Olympus E-PM2 vs Sony A77

The Olympus PEN E-PM2 and the Sony Alpha SLT-A77 are two digital cameras that were announced, respectively, in September 2012 and August 2011. The E-PM2 is a mirrorless interchangeable lens camera, while the A77 is a DSLR. The cameras are based on a Four Thirds (E-PM2) and an APS-C (A77) sensor. The Olympus has a resolution of 15.9 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

Olympus E-PM2		Sony A77
Mirrorless system camera		Digital single lens reflex
Micro Four Thirds lenses		Sony A mount lenses
15.9 MP – Four Thirds sensor		24 MP – APS-C sensor
1080/30p Video		1080/60p Video
ISO 100-25,600		ISO 100-16,000 (50 - 25,600)
Viewfinder optional		Electronic viewfinder (2359k dots)
3.0" LCD – 460k dots		3.0" LCD – 921k dots
Fixed touchscreen		Fully flexible screen (no touchscreen)
8 shutter flaps per second		12 shutter flaps per second
In-body stabilization		In-body stabilization
not weather sealed		Weathersealed body
360 shots per battery charge		470 shots per battery charge
110 x 64 x 34 mm, 269 g		143 x 104 x 81 mm, 732 g

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Going beyond this snapshot of core features and characteristics, what are the differences between the Olympus PEN E-PM2 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

The physical size and weight of the Olympus E-PM2 and the Sony A77 are illustrated in the side-by-side display below. 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.

The E-PM2 can be obtained in four different colors (black, silver, red, white), 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 considerably larger (111 percent) than the Olympus E-PM2. Moreover, the A77 is substantially heavier (172 percent) than the E-PM2. It is noteworthy in this context that the A77 is splash and dust-proof, while the E-PM2 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 E-PM2 gets 360 shots out of its Olympus BLS-5 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.		Olympus E-PM2	110 mm	64 mm	34 mm	269 g	360	n	Sep 2012	499	ebay.com
2.		Sony A77	143 mm	104 mm	81 mm	732 g	470	Y	Aug 2011	1,399	ebay.com
3.		Olympus E-M10 II	120 mm	83 mm	47 mm	390 g	320	n	Aug 2015	649	ebay.com
4.		Olympus E-P5	122 mm	69 mm	37 mm	420 g	330	n	May 2013	999	ebay.com
5.		Olympus E-PL3	110 mm	64 mm	37 mm	313 g	300	n	Jun 2011	599	ebay.com
6.		Olympus E-PL5	111 mm	64 mm	38 mm	325 g	360	n	Sep 2012	599	ebay.com
7.		Olympus E-PL6	111 mm	64 mm	38 mm	325 g	360	n	May 2013	599	ebay.com
8.		Olympus E-PL7	115 mm	67 mm	38 mm	357 g	350	n	Aug 2014	599	ebay.com
9.		Olympus E-PL8	115 mm	67 mm	38 mm	357 g	350	n	Sep 2016	549	ebay.com
10.		Olympus E-PL9	117 mm	68 mm	39 mm	380 g	350	n	Feb 2018	599	ebay.com
11.		Olympus E-PM1	110 mm	64 mm	34 mm	265 g	330	n	Jun 2011	499	ebay.com
12.		Panasonic GX850	107 mm	65 mm	33 mm	269 g	210	n	Jan 2017	549	ebay.com
13.		Pentax K-3	131 mm	100 mm	77 mm	800 g	560	Y	Oct 2013	1,299	ebay.com
14.		Sony A7 II	127 mm	96 mm	60 mm	599 g	350	Y	Nov 2014	1,999	ebay.com
15.		Sony A77 II	143 mm	104 mm	81 mm	647 g	480	Y	May 2014	1,199	ebay.com
16.		Sony A99	147 mm	111 mm	78 mm	812 g	500	Y	Sep 2012	2,799	ebay.com
17.		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.
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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 E-PM2 was launched at a markedly lower price (by 64 percent) than the A77, 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 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 are more costly to manufacture and tend to lead to bigger and heavier cameras and lenses.

Of the two cameras under consideration, the Olympus E-PM2 features a Four Thirds sensor and the Sony A77 an APS-C sensor. The sensor area in the A77 is 63 percent bigger. As a result of these sensor size differences, the cameras have a format factor of, respectively, 2.0 and 1.5. The sensor in the E-PM2 has a native 4:3 aspect ratio, while the one in the A77 offers a 3:2 aspect.

With 24MP, the A77 offers a higher resolution than the E-PM2 (15.9MP), but the A77 nevertheless has larger individual pixels (pixel pitch of 3.91μm versus 3.76μm for the E-PM2) due to its larger sensor. However, the E-PM2 is a somewhat more recent model (by 1 year) than the A77, and its sensor might have benefitted from technological advances during this time that enhance the light gathering capacity of its pixel-units.

The resolution advantage of the Sony A77 implies greater flexibility for cropping images or the possibility to print larger pictures. The maximum print size of the A77 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 Olympus E-PM2 are 23 x 17.3 inches or 58.5 x 43.9 cm for good quality, 18.4 x 13.8 inches or 46.8 x 35.1 cm for very good quality, and 15.4 x 11.5 inches or 39 x 29.3 cm for excellent quality prints.

The Olympus PEN E-PM2 has a native sensitivity range from ISO 100 to ISO 25600. 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"). Of the two cameras under consideration, the A77 has a markedly higher DXO score than the E-PM2 (overall score 6 points higher), which will translate into better image quality. The advantage is based on 1.3 bits higher color depth, 1 EV in additional dynamic range, and 0.2 stops of reduced 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.		Olympus E-PM2	Four Thirds	15.9	4608	3456	1080/30p	22.7	12.2	932	72
2.		Sony A77	APS-C	24.0	6000	4000	1080/60p	24.0	13.2	801	78
3.		Olympus E-M10 II	Four Thirds	15.9	4608	3456	1080/60p	23.1	12.5	842	73
4.		Olympus E-P5	Four Thirds	15.9	4608	3456	1080/30p	22.8	12.4	895	72
5.		Olympus E-PL3	Four Thirds	12.2	4032	3024	1080/60i	20.9	10.3	499	52
6.		Olympus E-PL5	Four Thirds	15.9	4608	3456	1080/30p	22.8	12.3	889	72
7.		Olympus E-PL6	Four Thirds	15.9	4608	3456	1080/30p	22.5	12.0	717	68
8.		Olympus E-PL7	Four Thirds	15.9	4608	3456	1080/30p	22.7	12.4	873	72
9.		Olympus E-PL8	Four Thirds	15.9	4608	3456	1080/30p	23.0	12.6	1030	73
10.		Olympus E-PL9	Four Thirds	15.9	4608	3456	4K/30p	23.1	12.8	1162	74
11.		Olympus E-PM1	Four Thirds	12.2	4032	3024	1080/60i	21.0	10.3	499	52
12.		Panasonic GX850	Four Thirds	15.8	4592	3448	4K/30p	23.2	13.3	586	73
13.		Pentax K-3	APS-C	24.1	6016	4000	1080/60i	23.7	13.4	1216	80
14.		Sony A7 II	Full Frame	24.0	6000	4000	1080/60p	24.9	13.6	2449	90
15.		Sony A77 II	APS-C	24.0	6000	4000	1080/60p	24.4	13.4	1013	82
16.		Sony A99	Full Frame	24.0	6000	4000	1080/60p	25.0	14.0	1555	89
17.		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 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 A77 provides a faster frame rate than the E-PM2. It can shoot movie footage at 1080/60p, while the Olympus is limited to 1080/30p.

Feature comparison

Beyond body and sensor, cameras can and do differ across a range of features. For example, the A77 has an electronic viewfinder (2359k dots), which can be very helpful when shooting in bright sunlight. In contrast, the E-PM2 relies on live view and the rear LCD for framing. That said, the E-PM2 can be equipped with an optional viewfinder – the VF-4. The adjacent table lists some of the other core features of the Olympus E-PM2 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.		Olympus E-PM2	optional	n	3.0 / 460	fixed	Y	1/4000s	8.0/s	n	Y
2.		Sony A77	2359	Y	3.0 / 921	full-flex	n	1/8000s	12.0/s	Y	Y
3.		Olympus E-M10 II	2360	n	3.0 / 1040	tilting	Y	1/4000s	8.0/s	Y	Y
4.		Olympus E-P5	optional	n	3.0 / 1037	tilting	Y	1/8000s	9.0/s	Y	Y
5.		Olympus E-PL3	optional	n	3.0 / 460	tilting	n	1/4000s	5.5/s	n	Y
6.		Olympus E-PL5	optional	n	3.0 / 460	tilting	Y	1/4000s	8.0/s	n	Y
7.		Olympus E-PL6	optional	n	3.0 / 460	tilting	Y	1/4000s	8.0/s	n	Y
8.		Olympus E-PL7	optional	n	3.0 / 1037	tilting	Y	1/4000s	8.0/s	n	Y
9.		Olympus E-PL8	optional	n	3.0 / 1037	tilting	Y	1/4000s	8.0/s	n	Y
10.		Olympus E-PL9	none	n	3.0 / 1040	tilting	Y	1/4000s	8.6/s	Y	Y
11.		Olympus E-PM1	optional	n	3.0 / 460	fixed	n	1/4000s	5.5/s	n	Y
12.		Panasonic GX850	none	n	3.0 / 1040	tilting	Y	1/500s	10.0/s	Y	n
13.		Pentax K-3	optical	Y	3.2 / 1037	fixed	n	1/8000s	8.3/s	Y	Y
14.		Sony A7 II	2400	n	3.0 / 1230	tilting	n	1/8000s	5.0/s	n	Y
15.		Sony A77 II	2359	Y	3.0 / 1229	full-flex	n	1/8000s	12.0/s	Y	Y
16.		Sony A99	2359	Y	3.0 / 1229	full-flex	n	1/8000s	6.0/s	n	Y
17.		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 E-PM2 has a touchscreen, while the A77 has a conventional panel. Touch control can be particularly helpful, for example, for setting the focus point.

The E-PM2 writes its imaging data to SDXC cards, while the A77 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 Olympus PEN E-PM2 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.		Olympus E-PM2	Y	stereo / mono	-	-	mini	2.0	-	-	-
2.		Sony A77	Y	stereo / mono	Y	-	mini	2.0	-	-	-
3.		Olympus E-M10 II	Y	stereo / mono	-	-	micro	2.0	Y	-	-
4.		Olympus E-P5	Y	stereo / mono	-	-	micro	2.0	Y	-	-
5.		Olympus E-PL3	Y	stereo / -	-	-	mini	2.0	-	-	-
6.		Olympus E-PL5	Y	stereo / mono	-	-	mini	2.0	-	-	-
7.		Olympus E-PL6	Y	stereo / mono	-	-	mini	2.0	-	-	-
8.		Olympus E-PL7	Y	stereo / mono	-	-	micro	2.0	Y	-	-
9.		Olympus E-PL8	Y	stereo / mono	-	-	micro	2.0	Y	-	-
10.		Olympus E-PL9	Y	stereo / mono	-	-	micro	2.0	Y	-	Y
11.		Olympus E-PM1	Y	stereo / mono	-	-	mini	2.0	-	-	-
12.		Panasonic GX850	-	stereo / mono	-	-	micro	2.0	Y	-	-
13.		Pentax K-3	Y	mono / mono	Y	Y	mini	3.0	-	-	-
14.		Sony A7 II	Y	stereo / mono	Y	Y	micro	2.0	Y	Y	-
15.		Sony A77 II	Y	stereo / mono	Y	-	mini	2.0	Y	Y	-
16.		Sony A99	Y	stereo / mono	Y	Y	mini	2.0	-	-	-
17.		Sony A6500	Y	stereo / mono	Y	-	micro	2.0	Y	Y	-

It is notable that the A77 has a microphone port, which can help to improve the quality of audio recordings by attaching an external microphone. The E-PM2 does not feature such a mic input.

Studio photographers will appreciate that the Sony A77 (unlike the E-PM2) features a PC Sync socket, so that professional strobe lights can be controlled by the camera.

Travel and landscape photographers will find it useful that the A77 has an internal geolocalization sensor and can record GPS coordinates in its EXIF data.

Both the E-PM2 and the A77 have been discontinued, but can regularly be found used on ebay. The A77 was replaced by the Sony A77 II, while the E-PM2 does not have a direct successor. Further information on the features and operation of the E-PM2 and A77 can be found, respectively, in the Olympus E-PM2 Manual (free pdf) or the online Sony A77 Manual.

Review summary

So what is the bottom line? Which of the two cameras – the Olympus E-PM2 or the Sony A77 – has the upper hand? Is one clearly better than the other? The listing below highlights the relative strengths of the two models.

Arguments in favor of the Olympus PEN E-PM2:

• Fewer buttons to press: Is equipped with a touch-sensitive rear screen to facilitate handling.
• More compact: Is smaller (110x64mm vs 143x104mm) and thus needs less room in the bag.
• Less heavy: Is lighter (by 463g or 63 percent) and hence easier to carry around.
• More legacy lens friendly: Can take a broad range of non-native lenses via adapters.
• More affordable: Was introduced into a lower priced category (64 percent cheaper at launch).
• More modern: Is somewhat more recent (announced 1 year after the A77).

Advantages of the Sony Alpha SLT-A77:

• More detail: Has more megapixels (24 vs 15.9MP), which boosts linear resolution by 25%.
• Better image quality: Scores markedly higher (6 points) in the DXO overall evaluation.
• Richer colors: Generates noticeably more natural colors (1.3 bits more color depth).
• More dynamic range: Captures a broader range of light and dark details (1 EV of extra DR).
• Better video: Provides higher movie framerates (1080/60p versus 1080/30p).
• Better sound: Can connect to an external microphone for higher quality sound recording.
• Easier framing: Has an electronic viewfinder for image composition and settings control.
• Easier setting verification: Features a control panel on top to check shooting parameters.
• More detailed LCD: Has a higher resolution rear screen (921k vs 460k 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.
• Faster shutter: Has higher mechanical shutter speed (1/8000s vs 1/4000s) to freeze action.
• Faster burst: Shoots at higher frequency (12 vs 8 flaps/sec) to capture the decisive moment.
• Longer lasting: Gets more shots (470 versus 360) out of a single battery charge.
• Better sealing: Is splash and dust sealed for shooting in inclement weather conditions.
• Easier fill-in: Has a small integrated flash to brighten shadows of backlit subjects.
• Easier geotagging: Features an internal GPS sensor to log localization data.
• 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 August 2011).

If the number of relative strengths (bullet points above) is taken as a guide, the A77 is the clear winner of the contest (19 : 6 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 Olympus E-PM2 and the Sony A77 place the cameras among the top in their class? Find out in the latest Best Mirrorless Interchangeable Lens Camera and Best DSLR 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 incomplete and does no justice, for example, to the way the E-PM2 or the A77 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 where reviews by experts come in. The following table reports the overall ratings of the cameras as published by some of the major 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.		Olympus E-PM2	3/5	..	..	77/100	5/5	4.5/5	Sep 2012	499	ebay.com
2.		Sony A77	5/5	91/100	..	81/100	..	5/5	Aug 2011	1,399	ebay.com
3.		Olympus E-M10 II	4.5/5	+ +	..	80/100	5/5	5/5	Aug 2015	649	ebay.com
4.		Olympus E-P5	5/5	+ +	..	78/100	4.5/5	5/5	May 2013	999	ebay.com
5.		Olympus E-PL3	3/5	+ +	..	72/100	4.5/5	4/5	Jun 2011	599	ebay.com
6.		Olympus E-PL5	3/5	+ +	..	..	4.5/5	4.5/5	Sep 2012	599	ebay.com
7.		Olympus E-PL6	..	..	..	..	..	..	May 2013	599	ebay.com
8.		Olympus E-PL7	4/5	+	..	..	5/5	4/5	Aug 2014	599	ebay.com
9.		Olympus E-PL8	..	..	..	..	4.5/5	4/5	Sep 2016	549	ebay.com
10.		Olympus E-PL9	..	+	..	..	4.5/5	4/5	Feb 2018	599	ebay.com
11.		Olympus E-PM1	..	86/100	..	71/100	4.5/5	4.5/5	Jun 2011	499	ebay.com
12.		Panasonic GX850	..	+	..	76/100	4.5/5	4.5/5	Jan 2017	549	ebay.com
13.		Pentax K-3	4/5	..	..	83/100	5/5	5/5	Oct 2013	1,299	ebay.com
14.		Sony A7 II	5/5	+	4/5	82/100	4.5/5	5/5	Nov 2014	1,999	ebay.com
15.		Sony A77 II	4/5	..	..	80/100	4.5/5	5/5	May 2014	1,199	ebay.com
16.		Sony A99	5/5	..	..	84/100	4.5/5	4.5/5	Sep 2012	2,799	ebay.com
17.		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.

Care should be taken when interpreting the review scores above, though. The ratings are only valid when referring to cameras in the same category and of the same age. Hence, a score should always be seen in the context of the camera's market launch date and its price, and comparisons of ratings among very different cameras or across long time periods have little meaning. Also, kindly note that some of the listed sites have over time developped their review approaches and their reporting style.

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Other camera comparisons

Did this review help to inform your camera decision process? In case you would like to check on the differences and similarities of other camera models, just make your choice using the following search menu. There is also a set of direct links to comparison reviews that other users of the CAM-parator app explored.

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