Nikon D3100 vs Sony A900

The Nikon D3100 and the Sony Alpha A900 are two digital cameras that were revealed to the public, respectively, in August 2010 and September 2008. Both are DSLR (Digital Single Lens Reflex) cameras that are based on an APS-C (D3100) and a full frame (A900) sensor. The Nikon has a resolution of 14.2 megapixels, whereas the Sony provides 24.4 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 A900
Digital single lens reflex		Digital single lens reflex
Nikon F mount lenses		Sony A mount lenses
14.2 MP – APS-C sensor		24.4 MP – Full Frame sensor
1080/24p Video		no Video
ISO 100-3,200 (100 - 12,800)		ISO 200-3,200 (100 - 6,400)
Optical viewfinder		Optical viewfinder
3.0" LCD – 230k dots		3.0" LCD – 922k dots
Fixed screen (not touch-sensitive)		Fixed screen (not touch-sensitive)
3 shutter flaps per second		5 shutter flaps per second
Lens stabilization only		In-body stabilization
not weather sealed		Weathersealed body
550 shots per battery charge		880 shots per battery charge
124 x 96 x 75 mm, 505 g		156 x 117 x 82 mm, 895 g

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Going beyond this snapshot of core features and characteristics, what are the differences between the Nikon D3100 and the Sony Alpha A900? 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 Sony A900. 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 measures are rounded to the nearest millimeter.

The D3100 can be obtained in two different colors (black, red), while the A900 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 A900 is considerably larger (53 percent) than the Nikon D3100. Moreover, the A900 is substantially heavier (77 percent) than the D3100. It is noteworthy in this context that the A900 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. 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 D3100 gets 550 shots out of its Nikon EN-EL14 battery, while the A900 can take 880 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.		Nikon D3100	124 mm	96 mm	75 mm	505 g	550	n	Aug 2010	599	ebay.com
2.		Sony A900	156 mm	117 mm	82 mm	895 g	880	Y	Sep 2008	2,999	ebay.com
3.		Canon 5D Mark II	152 mm	114 mm	75 mm	850 g	850	Y	Sep 2008	3,499	ebay.com
4.		Nikon D5600	124 mm	97 mm	70 mm	465 g	970	n	Nov 2016	699	ebay.com
5.		Nikon D3400	124 mm	98 mm	76 mm	445 g	1200	n	Aug 2016	499	ebay.com
6.		Nikon D3300	124 mm	98 mm	76 mm	430 g	700	n	Jan 2014	499	ebay.com
7.		Nikon D3200	125 mm	96 mm	77 mm	505 g	540	n	Apr 2012	599	ebay.com
8.		Nikon D5100	128 mm	97 mm	79 mm	560 g	660	n	Apr 2011	749	ebay.com
9.		Nikon D3000	126 mm	97 mm	64 mm	536 g	500	n	Jul 2009	599	ebay.com
10.		Nikon D5000	127 mm	104 mm	80 mm	590 g	510	n	Apr 2009	749	ebay.com
11.		Nikon D60	126 mm	94 mm	64 mm	522 g	500	n	Jan 2008	629	ebay.com
12.		Nikon D40X	124 mm	94 mm	64 mm	522 g	520	n	Mar 2007	729	ebay.com
13.		Nikon D40	124 mm	94 mm	64 mm	522 g	470	n	Nov 2006	499	ebay.com
14.		Panasonic S1	149 mm	110 mm	97 mm	1017 g	400	Y	Feb 2019	2,499	amazon.com
15.		Sony A99 II	143 mm	104 mm	76 mm	849 g	490	Y	Sep 2016	3,199	ebay.com
16.		Sony A99	147 mm	111 mm	78 mm	812 g	500	Y	Sep 2012	2,799	ebay.com
17.		Sony A850	156 mm	117 mm	82 mm	895 g	880	Y	Aug 2009	1,999	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 listed launch prices provide an indication of the market segment that the manufacturer of the cameras have been targeting. The D3100 was launched at a markedly lower price (by 80 percent) than the A900, 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.

Sensor comparison

The size of the imaging sensor is a crucial determinant 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. Further, a large sensor camera will give the photographer additional creative options when using shallow depth-of-field to isolate a subject from its background. On the downside, larger sensors tend to be more expensive and lead to bigger and heavier cameras and lenses.

Of the two cameras under consideration, the Nikon D3100 features an APS-C sensor and the Sony A900 a full frame sensor. The sensor area in the A900 is 142 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.

With 24.4MP, the A900 offers a higher resolution than the D3100 (14.2MP), but the A900 nevertheless has larger individual pixels (pixel pitch of 5.94μm versus 5.01μm for the D3100) due to its larger sensor. However, the D3100 is a somewhat more recent model (by 1 year and 11 months) than the A900, 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 A900 implies greater flexibility for cropping images or the possibility to print larger pictures. The maximum print size of the A900 for good quality output (200 dots per inch) amounts to 30.2 x 20.2 inches or 76.8 x 51.2 cm, for very good quality (250 dpi) 24.2 x 16.1 inches or 61.4 x 41 cm, and for excellent quality (300 dpi) 20.2 x 13.4 inches or 51.2 x 34.1 cm. The corresponding values for the Nikon D3100 are 23 x 15.4 inches or 58.5 x 39 cm for good quality, 18.4 x 12.3 inches or 46.8 x 31.2 cm for very good quality, and 15.4 x 10.2 inches or 39 x 26 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 A900 are ISO 200 to ISO 3200, with the possibility to increase the ISO range to 100-6400.

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 A900 offers substantially better image quality than the D3100 (overall score 12 points higher). The advantage is based on 1.2 bits higher color depth, 1 EV in additional dynamic range, and 0.6 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 A900	Full Frame	24.4	6048	4032	none	23.7	12.3	1431	79
3.		Canon 5D Mark II	Full Frame	21.0	5616	3744	1080/30p	23.7	11.9	1815	79
4.		Nikon D5600	APS-C	24.0	6000	4000	1080/60p	24.1	14.0	1306	84
5.		Nikon D3400	APS-C	24.0	6000	4000	1080/60p	24.8	13.9	1192	86
6.		Nikon D3300	APS-C	24.0	6000	4000	1080/60p	24.3	12.8	1385	82
7.		Nikon D3200	APS-C	24.1	6016	4000	1080/30p	24.1	13.2	1131	81
8.		Nikon D5100	APS-C	16.1	4928	3264	1080/30p	23.5	13.6	1183	80
9.		Nikon D3000	APS-C	10.0	3872	2592	none	22.3	11.1	563	62
10.		Nikon D5000	APS-C	12.2	4288	2848	720/24p	22.7	12.5	868	72
11.		Nikon D60	APS-C	10.0	3872	2592	none	22.5	11.4	562	65
12.		Nikon D40X	APS-C	10.0	3872	2592	none	22.4	11.4	516	63
13.		Nikon D40	APS-C	6.0	3008	2000	none	21.0	11.0	561	56
14.		Panasonic S1	Full Frame	24.0	6000	4000	4K/60p	25.2	14.5	3333	95
15.		Sony A99 II	Full Frame	42.2	7952	5304	4K/30p	25.4	13.4	2317	92
16.		Sony A99	Full Frame	24.0	6000	4000	1080/60p	25.0	14.0	1555	89
17.		Sony A850	Full Frame	24.4	6048	4032	none	23.8	12.2	1415	79

Many modern cameras are not only capable of taking still images, but can also record movies. The D3100 indeed provides movie recording capabilities, while the A900 does not. The highest resolution format that the D3100 can use is 1080/24p.

Feature comparison

Apart from body and sensor, cameras can and do differ across a variety of features. The D3100 and the A900 are similar in the sense that both have an optical viewfinder. The latter is useful for getting a clear image for framing even in brightly lit environments. The viewfinder in the A900 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 A900 has a higher magnification (0.74x 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 A900, 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.		Sony A900	optical	Y	3.0 / 922	fixed	n	1/8000s	5.0/s	n	Y
3.		Canon 5D Mark II	optical	Y	3.0 / 920	fixed	n	1/8000s	3.9/s	n	n
4.		Nikon D5600	optical	n	3.2 / 1037	swivel	Y	1/4000s	5.0/s	Y	n
5.		Nikon D3400	optical	n	3.0 / 921	fixed	n	1/4000s	5.0/s	Y	n
6.		Nikon D3300	optical	n	3.0 / 921	fixed	n	1/4000s	5.0/s	Y	n
7.		Nikon D3200	optical	n	3.0 / 921	fixed	n	1/4000s	4.0/s	Y	n
8.		Nikon D5100	optical	n	3.0 / 921	swivel	n	1/4000s	4.0/s	Y	n
9.		Nikon D3000	optical	n	3.0 / 230	fixed	n	1/4000s	3.0/s	Y	n
10.		Nikon D5000	optical	n	2.7 / 230	full-flex	n	1/4000s	4.0/s	Y	n
11.		Nikon D60	optical	n	2.5 / 230	fixed	n	1/4000s	3.0/s	Y	n
12.		Nikon D40X	optical	n	2.5 / 230	fixed	n	1/4000s	3.0/s	Y	n
13.		Nikon D40	optical	n	2.5 / 230	fixed	n	1/4000s	2.5/s	Y	n
14.		Panasonic S1	5760	Y	3.2 / 2100	full-flex	Y	1/8000s	9.0/s	n	Y
15.		Sony A99 II	2400	Y	3.0 / 1229	full-flex	n	1/8000s	12.0/s	n	Y
16.		Sony A99	2359	Y	3.0 / 1229	full-flex	n	1/8000s	6.0/s	n	Y
17.		Sony A850	optical	Y	3.0 / 922	fixed	n	1/8000s	3.0/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 D3100 has one, while the A900 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 D3100 writes its imaging data to SDXC cards, while the A900 uses Compact Flash or Memory Stick PRO Duo cards. The A900 features dual card slots, which can be very useful in case a memory card fails. In contrast, the D3100 only has one slot.

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 A900 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.		Sony A900	Y	- / -	-	-	mini	2.0	-	-	-
3.		Canon 5D Mark II	Y	mono / mono	Y	-	mini	2.0	-	-	-
4.		Nikon D5600	Y	stereo / mono	Y	-	mini	2.0	Y	Y	Y
5.		Nikon D3400	Y	mono / mono	-	-	mini	2.0	-	-	Y
6.		Nikon D3300	Y	mono / mono	Y	-	mini	2.0	-	-	-
7.		Nikon D3200	Y	mono / mono	Y	-	mini	2.0	-	-	-
8.		Nikon D5100	Y	mono / mono	Y	-	mini	2.0	-	-	-
9.		Nikon D3000	Y	- / -	-	-	-	2.0	-	-	-
10.		Nikon D5000	Y	mono / mono	-	-	mini	2.0	-	-	-
11.		Nikon D60	Y	- / -	-	-	-	2.0	-	-	-
12.		Nikon D40X	Y	- / -	-	-	-	2.0	-	-	-
13.		Nikon D40	Y	- / -	-	-	-	2.0	-	-	-
14.		Panasonic S1	Y	stereo / mono	Y	Y	full	3.1	Y	-	Y
15.		Sony A99 II	Y	stereo / mono	Y	Y	micro	2.0	Y	Y	Y
16.		Sony A99	Y	stereo / mono	Y	Y	mini	2.0	-	-	-
17.		Sony A850	Y	- / -	-	-	mini	2.0	-	-	-

Studio photographers will appreciate that the Sony A900 (unlike the D3100) features a PC Sync socket, so that professional strobe lights can be controlled by the camera.

Both the D3100 and the A900 have been discontinued, but can regularly be found used on ebay. The A900 was replaced by the Sony A99, while the D3100 was followed by the Nikon D3200. Further information on the features and operation of the D3100 and A900 can be found, respectively, in the Nikon D3100 Manual (free pdf) or the online Sony A900 Manual.

Review summary

So what conclusions can be drawn? Is there a clear favorite between the Nikon D3100 and the Sony A900? Which camera is better? Below is a summary of the relative strengths of each of the two contestants.

Arguments in favor of the Nikon D3100:

• Broader imaging potential: Can record not only still images but also 1080/24p movies.
• More compact: Is smaller (124x96mm vs 156x117mm) and thus needs less room in the bag.
• Less heavy: Is lighter (by 390g or 44 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 (80 percent cheaper at launch).
• More modern: Is somewhat more recent (announced 1 year and 11 months after the A900).

Reasons to prefer the Sony Alpha A900:

• More detail: Has more megapixels (24.4 vs 14.2MP), which boosts linear resolution by 31%.
• Better image quality: Scores substantially higher (12 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 (1 EV of extra DR).
• Better low-light sensitivity: Can shoot in dim conditions (0.6 stops ISO advantage).
• 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 (0.74x vs 0.53x).
• Easier setting verification: Features a control panel on top to check shooting parameters.
• More detailed LCD: Has a higher resolution rear screen (922k vs 230k dots).
• Faster shutter: Has higher mechanical shutter speed (1/8000s vs 1/4000s) to freeze action.
• Faster burst: Shoots at higher frequency (5 vs 3 flaps/sec) to capture the decisive moment.
• Longer lasting: Gets more shots (880 versus 550) out of a single battery charge.
• 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.
• 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 on the market for longer (launched in September 2008).

If the number of relative strengths (bullet points above) is taken as a guide, the A900 is the clear winner of the contest (17 : 6 points). However, the pertinence of the various camera strengths will differ across photographers, so that you might want to weigh individual camera traits according to their importance for your own imaging needs before making a camera decision. A professional sports photographer will view the differences between cameras in a way that diverges from the perspective of a street photog, and a person interested in family portraits has distinct needs from a landscape 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 A900 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 comparison of the spec-sheets of cameras can offer a general idea of their imaging potential, it remains partial and cannot reveal, for example, the shooting experience and imaging performance when actually working with the D3100 or the A900. 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.		Nikon D3100	5/5	+ +	..	72/100	4.5/5	4.5/5	Aug 2010	599	ebay.com
2.		Sony A900	..	+ +	..	+ +	4.5/5	5/5	Sep 2008	2,999	ebay.com
3.		Canon 5D Mark II	4/5	91/100	..	79/100	4/5	..	Sep 2008	3,499	ebay.com
4.		Nikon D5600	4/5	..	4/5	79/100	4.5/5	4/5	Nov 2016	699	ebay.com
5.		Nikon D3400	4/5	+	4/5	76/100	4/5	4.5/5	Aug 2016	499	ebay.com
6.		Nikon D3300	3/5	+	..	77/100	4.5/5	4.5/5	Jan 2014	499	ebay.com
7.		Nikon D3200	5/5	+ +	..	73/100	4.5/5	4.5/5	Apr 2012	599	ebay.com
8.		Nikon D5100	5/5	+ +	..	76/100	4.5/5	4.5/5	Apr 2011	749	ebay.com
9.		Nikon D3000	..	+	..	72/100	4/5	4.5/5	Jul 2009	599	ebay.com
10.		Nikon D5000	..	+ +	..	75/100	4/5	4.5/5	Apr 2009	749	ebay.com
11.		Nikon D60	..	80/100	..	+ +	4/5	4.5/5	Jan 2008	629	ebay.com
12.		Nikon D40X	..	79/100	..	+ +	4/5	4/5	Mar 2007	729	ebay.com
13.		Nikon D40	..	81/100	..	+ +	o	4.5/5	Nov 2006	499	ebay.com
14.		Panasonic S1	4.5/5	+ +	4.5/5	88/100	4.5/5	4/5	Feb 2019	2,499	amazon.com
15.		Sony A99 II	..	..	4.5/5	85/100	4.5/5	4.5/5	Sep 2016	3,199	ebay.com
16.		Sony A99	5/5	..	..	84/100	4.5/5	4.5/5	Sep 2012	2,799	ebay.com
17.		Sony A850	3/5	..	..	75/100	..	4.5/5	Aug 2009	1,999	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 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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Check A900 offers at
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Other camera comparisons

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