Nikon D3100 vs Sony A7S III

The Nikon D3100 and the Sony Alpha 7S III are two digital cameras that were announced, respectively, in August 2010 and July 2020. The D3100 is a DSLR, while the A7S III is a mirrorless interchangeable lens camera. The cameras are based on an APS-C (D3100) and a full frame (A7S III) sensor. The Nikon has a resolution of 14.2 megapixels, whereas the Sony provides 12 MP.

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

Headline Specifications

Nikon D3100		Sony A7S III
Digital single lens reflex		Mirrorless system camera
Nikon F mount lenses		Sony E mount lenses
14.2 MP, APS-C Sensor		12 MP, Full Frame Sensor
1080/24p Video		4K/120p Video
ISO 100-3,200 (100 - 12,800)		ISO 80-102,400 (40 - 409,600)
Optical viewfinder		Electronic viewfinder (9440k dots)
3.0 LCD, 230k dots		3.0 LCD, 1440k dots
Fixed screen (not touch-sensitive)		Swivel touchscreen
3 shutter flaps per second		10 shutter flaps per second
Lens stabilization only		In-body stabilization
not weather sealed		Weathersealed body
550 shots per battery charge		600 shots per battery charge
124 x 96 x 75 mm, 505 g		127 x 97 x 81 mm, 699 g

Going beyond this snapshot of core features and characteristics, what are the differences between the Nikon D3100 and the Sony Alpha 7S III? 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 Nikon D3100 and the Sony A7S III 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 width, height and depth dimensions are rounded to the nearest millimeter.

The D3100 can be obtained in two different colors (black, red), while the A7S III 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 A7S III is somewhat larger (3 percent) than the Nikon D3100. Moreover, the A7S III is substantially heavier (38 percent) than the D3100. It is noteworthy in this context that the A7S III 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 Sony FE Lens Catalog (A7S III). Mirrorless cameras, such as the A7S III, 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 EN-EL14 battery, while the A7S III can take 600 images on a single charge of its NP-FZ100 power pack. The power pack in the A7S III can be charged via the USB port, which can be very convenient when travelling.

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.		Nikon D3100	124 mm	96 mm	75 mm	505 g	550	n	Aug 2010	599
2.		Sony A7S III	127 mm	97 mm	81 mm	699 g	600	Y	Jul 2020	3,499
3.		Nikon D3200	125 mm	96 mm	77 mm	505 g	540	n	Apr 2012	599
4.		Nikon D5100	128 mm	97 mm	79 mm	560 g	660	n	Apr 2011	749
5.		Nikon D7000	132 mm	105 mm	77 mm	780 g	1050	Y	Sep 2010	1,499
6.		Nikon D3000	126 mm	97 mm	64 mm	536 g	500	n	Jul 2009	599
7.		Nikon D5000	127 mm	104 mm	80 mm	590 g	510	n	Apr 2009	749
8.		Nikon D60	126 mm	94 mm	64 mm	522 g	500	n	Jan 2008	629
9.		Nikon D40X	124 mm	94 mm	64 mm	522 g	520	n	Mar 2007	729
10.		Nikon D40	124 mm	94 mm	64 mm	522 g	470	n	Nov 2006	499
11.		Sony A7R IV	129 mm	96 mm	78 mm	665 g	670	Y	Jul 2019	3,499
12.		Sony A7R III	127 mm	96 mm	74 mm	650 g	650	Y	Oct 2017	3,199
13.		Sony A9	127 mm	96 mm	63 mm	673 g	650	Y	Apr 2017	4,499
14.		Sony A7R II	127 mm	96 mm	60 mm	625 g	290	Y	Jun 2015	3,199
15.		Sony A7S II	127 mm	96 mm	60 mm	627 g	370	Y	Sep 2015	2,999
16.		Sony NEX-5N	111 mm	59 mm	38 mm	269 g	460	n	Aug 2011	699
17.		Sony NEX-C3	110 mm	60 mm	33 mm	225 g	400	n	Jun 2011	599
Notes: 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 83 percent) than the A7S III, which puts it into a different market segment. Normally, street prices remain initially close to the MSRP, but after a couple of months, the first discounts appear. 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. 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 associated with larger, more expensive camera bodies and lenses.

Of the two cameras under consideration, the Nikon D3100 features an APS-C sensor and the Sony A7S III a full frame sensor. The sensor area in the A7S III is 138 percent bigger. As a result of these sensor size differences, the cameras have a format factor of, respectively, 1.5 and 1.0. Both cameras have a native aspect ratio (sensor width to sensor height) of 3:2.

Despite having a smaller sensor, the Nikon D3100 offers a higher resolution of 14.2 megapixels, compared with 12 MP of the Sony A7S III. 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 5.01μm versus 8.40μm for the A7S III). Moreover, it should be noted that the A7S III is much more recent (by 9 years and 11 months) than the D3100, and its sensor will have benefitted from technological advances during this time that further enhance the light gathering capacity of its pixel-units.

The resolution advantage of the Nikon D3100 implies greater flexibility for cropping images or the possibility to print larger pictures. The maximum print size of the D3100 for good quality output (200 dots per inch) amounts to 23 x 15.4 inches or 58.5 x 39 cm, for very good quality (250 dpi) 18.4 x 12.3 inches or 46.8 x 31.2 cm, and for excellent quality (300 dpi) 15.4 x 10.2 inches or 39 x 26 cm. The corresponding values for the Sony A7S III are 21.2 x 14.2 inches or 53.8 x 36 cm for good quality, 17 x 11.3 inches or 43.1 x 28.8 cm for very good quality, and 14.1 x 9.4 inches or 35.9 x 24 cm for excellent quality prints.

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 Sony Alpha 7S III are ISO 80 to ISO 102400, with the possibility to increase the ISO range to 40-409600.

For many cameras, data on sensor performance has been reported by DXO Mark. This service assesses and scores the color depth ("DXO Portrait"), dynamic range ("DXO Landscape"), and low-light sensitivity ("DXO Sports") of camera sensors, and also publishes an overall camera score. Of the two cameras under consideration, the A7S III offers substantially better image quality than the D3100 (overall score 19 points higher). The advantage is based on 1.2 bits higher color depth, 2.6 EV in additional dynamic range, and 1.5 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.		Nikon D3100	APS-C	14.2	4608	3072	1080/24p	22.5	11.3	919	67
2.		Sony A7S III	Full Frame	12.0	4240	2832	4K/120p	23.7	13.9	2520	86
3.		Nikon D3200	APS-C	24.1	6016	4000	1080/30p	24.1	13.2	1131	81
4.		Nikon D5100	APS-C	16.1	4928	3264	1080/30p	23.5	13.6	1183	80
5.		Nikon D7000	APS-C	16.1	4928	3264	10800/24p	23.5	13.9	1167	80
6.		Nikon D3000	APS-C	10.0	3872	2592	none	22.3	11.1	563	62
7.		Nikon D5000	APS-C	12.2	4288	2848	720/24p	22.7	12.5	868	72
8.		Nikon D60	APS-C	10.0	3872	2592	none	22.5	11.4	562	65
9.		Nikon D40X	APS-C	10.0	3872	2592	none	22.4	11.4	516	63
10.		Nikon D40	APS-C	6.0	3008	2000	none	21.0	11.0	561	56
11.		Sony A7R IV	Full Frame	60.2	9504	6336	4K/30p	26.0	14.8	3344	99
12.		Sony A7R III	Full Frame	42.2	7952	5304	4K/30p	26.0	14.7	3523	100
13.		Sony A9	Full Frame	24.0	6000	4000	4K/30p	24.9	13.3	3517	92
14.		Sony A7R II	Full Frame	42.2	7952	5304	4K/30p	26.0	13.9	3434	98
15.		Sony A7S II	Full Frame	12.0	4240	2832	4K/30p	23.6	13.3	2993	85
16.		Sony NEX-5N	APS-C	16.0	4912	3264	1080/60i	23.6	12.7	1079	77
17.		Sony NEX-C3	APS-C	16.0	4912	3264	720/30p	22.7	12.2	1083	73

Many modern cameras cannot only take still pictures, but also record videos. Both cameras under consideration have a sensor with sufficiently fast read-out times for moving pictures, but the A7S III provides a better video resolution than the D3100. It can shoot movie footage at 4K/120p, while the Nikon is limited to 1080/24p.

Feature comparison

Beyond body and sensor, cameras can and do differ across a range of features. For example, the A7S III has an electronic viewfinder (9440k 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 A7S III 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 A7S III has a higher magnification (0.91x 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 Sony A7S III, and comparable cameras.

Core Features

		Camera Model	Viewfinder (Type or 000 dots)	Control Panel (yes/no)	LCD Size (inch)	LCD Resolution (000 dots)	LCD Attach- ment	Touch Screen (yes/no)	Mech Shutter Speed	Shutter Flaps (1/sec)	Built-in Flash (yes/no)	Built-in Image Stab
1.		Nikon D3100	optical	n	3.0	230	fixed	n	1/4000s	3.0	Y	n
2.		Sony A7S III	9440	n	3.0	1440	swivel	Y	1/8000s	10.0	n	Y
3.		Nikon D3200	optical	n	3.0	921	fixed	n	1/4000s	4.0	Y	n
4.		Nikon D5100	optical	n	3.0	921	swivel	n	1/4000s	4.0	Y	n
5.		Nikon D7000	optical	Y	3.0	921	fixed	n	1/8000s	6.0	Y	n
6.		Nikon D3000	optical	n	3.0	230	fixed	n	1/4000s	3.0	Y	n
7.		Nikon D5000	optical	n	2.7	230	full-flex	n	1/4000s	4.0	Y	n
8.		Nikon D60	optical	n	2.5	230	fixed	n	1/4000s	3.0	Y	n
9.		Nikon D40X	optical	n	2.5	230	fixed	n	1/4000s	3.0	Y	n
10.		Nikon D40	optical	n	2.5	230	fixed	n	1/4000s	2.5	Y	n
11.		Sony A7R IV	5760	n	3.0	1440	tilting	Y	1/8000s	10.0	n	Y
12.		Sony A7R III	3686	n	3.0	1440	tilting	Y	1/8000s	10.0	n	Y
13.		Sony A9	3686	n	3.0	1440	tilting	Y	1/8000s	20.0	n	Y
14.		Sony A7R II	2400	n	3.0	1229	tilting	n	1/8000s	5.0	n	Y
15.		Sony A7S II	2400	n	3.0	1229	tilting	n	1/8000s	5.0	n	Y
16.		Sony NEX-5N	optional	n	3.0	920	tilting	Y	1/4000s	10.0	n	n
17.		Sony NEX-C3	optional	n	3.0	920	tilting	n	1/4000s	5.5	n	n

One difference between the cameras concerns the presence of an on-board flash. The D3100 has one, while the A7S III 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.

The reported shutter speed information refers to the use of the mechanical shutter. Yet, some cameras only have an electronic shutter, while others have an electronic shutter in addition to a mechanical one. In fact, the A7S III is one of those camera that have an additional electronic shutter, which makes completely silent shooting possible. However, this mode is less suitable for photographing moving objects (risk of rolling shutter) or shooting under artificial light sources (risk of flickering).

The D3100 writes its imaging data to SDXC cards, while the A7S III uses CFexpress or SDXC cards. The A7S III features dual card slots, which can be very useful in case a memory card fails. In contrast, the D3100 only has one slot. The A7S III supports UHS-II cards (on both slots), 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 Sony Alpha 7S III 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 Microphone	Internal 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.		Sony A7S III	Y	stereo	mono	Y	Y	full	3.2	Y	-	Y
3.		Nikon D3200	Y	mono	mono	Y	-	mini	2.0	-	-	-
4.		Nikon D5100	Y	mono	mono	Y	-	mini	2.0	-	-	-
5.		Nikon D7000	Y	mono	mono	Y	-	mini	2.0	-	-	-
6.		Nikon D3000	Y	-	-	-	-	-	2.0	-	-	-
7.		Nikon D5000	Y	mono	mono	-	-	mini	2.0	-	-	-
8.		Nikon D60	Y	-	-	-	-	-	2.0	-	-	-
9.		Nikon D40X	Y	-	-	-	-	-	2.0	-	-	-
10.		Nikon D40	Y	-	-	-	-	-	2.0	-	-	-
11.		Sony A7R IV	Y	stereo	mono	Y	Y	micro	3.1	Y	Y	Y
12.		Sony A7R III	Y	stereo	mono	Y	Y	micro	3.1	Y	Y	Y
13.		Sony A9	Y	stereo	mono	Y	Y	micro	2.0	Y	Y	Y
14.		Sony A7R II	Y	stereo	mono	Y	Y	micro	2.0	Y	Y	-
15.		Sony A7S II	Y	stereo	mono	Y	Y	micro	2.0	Y	Y	-
16.		Sony NEX-5N	Y	stereo	mono	-	-	mini	2.0	-	-	-
17.		Sony NEX-C3	Y	stereo	mono	-	-	mini	2.0	-	-	-

It is notable that the A7S III offers wifi support, which can be a very convenient means to transfer image data to an off-camera location. In contrast, the D3100 does not provide wifi capability.

The A7S III is a recent model that features in the current product line-up of Sony. In contrast, the D3100 has been discontinued (but can be found pre-owned on eBay). As a replacement in the same line of cameras, the D3100 was succeeded by the Nikon D3200. Further information on the two cameras (e.g. user guides, manuals), as well as related accessories, can be found on the official Nikon and Sony websites.

Review summary

So what conclusions can be drawn? Which of the two cameras – the Nikon D3100 or the Sony A7S III – has the upper hand? Is one clearly better than the other? A synthesis of the relative strong points of each of the models is listed below.

Arguments in favor of the Nikon D3100:

• More detail: Offers more megapixels (14.2 vs 12MP) with a 9% higher linear resolution.
• Brighter framing: Features an optical viewfinder for clear, lag-free composition.
• Less heavy: Is lighter (by 194g or 28 percent) and hence easier to carry around.
• Easier fill-in: Is equipped with a small onboard flash to brighten deep shadow areas.
• More affordable: Was introduced into a lower priced category (83 percent cheaper at launch).
• More heavily discounted: Has been available for much longer (launched in August 2010).

Reasons to prefer the Sony Alpha 7S III:

• Better image quality: Scores substantially higher (19 points) in the DXO overall evaluation.
• Richer colors: Generates noticeably more natural colors (1.2 bits more color depth).
• More dynamic range: Captures a broader range of light and dark details (2.6 EV of extra DR).
• Better low-light sensitivity: Can shoot in dim conditions (1.5 stops ISO advantage).
• Better video: Provides higher definition movie capture (4K/120p vs 1080/24p).
• Better sound: Can connect to an external microphone for higher quality sound recording.
• Better sound control: Has a headphone port that enables audio monitoring while recording.
• 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 (0.91x vs 0.53x).
• More detailed LCD: Has a higher resolution rear screen (1440k vs 230k dots).
• More flexible LCD: Has a swivel screen for odd-angle shots in portrait or landscape orientation.
• Fewer buttons to press: Has a touchscreen to facilitate handling and shooting adjustments.
• 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 (10 vs 3 flaps/sec) to capture the decisive moment.
• Less disturbing: Has an electronic shutter option for completely silent shooting.
• Easier travel charging: Can be conveniently charged via its USB port.
• 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 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 Ultra High Speed (UHS-II) SDXC cards on both slots.
• More modern: Reflects 9 years and 11 months of technical progress since the D3100 launch.

If the number of relative strengths (bullet points above) is taken as a guide, the A7S III is the clear winner of the contest (28 : 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 wedding photographer will view the differences between cameras in a way that diverges from the perspective of a travel photog, and a person interested in cityscapes has distinct needs from a macro 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 Sony A7S III 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 says little about, for example, the shooting experience and imaging performance of the D3100 and the A7S III in practical situations. 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], 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	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
2.		Sony A7S III	..	+ +	91/100	4.5/5	5/5	Jul 2020	3,499
3.		Nikon D3200	5/5	+ +	73/100	4.5/5	4.5/5	Apr 2012	599
4.		Nikon D5100	5/5	+ +	76/100	4.5/5	4.5/5	Apr 2011	749
5.		Nikon D7000	4/5	..	80/100	4.5/5	4.5/5	Sep 2010	1,499
6.		Nikon D3000	..	+	72/100	4/5	4.5/5	Jul 2009	599
7.		Nikon D5000	..	+ +	75/100	4/5	4.5/5	Apr 2009	749
8.		Nikon D60	..	80/100	+ +	4/5	4.5/5	Jan 2008	629
9.		Nikon D40X	..	79/100	+ +	4/5	4/5	Mar 2007	729
10.		Nikon D40	..	81/100	+ +	o	4.5/5	Nov 2006	499
11.		Sony A7R IV	5/5	+	91/100	4.5/5	5/5	Jul 2019	3,499
12.		Sony A7R III	..	+ +	90/100	4.5/5	5/5	Oct 2017	3,199
13.		Sony A9	5/5	+ +	89/100	5/5	5/5	Apr 2017	4,499
14.		Sony A7R II	5/5	+ +	90/100	5/5	5/5	Jun 2015	3,199
15.		Sony A7S II	5/5	+	..	4.5/5	5/5	Sep 2015	2,999
16.		Sony NEX-5N	3/5	+ +	79/100	4.5/5	4.5/5	Aug 2011	699
17.		Sony NEX-C3	3/5	+ +	74/100	4.5/5	4/5	Jun 2011	599
Notes: (+ +) 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. Thus, a score needs to be put into the context of the launch date and the launch price of the camera, and rating-comparisons among cameras that span long time periods or concern very differently equipped models make little sense. It should also be noted that some of the review sites have over time altered the way they render their verdicts.

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 use the search menu below. There is also a set of direct links to comparison reviews that other users of the CAM-parator app explored.

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Specifications: Nikon D3100 vs Sony A7S III

Below is a side-by-side comparison of the specs of the two cameras to facilitate a quick review of their differences and common features.

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