Nikon D3100 vs Olympus E-M5

The Nikon D3100 and the Olympus OM-D E-M5 are two digital cameras that were revealed to the public, respectively, in August 2010 and February 2012. The D3100 is a DSLR, while the E-M5 is a mirrorless interchangeable lens camera. The cameras are based on an APS-C (D3100) and a Four Thirds (E-M5) sensor. The Nikon has a resolution of 14.2 megapixels, whereas the Olympus provides 15.9 MP.

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

Headline Specifications

Nikon D3100		Olympus E-M5
Digital single lens reflex		Mirrorless system camera
Nikon F mount lenses		Micro Four Thirds lenses
14.2 MP – APS-C sensor		15.9 MP – Four Thirds sensor
1080/24p Video		1080/60i Video
ISO 100-3,200 (100 - 12,800)		ISO 200-25,600
Optical viewfinder		Electronic viewfinder (1440k dots)
3.0" LCD – 230k dots		3.0" LCD – 610k dots
Fixed screen (not touch-sensitive)		Tilting touchscreen
3 shutter flaps per second		9 shutter flaps per second
Lens stabilization only		In-body stabilization
not weather sealed		Weathersealed body
550 shots per battery charge		360 shots per battery charge
124 x 96 x 75 mm, 505 g		122 x 89 x 43 mm, 425 g

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Going beyond this snapshot of core features and characteristics, what are the differences between the Nikon D3100 and the Olympus OM-D E-M5? 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 Nikon D3100 and the Olympus E-M5. 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 D3100 can be obtained in two different colors (black, red), while the E-M5 is also available in two color-versions, but different ones (black, silver).

If the front view area (width x height) of the cameras is taken as an aggregate measure of their size, the Olympus E-M5 is notably smaller (9 percent) than the Nikon D3100. Moreover, the E-M5 is markedly lighter (16 percent) than the D3100. It is noteworthy in this context that the E-M5 is splash and dust-proof, while the D3100 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. A larger imaging sensor will tend to go along with bigger and heavier lenses, although exceptions exist. You can compare the optics available for the two cameras in the Nikon Lens Catalog (D3100) and the Micro Four Thirds Lens Catalog (E-M5). Mirrorless cameras, such as the E-M5, have moreover the advantage that they can use many lenses from other systems via adapters, as they have a relatively short flange to focal plane distance.

Concerning battery life, the D3100 gets 550 shots out of its Nikon EN-EL14 battery, while the E-M5 can take 360 images on a single charge of its Olympus BLN-1 power pack.

The adjacent table lists the principal physical characteristics of the two cameras alongside a wider set of alternatives. 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.		Nikon D3100	124 mm	96 mm	75 mm	505 g	550	n	Aug 2010	599	ebay.com
2.		Olympus E-M5	122 mm	89 mm	43 mm	425 g	360	Y	Feb 2012	1,299	ebay.com
3.		Nikon D40	124 mm	94 mm	64 mm	522 g	470	n	Nov 2006	499	ebay.com
4.		Nikon D40X	124 mm	94 mm	64 mm	522 g	520	n	Mar 2007	729	ebay.com
5.		Nikon D60	126 mm	94 mm	64 mm	522 g	500	n	Jan 2008	629	ebay.com
6.		Nikon D3000	126 mm	97 mm	64 mm	536 g	500	n	Jul 2009	599	ebay.com
7.		Nikon D3200	125 mm	96 mm	77 mm	505 g	540	n	Apr 2012	599	ebay.com
8.		Nikon D3300	124 mm	98 mm	76 mm	430 g	700	n	Jan 2014	499	ebay.com
9.		Nikon D3400	124 mm	98 mm	76 mm	445 g	1200	n	Aug 2016	499	ebay.com
10.		Nikon D5000	127 mm	104 mm	80 mm	590 g	510	n	Apr 2009	749	ebay.com
11.		Nikon D5100	128 mm	97 mm	79 mm	560 g	660	n	Apr 2011	749	ebay.com
12.		Nikon D5600	124 mm	97 mm	70 mm	465 g	970	n	Nov 2016	699	ebay.com
13.		Olympus E-M1	130 mm	94 mm	63 mm	497 g	350	Y	Sep 2013	1,399	ebay.com
14.		Olympus E-M5 II	124 mm	85 mm	45 mm	469 g	310	Y	Feb 2015	1,099	ebay.com
15.		Olympus E-M10	119 mm	82 mm	46 mm	396 g	320	n	Jan 2014	699	ebay.com
16.		Olympus E-M10 II	120 mm	83 mm	47 mm	390 g	320	n	Aug 2015	649	ebay.com
17.		Olympus E-P5	122 mm	69 mm	37 mm	420 g	330	n	May 2013	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 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 D3100 was launched at a markedly lower price (by 54 percent) than the E-M5, 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 size of the sensor inside a digital camera is one of the key determinants 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 are more costly to manufacture and tend to lead to bigger and heavier cameras and lenses.

Of the two cameras under consideration, the Nikon D3100 features an APS-C sensor and the Olympus E-M5 a Four Thirds sensor. The sensor area in the E-M5 is 37 percent smaller. As a result of these sensor size differences, the cameras have a format factor of, respectively, 1.5 and 2.0. The sensor in the D3100 has a native 3:2 aspect ratio, while the one in the E-M5 offers a 4:3 aspect.

Despite having a smaller sensor, the E-M5 offers a higher resolution of 15.9 megapixels, compared with 14.2 MP of the D3100. 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 5.01μm for the D3100). However, it should be noted that the E-M5 is a somewhat more recent model (by 1 year and 5 months) than the D3100, and its sensor might have benefitted from technological advances during this time that partly offset its pixel-size disadvantage.

The Nikon D3100 has a native sensitivity range from ISO 100 to ISO 3200, which can be extended to ISO 100-12800. The corresponding ISO settings for the Olympus OM-D E-M5 are ISO 200 to ISO 25600 (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.

Since 2007, DXO Mark has published sensor performance measurements that have been derived using a consistent methodology. This service is based on lab testing and assigns an overall score to each camera sensor, as well as ratings for dynamic range ("DXO Landscape"), color depth ("DXO Portrait"), and low-light sensitivity ("DXO Sports"). Of the two cameras under consideration, the E-M5 has a markedly higher DXO score than the D3100 (overall score 4 points higher), which will translate into better image quality. The advantage is based on 0.3 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.		Nikon D3100	APS-C	14.2	4608	3072	1080/24p	22.5	11.3	919	67
2.		Olympus E-M5	Four Thirds	15.9	4608	3456	1080/60i	22.8	12.3	826	71
3.		Nikon D40	APS-C	6.0	3008	2000	none	21.0	11.0	561	56
4.		Nikon D40X	APS-C	10.0	3872	2592	none	22.4	11.4	516	63
5.		Nikon D60	APS-C	10.0	3872	2592	none	22.5	11.4	562	65
6.		Nikon D3000	APS-C	10.0	3872	2592	none	22.3	11.1	563	62
7.		Nikon D3200	APS-C	24.1	6016	4000	1080/30p	24.1	13.2	1131	81
8.		Nikon D3300	APS-C	24.0	6000	4000	1080/60p	24.3	12.8	1385	82
9.		Nikon D3400	APS-C	24.0	6000	4000	1080/60p	24.8	13.9	1192	86
10.		Nikon D5000	APS-C	12.2	4288	2848	720/24p	22.7	12.5	868	72
11.		Nikon D5100	APS-C	16.1	4928	3264	1080/30p	23.5	13.6	1183	80
12.		Nikon D5600	APS-C	24.0	6000	4000	1080/60p	24.1	14.0	1306	84
13.		Olympus E-M1	Four Thirds	15.9	4608	3456	1080/30p	23.0	12.7	757	73
14.		Olympus E-M5 II	Four Thirds	15.9	4608	3456	1080/60p	23.0	12.5	842	73
15.		Olympus E-M10	Four Thirds	15.9	4608	3456	1080/30p	22.8	12.3	884	72
16.		Olympus E-M10 II	Four Thirds	15.9	4608	3456	1080/60p	23.1	12.5	842	73
17.		Olympus E-P5	Four Thirds	15.9	4608	3456	1080/30p	22.8	12.4	895	72

Many modern cameras cannot only take still pictures, but also record videos. The two cameras under consideration both have sensors whose read-out speed is fast enough to capture moving pictures, but the E-M5 provides a faster frame rate than the D3100. It can shoot movie footage at 1080/60i, while the Nikon is limited to 1080/24p.

Feature comparison

Apart from body and sensor, cameras can and do differ across a range of features. For example, the E-M5 has an electronic viewfinder (1440k dots), while the D3100 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 viewfinder in the E-M5 offers a wider field of view (100%) than the one in the D3100 (95%), so that a larger proportion of the captured image is visible in the finder. In addition, the viewfinder of the E-M5 has a higher magnification (0.58x vs 0.53x), so that the size of the image transmitted appears closer to the size seen with the naked human eye. The following table reports on some other key feature differences and similarities of the Nikon D3100, the Olympus E-M5, 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.		Nikon D3100	optical	n	3.0 / 230	fixed	n	1/4000s	3.0/s	Y	n
2.		Olympus E-M5	1440	n	3.0 / 610	tilting	Y	1/4000s	9.0/s	n	Y
3.		Nikon D40	optical	n	2.5 / 230	fixed	n	1/4000s	2.5/s	Y	n
4.		Nikon D40X	optical	n	2.5 / 230	fixed	n	1/4000s	3.0/s	Y	n
5.		Nikon D60	optical	n	2.5 / 230	fixed	n	1/4000s	3.0/s	Y	n
6.		Nikon D3000	optical	n	3.0 / 230	fixed	n	1/4000s	3.0/s	Y	n
7.		Nikon D3200	optical	n	3.0 / 921	fixed	n	1/4000s	4.0/s	Y	n
8.		Nikon D3300	optical	n	3.0 / 921	fixed	n	1/4000s	5.0/s	Y	n
9.		Nikon D3400	optical	n	3.0 / 921	fixed	n	1/4000s	5.0/s	Y	n
10.		Nikon D5000	optical	n	2.7 / 230	full-flex	n	1/4000s	4.0/s	Y	n
11.		Nikon D5100	optical	n	3.0 / 921	swivel	n	1/4000s	4.0/s	Y	n
12.		Nikon D5600	optical	n	3.2 / 1037	swivel	Y	1/4000s	5.0/s	Y	n
13.		Olympus E-M1	2360	n	3.0 / 1037	tilting	Y	1/8000s	10.0/s	n	Y
14.		Olympus E-M5 II	2360	n	3.0 / 1037	swivel	Y	1/8000s	10.0/s	n	Y
15.		Olympus E-M10	1440	n	3.0 / 1037	tilting	Y	1/4000s	8.0/s	Y	Y
16.		Olympus E-M10 II	2360	n	3.0 / 1040	tilting	Y	1/4000s	8.0/s	Y	Y
17.		Olympus E-P5	optional	n	3.0 / 1037	tilting	Y	1/8000s	9.0/s	Y	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 D3100 has one, while the E-M5 does not. While the built-in flash of the D3100 is not very powerful, it can at times be useful as a fill-in light.

Concerning the storage of imaging data, both the D3100 and the E-M5 write their files to SDXC cards. The E-M5 supports UHS-I cards (Ultra High Speed data transfer of up to 104 MB/s), while the D3100 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 Nikon D3100 and Olympus OM-D E-M5 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.		Nikon D3100	Y	mono / mono	-	-	mini	2.0	-	-	-
2.		Olympus E-M5	Y	stereo / mono	-	-	mini	2.0	-	-	-
3.		Nikon D40	Y	- / -	-	-	-	2.0	-	-	-
4.		Nikon D40X	Y	- / -	-	-	-	2.0	-	-	-
5.		Nikon D60	Y	- / -	-	-	-	2.0	-	-	-
6.		Nikon D3000	Y	- / -	-	-	-	2.0	-	-	-
7.		Nikon D3200	Y	mono / mono	Y	-	mini	2.0	-	-	-
8.		Nikon D3300	Y	mono / mono	Y	-	mini	2.0	-	-	-
9.		Nikon D3400	Y	mono / mono	-	-	mini	2.0	-	-	Y
10.		Nikon D5000	Y	mono / mono	-	-	mini	2.0	-	-	-
11.		Nikon D5100	Y	mono / mono	Y	-	mini	2.0	-	-	-
12.		Nikon D5600	Y	stereo / mono	Y	-	mini	2.0	Y	Y	Y
13.		Olympus E-M1	Y	stereo / mono	Y	-	micro	2.0	Y	-	-
14.		Olympus E-M5 II	Y	stereo / mono	Y	-	micro	2.0	Y	-	-
15.		Olympus E-M10	Y	stereo / mono	-	-	micro	2.0	Y	-	-
16.		Olympus E-M10 II	Y	stereo / mono	-	-	micro	2.0	Y	-	-
17.		Olympus E-P5	Y	stereo / mono	-	-	micro	2.0	Y	-	-

Both the D3100 and the E-M5 have been discontinued, but can regularly be found used on ebay. The D3100 was replaced by the Nikon D3200, while the E-M5 was followed by the Olympus E-M5 II. Further information on the features and operation of the D3100 and E-M5 can be found, respectively, in the Nikon D3100 Manual (free pdf) or the online Olympus E-M5 Manual.

Review summary

So what is the bottom line? Is there a clear favorite between the Nikon D3100 and the Olympus E-M5? Which camera is better? Below is a summary of the relative strengths of each of the two contestants.

Reasons to prefer the Nikon D3100:

• Brighter framing: Features an optical viewfinder for clear, lag-free composition.
• Longer lasting: Can take more shots (550 versus 360) on a single battery charge.
• Easier fill-in: Is equipped with a small onboard flash to brighten deep shadow areas.
• More affordable: Was introduced into a lower priced category (54 percent cheaper at launch).
• More heavily discounted: Has been on the market for longer (launched in August 2010).

Arguments in favor of the Olympus OM-D E-M5:

• Better image quality: Scores markedly higher (4 points) in the DXO overall evaluation.
• More dynamic range: Captures a broader range of light and dark details (1 EV of extra DR).
• Better video: Provides higher movie framerates (1080/60i versus 1080/24p).
• More framing info: Has an electronic viewfinder that displays shooting data.
• More complete view: Has a viewfinder with a larger field of view (100% vs 95%).
• Larger viewfinder image: Features a viewfinder with a higher magnification (0.58x vs 0.53x).
• More detailed LCD: Has a higher resolution rear screen (610k vs 230k dots).
• More flexible LCD: Has a tilting screen for odd-angle shots in landscape orientation.
• Fewer buttons to press: Has a touchscreen to facilitate handling and shooting adjustments.
• Faster burst: Shoots at higher frequency (9 vs 3 flaps/sec) to capture the decisive moment.
• Less heavy: Has a lower weight (by 80g or 16 percent) and is thus easier to take along.
• Better sealing: Is splash and dust sealed for shooting in inclement weather conditions.
• Sharper images: Has stabilization technology built-in to reduce the impact of hand-shake.
• More legacy lens friendly: Can use many non-native lenses via adapters.
• Faster buffer clearing: Has an SD card interface that supports the UHS-I standard.
• More modern: Was introduced somewhat (1 year and 5 months) more recently.

If the count of relative strengths (bullet points above) is taken as a measure, the E-M5 is the clear winner of the contest (16 : 5 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 Nikon D3100 and the Olympus E-M5 place the cameras among the top in their class? Find out in the latest Best DSLR Camera and Best Mirrorless Interchangeable Lens Camera listings whether the two cameras rank among the cream of the crop.

In any case, while the comparison of technical specifications can provide a useful overview of the capabilities of different cameras, it remains incomplete and does no justice, for example, to the way the D3100 or the E-M5 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 hands-on reviews by experts are important. 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.		Nikon D3100	5/5	+ +	..	72/100	4.5/5	4.5/5	Aug 2010	599	ebay.com
2.		Olympus E-M5	4/5	+ +	..	80/100	4.5/5	5/5	Feb 2012	1,299	ebay.com
3.		Nikon D40	..	81/100	..	+ +	o	4.5/5	Nov 2006	499	ebay.com
4.		Nikon D40X	..	79/100	..	+ +	4/5	4/5	Mar 2007	729	ebay.com
5.		Nikon D60	..	80/100	..	+ +	4/5	4.5/5	Jan 2008	629	ebay.com
6.		Nikon D3000	..	+	..	72/100	4/5	4.5/5	Jul 2009	599	ebay.com
7.		Nikon D3200	5/5	+ +	..	73/100	4.5/5	4.5/5	Apr 2012	599	ebay.com
8.		Nikon D3300	3/5	+	..	77/100	4.5/5	4.5/5	Jan 2014	499	ebay.com
9.		Nikon D3400	4/5	+	4/5	76/100	4/5	4.5/5	Aug 2016	499	ebay.com
10.		Nikon D5000	..	+ +	..	75/100	4/5	4.5/5	Apr 2009	749	ebay.com
11.		Nikon D5100	5/5	+ +	..	76/100	4.5/5	4.5/5	Apr 2011	749	ebay.com
12.		Nikon D5600	4/5	..	4/5	79/100	4.5/5	4/5	Nov 2016	699	ebay.com
13.		Olympus E-M1	5/5	+ +	..	84/100	4.5/5	4.5/5	Sep 2013	1,399	ebay.com
14.		Olympus E-M5 II	5/5	+ +	4.5/5	81/100	5/5	5/5	Feb 2015	1,099	ebay.com
15.		Olympus E-M10	4/5	..	..	80/100	5/5	5/5	Jan 2014	699	ebay.com
16.		Olympus E-M10 II	4.5/5	+ +	..	80/100	5/5	5/5	Aug 2015	649	ebay.com
17.		Olympus E-P5	5/5	+ +	..	78/100	4.5/5	5/5	May 2013	999	ebay.com
Note: (+ +) highly recommended; (+) recommended; (o) reviewed; (..) not available.

The review scores listed above should be treated with care, though. The assessments were made in relation to similar cameras of the same technological generation. 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. 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

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