Sony Alpha SLT-A37 vs. Nikon D3100

Comparison

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Alpha SLT-A37 image
vs
D3100 image
Sony Alpha SLT-A37 Nikon D3100
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Megapixels
16.10
14.20
Max. image resolution
4912 x 3264
4608 x 3072

Sensor

Sensor type
CMOS
CMOS
Sensor size
23.5 x 15.6 mm
23.1 x 15.4 mm
Sensor resolution
4930 x 3265
4616 x 3077
Diagonal
28.21 mm
27.76 mm
Sensor size comparison
Sensor size is generally a good indicator of the quality of the camera. Sensors can vary greatly in size. As a general rule, the bigger the sensor, the better the image quality.

Bigger sensors are more effective because they have more surface area to capture light. An important factor when comparing digital cameras is also camera generation. Generally, newer sensors will outperform the older.

Learn more about sensor sizes »

Actual sensor size

Note: Actual size is set to screen → change »
vs
1.03 : 1
(ratio)
Sony Alpha SLT-A37 Nikon D3100
Surface area:
366.60 mm² vs 355.74 mm²
Difference: 10.86 mm² (3%)
Alpha SLT-A37 sensor is slightly bigger than D3100 sensor (only 3% difference).
Note: You are comparing cameras of different generations. There is a 2 year gap between Sony Alpha SLT-A37 (2012) and Nikon D3100 (2010). All things being equal, newer sensor generations generally outperform the older.
Pixel pitch
4.77 µm
5 µm
Pixel pitch tells you the distance from the center of one pixel (photosite) to the center of the next. It tells you how close the pixels are to each other.

The bigger the pixel pitch, the further apart they are and the bigger each pixel is. Bigger pixels tend to have better signal to noise ratio and greater dynamic range.
Difference: 0.23 µm (5%)
Pixel pitch of D3100 is approx. 5% higher than pixel pitch of Alpha SLT-A37.
Pixel area
22.75 µm²
25 µm²
Pixel or photosite area affects how much light per pixel can be gathered. The larger it is the more light can be collected by a single pixel.

Larger pixels have the potential to collect more photons, resulting in greater dynamic range, while smaller pixels provide higher resolutions (more detail) for a given sensor size.
Relative pixel sizes:
vs
Pixel area difference: 2.25 µm² (10%)
A pixel on Nikon D3100 sensor is approx. 10% bigger than a pixel on Sony Alpha SLT-A37.
Pixel density
4.4 MP/cm²
3.99 MP/cm²
Pixel density tells you how many million pixels fit or would fit in one square cm of the sensor.

Higher pixel density means smaller pixels and lower pixel density means larger pixels.
Difference: 0.41 µm (10%)
Sony Alpha SLT-A37 has approx. 10% higher pixel density than Nikon D3100.
To learn about the accuracy of these numbers, click here.

Specs

Sony Alpha SLT-A37
Nikon D3100
Crop factor
1.53
1.56
Total megapixels
16.70
14.80
Effective megapixels
16.10
14.20
Optical zoom
Digital zoom
Yes
No
ISO sensitivity
Auto, 100, 200, 400, 800, 1600, 3200, 6400, 12800, 25600
Auto, 100, 200, 400, 800, 1600, 3200 (12800 with boost)
RAW
Manual focus
Normal focus range
Macro focus range
Focal length (35mm equiv.)
Aperture priority
Yes
Yes
Max. aperture
Max. aperture (35mm equiv.)
n/a
n/a
Metering
Multi, Center-weighted, Spot
Multi, Center-weighted, Average
Exposure compensation
±3 EV (in 1/3 EV steps)
±5 EV (in 1/3 EV steps)
Shutter priority
Yes
Yes
Min. shutter speed
30 sec
30 sec
Max. shutter speed
1/4000 sec
1/4000 sec
Built-in flash
External flash
Viewfinder
Electronic
Optical (pentamirror)
White balance presets
6
12
Screen size
2.6"
3"
Screen resolution
230,400 dots
230,000 dots
Video capture
Max. video resolution
1920x1080 (24p)
Storage types
SD/SDHC/SDXC/Memory Stick Pro Duo/ Pro-HG Duo
SDHC, SDXC, Secure Digital
USB
USB 2.0 (480 Mbit/sec)
USB 2.0 (480 Mbit/sec)
HDMI
Wireless
GPS
Battery
Rechargeable NP-FW50 battery
Lithium-Ion EN-EL14 rechargeable battery
Weight
506 g
505 g
Dimensions
124 x 92 x 85 mm
124 x 96 x 75 mm
Year
2012
2010



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Diagonal

Diagonal is calculated by the use of Pythagorean theorem:
Diagonal =  w² + h²
where w = sensor width and h = sensor height

Sony Alpha SLT-A37 diagonal

w = 23.50 mm
h = 15.60 mm
Diagonal =  23.50² + 15.60²   = 28.21 mm

Nikon D3100 diagonal

w = 23.10 mm
h = 15.40 mm
Diagonal =  23.10² + 15.40²   = 27.76 mm


Surface area

Surface area is calculated by multiplying the width and the height of a sensor.

Alpha SLT-A37 sensor area

Width = 23.50 mm
Height = 15.60 mm

Surface area = 23.50 × 15.60 = 366.60 mm²

D3100 sensor area

Width = 23.10 mm
Height = 15.40 mm

Surface area = 23.10 × 15.40 = 355.74 mm²


Pixel pitch

Pixel pitch is the distance from the center of one pixel to the center of the next measured in micrometers (µm). It can be calculated with the following formula:
Pixel pitch =   sensor width in mm  × 1000
sensor resolution width in pixels

Alpha SLT-A37 pixel pitch

Sensor width = 23.50 mm
Sensor resolution width = 4930 pixels
Pixel pitch =   23.50  × 1000  = 4.77 µm
4930

D3100 pixel pitch

Sensor width = 23.10 mm
Sensor resolution width = 4616 pixels
Pixel pitch =   23.10  × 1000  = 5 µm
4616


Pixel area

The area of one pixel can be calculated by simply squaring the pixel pitch:
Pixel area = pixel pitch²

You could also divide sensor surface area with effective megapixels:
Pixel area =   sensor surface area in mm²
effective megapixels

Alpha SLT-A37 pixel area

Pixel pitch = 4.77 µm

Pixel area = 4.77² = 22.75 µm²

D3100 pixel area

Pixel pitch = 5 µm

Pixel area = 5² = 25 µm²


Pixel density

Pixel density can be calculated with the following formula:
Pixel density =  ( sensor resolution width in pixels )² / 1000000
sensor width in cm

One could also use this formula:
Pixel density =   effective megapixels × 1000000  / 10000
sensor surface area in mm²

Alpha SLT-A37 pixel density

Sensor resolution width = 4930 pixels
Sensor width = 2.35 cm

Pixel density = (4930 / 2.35)² / 1000000 = 4.4 MP/cm²

D3100 pixel density

Sensor resolution width = 4616 pixels
Sensor width = 2.31 cm

Pixel density = (4616 / 2.31)² / 1000000 = 3.99 MP/cm²


Sensor resolution

Sensor resolution is calculated from sensor size and effective megapixels. It's slightly higher than maximum (not interpolated) image resolution which is usually stated on camera specifications. Sensor resolution is used in pixel pitch, pixel area, and pixel density formula. For sake of simplicity, we're going to calculate it in 3 stages.

1. First we need to find the ratio between horizontal and vertical length by dividing the former with the latter (aspect ratio). It's usually 1.33 (4:3) or 1.5 (3:2), but not always.

2. With the ratio (r) known we can calculate the X from the formula below, where X is a vertical number of pixels:
(X × r) × X = effective megapixels × 1000000    →   
X =  effective megapixels × 1000000
r
3. To get sensor resolution we then multiply X with the corresponding ratio:

Resolution horizontal: X × r
Resolution vertical: X

Alpha SLT-A37 sensor resolution

Sensor width = 23.50 mm
Sensor height = 15.60 mm
Effective megapixels = 16.10
r = 23.50/15.60 = 1.51
X =  16.10 × 1000000  = 3265
1.51
Resolution horizontal: X × r = 3265 × 1.51 = 4930
Resolution vertical: X = 3265

Sensor resolution = 4930 x 3265

D3100 sensor resolution

Sensor width = 23.10 mm
Sensor height = 15.40 mm
Effective megapixels = 14.20
r = 23.10/15.40 = 1.5
X =  14.20 × 1000000  = 3077
1.5
Resolution horizontal: X × r = 3077 × 1.5 = 4616
Resolution vertical: X = 3077

Sensor resolution = 4616 x 3077


Crop factor

Crop factor or focal length multiplier is calculated by dividing the diagonal of 35 mm film (43.27 mm) with the diagonal of the sensor.
Crop factor =   43.27 mm
sensor diagonal in mm


Alpha SLT-A37 crop factor

Sensor diagonal in mm = 28.21 mm
Crop factor =   43.27  = 1.53
28.21

D3100 crop factor

Sensor diagonal in mm = 27.76 mm
Crop factor =   43.27  = 1.56
27.76

35 mm equivalent aperture

Equivalent aperture (in 135 film terms) is calculated by multiplying lens aperture with crop factor (a.k.a. focal length multiplier).

Alpha SLT-A37 equivalent aperture

Aperture is a lens characteristic, so it's calculated only for fixed lens cameras. If you want to know the equivalent aperture for Sony Alpha SLT-A37, take the aperture of the lens you're using and multiply it with crop factor.

Crop factor for Sony Alpha SLT-A37 is 1.53

D3100 equivalent aperture

Aperture is a lens characteristic, so it's calculated only for fixed lens cameras. If you want to know the equivalent aperture for Nikon D3100, take the aperture of the lens you're using and multiply it with crop factor.

Crop factor for Nikon D3100 is 1.56

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