Olympus E-PM2 vs Pentax 645D

The Olympus PEN E-PM2 and the Pentax 645D are two digital cameras that were officially introduced, respectively, in September 2012 and March 2010. The E-PM2 is a mirrorless interchangeable lens camera, while the 645D is a DSLR. The cameras are based on a Four Thirds (E-PM2) and a medium format (645D) sensor. The Olympus has a resolution of 15.9 megapixels, whereas the Pentax provides 39.5 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		Pentax 645D
Mirrorless system camera		Digital single lens reflex
Micro Four Thirds lenses		Pentax 645 mount lenses
15.9 MP – Four Thirds sensor		39.5 MP – Medium Format sensor
1080/30p Video		no Video
ISO 100-25,600		ISO 100-1,600
Viewfinder optional		Optical viewfinder
3.0" LCD – 460k dots		3.0" LCD – 921k dots
Fixed touchscreen		Fixed screen (not touch-sensitive)
8 shutter flaps per second		1.1 shutter flaps per second
In-body stabilization		Lens stabilization only
not weather sealed		Weathersealed body
360 shots per battery charge		800 shots per battery charge
110 x 64 x 34 mm, 269 g		156 x 117 x 119 mm, 1480 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 Pentax 645D? 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 Pentax 645D are illustrated in the side-by-side display below. The two cameras are presented according to their relative size. Three consecutive views from the front, the top, and the rear side are shown. All width, height and depth measures are rounded to the nearest millimeter.

The E-PM2 can be obtained in four different colors (black, silver, red, white), while the 645D 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 645D is considerably larger (159 percent) than the Olympus E-PM2. Moreover, the 645D is substantially heavier (450 percent) than the E-PM2. It is noteworthy in this context that the 645D 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 645D can take 800 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 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 (USD)	Street Price
1.		Olympus E-PM2	110 mm	64 mm	34 mm	269 g	360	n	Sep 2012	499	ebay.com
2.		Pentax 645D	156 mm	117 mm	119 mm	1480 g	800	Y	Mar 2010	9,995	ebay.com
3.		Canon 1D X	158 mm	168 mm	83 mm	1551 g	1120	Y	Oct 2011	6,799	ebay.com
4.		Canon 1D Mark IV	156 mm	157 mm	80 mm	1230 g	1500	Y	Oct 2009	4,999	ebay.com
5.		Leica S Typ 006	160 mm	120 mm	80 mm	1260 g	..	Y	Sep 2012	21,950	ebay.com
6.		Nikon D3S	160 mm	157 mm	88 mm	1240 g	4200	Y	Oct 2009	5,199	ebay.com
7.		Olympus E-M10 II	120 mm	83 mm	47 mm	390 g	320	n	Aug 2015	649	ebay.com
8.		Olympus E-M10	119 mm	82 mm	46 mm	396 g	320	n	Jan 2014	699	ebay.com
9.		Olympus E-PL7	115 mm	67 mm	38 mm	357 g	350	n	Aug 2014	599	ebay.com
10.		Olympus E-M1	130 mm	94 mm	63 mm	497 g	350	Y	Sep 2013	1,399	ebay.com
11.		Olympus E-P5	122 mm	69 mm	37 mm	420 g	330	n	May 2013	999	ebay.com
12.		Olympus E-PL6	111 mm	64 mm	38 mm	325 g	360	n	May 2013	599	ebay.com
13.		Olympus E-PL5	111 mm	64 mm	38 mm	325 g	360	n	Sep 2012	599	ebay.com
14.		Olympus E-PL3	110 mm	64 mm	37 mm	313 g	300	n	Jun 2011	599	ebay.com
15.		Olympus E-PM1	110 mm	64 mm	34 mm	265 g	330	n	Jun 2011	499	ebay.com
16.		Panasonic G6	122 mm	85 mm	71 mm	390 g	340	n	Apr 2013	599	ebay.com
17.		Pentax 645Z	156 mm	117 mm	123 mm	1550 g	650	Y	Apr 2014	8,499	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 obviously take relative prices into account. The retail prices at the time of the camera’s release place the model in the market relative to other models in the producer’s line-up and the competition. The E-PM2 was launched at a markedly lower price (by 95 percent) than the 645D, 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 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. 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 Pentax 645D a medium format sensor. The sensor area in the 645D is 545 percent bigger. As a result of these sensor size differences, the cameras have a format factor of, respectively, 2.0 and 0.79. Both cameras feature a native aspect ratio (sensor width to sensor height) of 4:3.

With 39.5MP, the 645D offers a higher resolution than the E-PM2 (15.9MP), but the 645D nevertheless has larger individual pixels (pixel pitch of 6.06μm versus 3.76μm for the E-PM2) due to its larger sensor. However, the E-PM2 is a much more recent model (by 2 years and 6 months) than the 645D, and its sensor will have benefitted from technological advances during this time that enhance the light gathering capacity of its pixel-units. Coming back to sensor resolution, it should be mentioned that the 645D has no anti-alias filter installed, so that it can capture all the detail its sensor resolves.

The resolution advantage of the Pentax 645D implies greater flexibility for cropping images or the possibility to print larger pictures. The maximum print size of the 645D for good quality output (200 dots per inch) amounts to 36.3 x 27.2 inches or 92.3 x 69.1 cm, for very good quality (250 dpi) 29.1 x 21.8 inches or 73.8 x 55.3 cm, and for excellent quality (300 dpi) 24.2 x 18.1 inches or 61.5 x 46.1 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 Pentax 645D are ISO 100 to ISO 1600 (no boost).

In terms of underlying technology, the E-PM2 is build around a CMOS sensor, while the 645D uses a CCD imager. Both cameras use a Bayer filter for capturing RGB colors on a square grid of photosensors. This arrangement is found in most digital cameras.

Since 2007, DXO Mark has published sensor performance measurements that have been derived using a consistent methodology. 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 645D has a markedly higher DXO score than the E-PM2 (overall score 10 points higher), which will translate into better image quality. The advantage is based on 1.9 bits higher color depth, 0.4 EV in additional dynamic range, and 0.4 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.		Olympus E-PM2	Four Thirds	15.9	4608	3456	1080/30p	22.7	12.2	932	72
2.		Pentax 645D	Medium Format	39.5	7264	5440	none	24.6	12.6	1262	82
3.		Canon 1D X	Full Frame	17.9	5184	3456	1080/30p	23.8	11.8	2786	82
4.		Canon 1D Mark IV	APS-H	16.0	4896	3264	1080/30p	22.8	12.0	1320	74
5.		Leica S Typ 006	Medium Format	37.5	7500	5000	none	23.9	12.2	824	76
6.		Nikon D3S	Full Frame	12.1	4256	2832	720/24p	23.5	12.0	3253	82
7.		Olympus E-M10 II	Four Thirds	15.9	4608	3456	1080/60p	23.1	12.5	842	73
8.		Olympus E-M10	Four Thirds	15.9	4608	3456	1080/30p	22.8	12.3	884	72
9.		Olympus E-PL7	Four Thirds	15.9	4608	3456	1080/30p	22.7	12.4	873	72
10.		Olympus E-M1	Four Thirds	15.9	4608	3456	1080/30p	23.0	12.7	757	73
11.		Olympus E-P5	Four Thirds	15.9	4608	3456	1080/30p	22.8	12.4	895	72
12.		Olympus E-PL6	Four Thirds	15.9	4608	3456	1080/30p	22.5	12.0	717	68
13.		Olympus E-PL5	Four Thirds	15.9	4608	3456	1080/30p	22.8	12.3	889	72
14.		Olympus E-PL3	Four Thirds	12.2	4032	3024	1080/60i	20.9	10.3	499	52
15.		Olympus E-PM1	Four Thirds	12.2	4032	3024	1080/60i	21.0	10.3	499	52
16.		Panasonic G6	Four Thirds	15.9	4608	3456	1080/60p	21.3	11.5	639	61
17.		Pentax 645Z	Medium Format	51.1	8256	6192	1080/60i	26.0	14.7	4505	101
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 E-PM2 indeed provides movie recording capabilities, while the 645D does not. The highest resolution format that the E-PM2 can use is 1080/30p.

Feature comparison

Apart from body and sensor, cameras can and do differ across a variety of features. For example, the 645D has an optical viewfinder, which can be very useful 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 table below summarizes some of the other core capabilities of the Olympus E-PM2 and Pentax 645D 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.		Olympus E-PM2	optional	n	3.0 / 460	fixed	Y	1/4000s	8.0/s	n	Y
2.		Pentax 645D	optical	Y	3.0 / 921	fixed	n	1/4000s	1.1/s	n	n
3.		Canon 1D X	optical	Y	3.2 / 1040	fixed	n	1/8000s	14.0/s	n	n
4.		Canon 1D Mark IV	optical	Y	3.0 / 920	fixed	n	1/8000s	10.0/s	n	n
5.		Leica S Typ 006	optical	Y	3.0 / 922	fixed	n	1/4000s	1.5/s	n	n
6.		Nikon D3S	optical	Y	3.0 / 921	fixed	n	1/8000s	11.0/s	n	n
7.		Olympus E-M10 II	2360	n	3.0 / 1040	tilting	Y	1/4000s	8.0/s	Y	Y
8.		Olympus E-M10	1440	n	3.0 / 1037	tilting	Y	1/4000s	8.0/s	Y	Y
9.		Olympus E-PL7	optional	n	3.0 / 1037	tilting	Y	1/4000s	8.0/s	n	Y
10.		Olympus E-M1	2360	n	3.0 / 1037	tilting	Y	1/8000s	10.0/s	n	Y
11.		Olympus E-P5	optional	n	3.0 / 1037	tilting	Y	1/8000s	9.0/s	Y	Y
12.		Olympus E-PL6	optional	n	3.0 / 460	tilting	Y	1/4000s	8.0/s	n	Y
13.		Olympus E-PL5	optional	n	3.0 / 460	tilting	Y	1/4000s	8.0/s	n	Y
14.		Olympus E-PL3	optional	n	3.0 / 460	tilting	n	1/4000s	5.5/s	n	Y
15.		Olympus E-PM1	optional	n	3.0 / 460	fixed	n	1/4000s	5.5/s	n	Y
16.		Panasonic G6	1440	n	3.0 / 1036	swivel	Y	1/4000s	7.0/s	Y	n
17.		Pentax 645Z	optical	Y	3.2 / 1037	tilting	n	1/4000s	3.0/s	n	n
Note: *) Information refers to the mechanical shutter, unless the camera only has an electronic one.

One feature that differentiates the E-PM2 and the 645D is in-body image stabilization (IBIS). The E-PM2 reduces the risk of handshake-induced blur with all attached lenses, while the 645D offers no blur reduction with lenses that themselves do not provide optical image stabilization.

The Pentax 645D 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 E-PM2 and the 645D write their files to SDXC cards. The 645D features dual card slots, which can be very useful in case a memory card fails. In contrast, the E-PM2 only has one slot. The E-PM2 supports UHS-I cards (Ultra High Speed data transfer of up to 104 MB/s), while the 645D 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 Olympus PEN E-PM2 and Pentax 645D 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.		Pentax 645D	Y	stereo / -	-	-	-	2.0	-	-	-
3.		Canon 1D X	Y	mono / -	Y	-	mini	2.0	-	-	-
4.		Canon 1D Mark IV	Y	stereo / -	Y	-	mini	2.0	-	-	-
5.		Leica S Typ 006	Y	- / -	-	-	mini	2.0	-	-	-
6.		Nikon D3S	Y	stereo / -	-	-	mini	2.0	-	-	-
7.		Olympus E-M10 II	Y	stereo / mono	-	-	micro	2.0	Y	-	-
8.		Olympus E-M10	Y	stereo / mono	-	-	micro	2.0	Y	-	-
9.		Olympus E-PL7	Y	stereo / mono	-	-	micro	2.0	Y	-	-
10.		Olympus E-M1	Y	stereo / mono	Y	-	micro	2.0	Y	-	-
11.		Olympus E-P5	Y	stereo / mono	-	-	micro	2.0	Y	-	-
12.		Olympus E-PL6	Y	stereo / mono	-	-	mini	2.0	-	-	-
13.		Olympus E-PL5	Y	stereo / mono	-	-	mini	2.0	-	-	-
14.		Olympus E-PL3	Y	stereo / -	-	-	mini	2.0	-	-	-
15.		Olympus E-PM1	Y	stereo / mono	-	-	mini	2.0	-	-	-
16.		Panasonic G6	Y	stereo / mono	Y	-	mini	2.0	Y	Y	-
17.		Pentax 645Z	Y	stereo / mono	Y	-	mini	3.0	-	-	-

Studio photographers will appreciate that the Pentax 645D (unlike the E-PM2) features a PC Sync socket, so that professional strobe lights can be controlled by the camera.

Both the E-PM2 and the 645D have been discontinued, but can regularly be found used on ebay. The 645D was replaced by the Pentax 645Z, while the E-PM2 does not have a direct successor. Further information on the features and operation of the E-PM2 and 645D can be found, respectively, in the Olympus E-PM2 Manual (free pdf) or the online Pentax 645D Manual.

Review summary

So how do things add up? Is there a clear favorite between the Olympus E-PM2 and the Pentax 645D? Which camera is better? The listing below highlights the relative strengths of the two models.

Advantages of the Olympus PEN E-PM2:

• Better moiré control: Has an anti-alias filter to avoid artificial patterns to appear in images.
• Broader imaging potential: Can record not only still images but also 1080/30p movies.
• Fewer buttons to press: Is equipped with a touch-sensitive rear screen to facilitate handling.
• Faster burst: Shoots at higher frequency (8 vs 1.1 flaps/sec) to capture the decisive moment.
• More compact: Is smaller (110x64mm vs 156x117mm) and thus needs less room in the bag.
• Less heavy: Is lighter (by 1211g or 82 percent) and hence easier to carry around.
• Sharper images: Has hand-shake reducing image stabilization built-in.
• More legacy lens friendly: Can take a broad range of non-native lenses via adapters.
• Faster buffer clearing: Has an SD card interface that supports the UHS-I standard.
• More affordable: Was introduced into a lower priced category (95 percent cheaper at launch).
• More modern: Reflects 2 years and 6 months of technical progress since the 645D launch.

Reasons to prefer the Pentax 645D:

• More detail: Has more megapixels (39.5 vs 15.9MP), which boosts linear resolution by 58%.
• Maximized detail: Lacks an anti-alias filter to exploit the sensor's full resolution potential.
• Better image quality: Scores markedly higher (10 points) in the DXO overall evaluation.
• Richer colors: Generates noticeably more natural colors (1.9 bits more color depth).
• Better low-light sensitivity: Can shoot in dim conditions (0.4 stops ISO advantage).
• Easier framing: Has an optical 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).
• Easier time-lapse photography: Has an intervalometer built-in for low frequency shooting.
• Longer lasting: Gets more shots (800 versus 360) out of a single battery charge.
• Better sealing: Is splash and dust sealed for shooting in inclement weather conditions.
• Better studio light control: Has a PC Sync socket to connect to professional strobe lights.
• Greater peace of mind: Features a second card slot as a backup in case of memory card failure.
• More heavily discounted: Has been around for much longer (launched in March 2010).

If the count of individual advantages (bullet points above) is taken as a guide, the 645D emerges as the winner of the match-up (14 : 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 Olympus E-PM2 and the Pentax 645D 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 comparison of the spec-sheets of cameras can offer a general idea of their imaging potential, it remains incomplete and does no justice, for example, to the way the E-PM2 or the 645D perform in practice. 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 hands-on reviews by experts 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.		Olympus E-PM2	3/5	..	..	77/100	5/5	4.5/5	Sep 2012	499	ebay.com
2.		Pentax 645D	5/5	..	..	..	..	..	Mar 2010	9,995	ebay.com
3.		Canon 1D X	5/5	..	..	..	4.5/5	4.5/5	Oct 2011	6,799	ebay.com
4.		Canon 1D Mark IV	5/5	..	..	89/100	..	..	Oct 2009	4,999	ebay.com
5.		Leica S Typ 006	..	..	..	..	..	..	Sep 2012	21,950	ebay.com
6.		Nikon D3S	5/5	..	..	89/100	4.5/5	5/5	Oct 2009	5,199	ebay.com
7.		Olympus E-M10 II	4.5/5	+ +	..	80/100	5/5	5/5	Aug 2015	649	ebay.com
8.		Olympus E-M10	4/5	..	..	80/100	5/5	5/5	Jan 2014	699	ebay.com
9.		Olympus E-PL7	4/5	+	..	..	5/5	4/5	Aug 2014	599	ebay.com
10.		Olympus E-M1	5/5	+ +	..	84/100	4.5/5	4.5/5	Sep 2013	1,399	ebay.com
11.		Olympus E-P5	5/5	+ +	..	78/100	4.5/5	5/5	May 2013	999	ebay.com
12.		Olympus E-PL6	..	..	..	..	..	..	May 2013	599	ebay.com
13.		Olympus E-PL5	3/5	+ +	..	..	4.5/5	4.5/5	Sep 2012	599	ebay.com
14.		Olympus E-PL3	3/5	+ +	..	72/100	4.5/5	4/5	Jun 2011	599	ebay.com
15.		Olympus E-PM1	..	86/100	..	71/100	4.5/5	4.5/5	Jun 2011	499	ebay.com
16.		Panasonic G6	4/5	+ +	..	..	5/5	4.5/5	Apr 2013	599	ebay.com
17.		Pentax 645Z	5/5	..	3.5/5	..	4.5/5	5/5	Apr 2014	8,499	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 comparisons of ratings among very different cameras or across long time periods 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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