000	1080/60p	24.2	13.7	1256	83
5.		Pentax K-3 II	APS-C	24.1	6016	4000	1080/60i	23.6	13.6	1106	80
6.		Pentax K-5 II	APS-C	16.1	4928	3264	1080/25p	23.8	14.1	1235	82
7.		Pentax KP	APS-C	24.1	6016	4000	1080/60i	23.9	13.2	1699	81
8.		Sony A7R II	Full Frame	42.2	7952	5304	4K/30p	26.0	13.9	3434	98
9.		Sony A7R III	Full Frame	42.2	7952	5304	4K/30p	26.0	14.7	3523	100
10.		Sony A7S II	Full Frame	12.0	4240	2832	4K/30p	23.6	13.3	2993	85
11.		Sony A9	Full Frame	24.0	6000	4000	4K/30p	24.9	13.3	3517	92
12.		Sony A9 II	Full Frame	24.0	6000	4000	4K/30p	25.0	14.0	3434	93
13.		Sony A77	APS-C	24.0	6000	4000	1080/60p	24.0	13.2	801	78
14.		Sony A99 II	Full Frame	42.2	7952	5304	4K/30p	25.4	13.4	2317	92
15.		Sony A850	Full Frame	24.4	6048	4032	none	23.8	12.2	1415	79
16.		Sony A900	Full Frame	24.4	6048	4032	none	23.7	12.3	1431	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. Both cameras under consideration are equipped with sensors that have a sufficiently high read-out speed for moving images, but the A99 provides a higher frame rate than the K-3. It can shoot video footage at 1080/60p, while the Pentax is limited to 1080/60i.

Feature comparison

Apart from body and sensor, cameras can and do differ across a range of features. For example, the A99 has an electronic viewfinder (2359k dots), while the K-3 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 A99 has a higher magnification than the one of the K-3 (0.71x 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 Sony A99 and Pentax K-3 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.		Sony A99	2359	Y	3.0 / 1229	full-flex	n	1/8000s	6.0/s	n	Y
2.		Pentax K-3	optical	Y	3.2 / 1037	fixed	n	1/8000s	8.3/s	Y	Y
3.		Canon R6	3690	n	3.0 / 1620	swivel	Y	1/8000s	12.0/s	n	Y
4.		Nikon D7100	optical	Y	3.2 / 1229	fixed	n	1/8000s	6.0/s	Y	n
5.		Pentax K-3 II	optical	Y	3.2 / 1037	fixed	n	1/8000s	8.3/s	n	Y
6.		Pentax K-5 II	optical	Y	3.0 / 921	fixed	n	1/8000s	7.0/s	Y	Y
7.		Pentax KP	optical	n	3.0 / 921	tilting	n	1/6000s	7.0/s	Y	Y
8.		Sony A7R II	2400	n	3.0 / 1229	tilting	n	1/8000s	5.0/s	n	Y
9.		Sony A7R III	3686	n	3.0 / 1440	tilting	Y	1/8000s	10.0/s	n	Y
10.		Sony A7S II	2400	n	3.0 / 1229	tilting	n	1/8000s	5.0/s	n	Y
11.		Sony A9	3686	n	3.0 / 1440	tilting	Y	1/8000s	20.0/s	n	Y
12.		Sony A9 II	3686	n	3.0 / 1440	tilting	Y	1/8000s	20.0/s	n	Y
13.		Sony A77	2359	Y	3.0 / 921	full-flex	n	1/8000s	12.0/s	Y	Y
14.		Sony A99 II	2400	Y	3.0 / 1229	full-flex	n	1/8000s	12.0/s	n	Y
15.		Sony A850	optical	Y	3.0 / 922	fixed	n	1/8000s	3.0/s	n	Y
16.		Sony A900	optical	Y	3.0 / 922	fixed	n	1/8000s	5.0/s	n	Y
Note: *) Information refers to the mechanical shutter, unless the camera only has an electronic one.

One difference between the cameras concerns the presence of an on-board flash. The K-3 has one, while the A99 does not. While the built-in flash of the K-3 is not very powerful, it can at times be useful as a fill-in light.

The Pentax K-3 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 A99 writes its imaging data to SDXC or Memory Stick PRO Duo cards, while the K-3 uses SDXC cards. Both cameras feature dual card slots, which can be very useful in case a memory card fails. 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 Sony Alpha SLT-A99 and Pentax K-3 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.		Sony A99	Y	stereo / mono	Y	Y	mini	2.0	-	-	-
2.		Pentax K-3	Y	mono / mono	Y	Y	mini	3.0	-	-	-
3.		Canon R6	Y	mono / mono	Y	Y	micro	3.2	Y	-	Y
4.		Nikon D7100	Y	stereo / mono	Y	Y	mini	2.0	-	-	-
5.		Pentax K-3 II	Y	mono / mono	Y	Y	mini	3.0	-	-	-
6.		Pentax K-5 II	Y	stereo / mono	Y	-	mini	2.0	-	-	-
7.		Pentax KP	Y	stereo / mono	Y	-	-	2.0	Y	-	-
8.		Sony A7R II	Y	stereo / mono	Y	Y	micro	2.0	Y	Y	-
9.		Sony A7R III	Y	stereo / mono	Y	Y	micro	3.1	Y	Y	Y
10.		Sony A7S II	Y	stereo / mono	Y	Y	micro	2.0	Y	Y	-
11.		Sony A9	Y	stereo / mono	Y	Y	micro	2.0	Y	Y	Y
12.		Sony A9 II	Y	stereo / mono	Y	Y	micro	3.1	Y	Y	Y
13.		Sony A77	Y	stereo / mono	Y	-	mini	2.0	-	-	-
14.		Sony A99 II	Y	stereo / mono	Y	Y	micro	2.0	Y	Y	Y
15.		Sony A850	Y	- / -	-	-	mini	2.0	-	-	-
16.		Sony A900	Y	- / -	-	-	mini	2.0	-	-	-

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 the A99 has an internal geolocalization sensor and can record GPS coordinates in its EXIF data.

Both the A99 and the K-3 have been discontinued, but can regularly be found used on ebay. The A99 was replaced by the Sony A99, while the K-3 was followed by the Pentax K-3 II. Further information on the features and operation of the A99 and K-3 can be found, respectively, in the Sony A99 Manual (free pdf) or the online Pentax K-3 Manual.

Review summary

So what is the bottom line? Is the Sony A99 better than the Pentax K-3 or vice versa? Below is a summary of the relative strengths of each of the two contestants.

Arguments in favor of the Sony Alpha SLT-A99:

• Better moiré control: Has an anti-alias filter to avoid artificial patterns to appear in images.
• Better image quality: Scores markedly higher (9 points) in the DXO overall assessment.
• Richer colors: Generates images with noticeably better colors (1.3 bits more color depth).
• More dynamic range: Captures a larger spectrum of light and dark details (0.6 EV of extra DR).
• Better low-light sensitivity: Requires less light for good images (0.4 stops ISO advantage).
• Better video: Provides higher movie framerates (1080/60p versus 1080/60i).
• More framing info: Has an electronic viewfinder that displays shooting data.
• Larger viewfinder image: Features a viewfinder with a higher magnification (0.71x vs 0.63x).
• More detailed LCD: Has a higher resolution rear screen (1229k vs 1037k dots).
• 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.
• Easier geotagging: Features an internal GPS sensor to log localization data.
• More heavily discounted: Has been on the market for longer (launched in September 2012).

Advantages of the Pentax K-3:

• 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.
• Larger screen: Has a bigger rear LCD (3.2" vs 3.0") for image review and settings control.
• Faster burst: Shoots at higher frequency (8.3 vs 6 flaps/sec) to capture the decisive moment.
• Easier time-lapse photography: Has an intervalometer built-in for low frequency shooting.
• More compact: Is smaller (131x100mm vs 147x111mm) and will fit more readily into a bag.
• Longer lasting: Gets more shots (560 versus 500) out of a single battery charge.
• Easier fill-in: Has a small integrated flash to brighten shadows of backlit subjects.
• Faster data transfer: Supports a more advanced USB protocol (3.0 vs 2.0).
• More affordable: Was introduced into a lower priced category (54 percent cheaper at launch).
• More modern: Was introduced somewhat (1 year) more recently.

If the number of relative strengths (bullet points above) is taken as a guide, the A99 emerges as the winner of the contest (13 : 11 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 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 Sony A99 and the Pentax K-3 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 A99 or the K-3 perform in practice. User reviews, such as those found at amazon, can sometimes inform about these issues, but such feedback is often incomplete, inconsistent, and biased.

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.		Sony A99	5/5	..	..	84/100	4.5/5	4.5/5	Sep 2012	2,799	ebay.com
2.		Pentax K-3	4/5	..	..	83/100	5/5	5/5	Oct 2013	1,299	ebay.com
3.		Canon R6	5/5	+ +	4/5	90/100	4.5/5	5/5	Jul 2020	2,499	amazon.com
4.		Nikon D7100	5/5	+ +	..	85/100	4.5/5	4.5/5	Feb 2013	1,199	ebay.com
5.		Pentax K-3 II	4.5/5	..	..	..	5/5	5/5	Apr 2015	1,099	ebay.com
6.		Pentax K-5 II	5/5	..	..	80/100	5/5	4.5/5	Sep 2012	1,099	ebay.com
7.		Pentax KP	4/5	..	3/5	82/100	5/5	4.5/5	Jan 2017	1,099	ebay.com
8.		Sony A7R II	5/5	+ +	5/5	90/100	5/5	5/5	Jun 2015	3,199	ebay.com
9.		Sony A7R III	..	+ +	4/5	90/100	4.5/5	5/5	Oct 2017	3,199	ebay.com
10.		Sony A7S II	5/5	+	..	..	4.5/5	5/5	Sep 2015	2,999	ebay.com
11.		Sony A9	5/5	+ +	4.8/5	89/100	5/5	5/5	Apr 2017	4,499	ebay.com
12.		Sony A9 II	..	..	5/5	90/100	5/5	5/5	Oct 2019	4,499	amazon.com
13.		Sony A77	5/5	91/100	..	81/100	..	5/5	Aug 2011	1,399	ebay.com
14.		Sony A99 II	..	..	4.5/5	85/100	4.5/5	4.5/5	Sep 2016	3,199	ebay.com
15.		Sony A850	3/5	..	..	75/100	..	4.5/5	Aug 2009	1,999	ebay.com
16.		Sony A900	..	+ +	..	+ +	4.5/5	5/5	Sep 2008	2,999	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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