Canon PowerShot A400 vs. Sony Cyber-shot DSC-P31

Comparison

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PowerShot A400 image
vs
Cyber-shot DSC-P31 image
Canon PowerShot A400 Sony Cyber-shot DSC-P31
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Megapixels
3.10
2.11
Max. image resolution
2048 x 1536
1600 x 1200

Sensor

Sensor type
CCD
CCD
Sensor size
1/3.2" (~ 4.5 x 3.37 mm)
1/2.7" (~ 5.33 x 4 mm)
Sensor resolution
2038 x 1521
1676 x 1260
Diagonal
5.62 mm
6.66 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 : 1.41
(ratio)
Canon PowerShot A400 Sony Cyber-shot DSC-P31
Surface area:
15.17 mm² vs 21.32 mm²
Difference: 6.15 mm² (41%)
P31 sensor is approx. 1.41x bigger than A400 sensor.
Note: You are comparing cameras of different generations. There is a 2 year gap between Canon A400 (2004) and Sony P31 (2002). All things being equal, newer sensor generations generally outperform the older.
Pixel pitch
2.21 µm
3.18 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: 0.97 µm (44%)
Pixel pitch of P31 is approx. 44% higher than pixel pitch of A400.
Pixel area
4.88 µm²
10.11 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: 5.23 µm² (107%)
A pixel on Sony P31 sensor is approx. 107% bigger than a pixel on Canon A400.
Pixel density
20.51 MP/cm²
9.89 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: 10.62 µm (107%)
Canon A400 has approx. 107% higher pixel density than Sony P31.
To learn about the accuracy of these numbers, click here.



Specs

Canon A400
Sony P31
Crop factor
7.7
6.5
Total megapixels
3.30
Effective megapixels
3.10
Optical zoom
2.2x
1x
Digital zoom
Yes
Yes
ISO sensitivity
Auto, 50, 100, 200, 400
Auto, 100, 200, 400
RAW
Manual focus
Normal focus range
50 cm
10 cm
Macro focus range
5 cm
10 cm
Focal length (35mm equiv.)
45 - 100 mm
33 mm
Aperture priority
No
No
Max. aperture
f2.8 - f4.9
f2.8
Max. aperture (35mm equiv.)
f21.6 - f37.7
f18.2
Metering
Multi, Center-weighted, Spot
Centre weighted, Multi-segment, Spot
Exposure compensation
±2 EV (in 1/3 EV steps)
±2 EV (in 1/3 EV steps)
Shutter priority
No
No
Min. shutter speed
1 sec
2 sec
Max. shutter speed
1/1500 sec
1/1000 sec
Built-in flash
External flash
Viewfinder
Optical (tunnel)
Optical (tunnel)
White balance presets
5
6
Screen size
1.5"
1.6"
Screen resolution
115,000 dots
61,000 dots
Video capture
Max. video resolution
Storage types
SD/MMC card
Memory Stick
USB
USB 1.0
USB 1.0
HDMI
Wireless
GPS
Battery
AA (2) batteries (NiMH recommended)
AA (2) batteries (NiMH rechargables included)
Weight
255 g
231 g
Dimensions
107 x 53 x 37 mm
106 x 58 x 40 mm
Year
2004
2002




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vs

Diagonal

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

Canon A400 diagonal

The diagonal of A400 sensor is not 1/3.2 or 0.31" (7.9 mm) as you might expect, but approximately two thirds of that value - 5.62 mm. If you want to know why, see sensor sizes.

w = 4.50 mm
h = 3.37 mm
Diagonal =  4.50² + 3.37²   = 5.62 mm

Sony P31 diagonal

The diagonal of P31 sensor is not 1/2.7 or 0.37" (9.4 mm) as you might expect, but approximately two thirds of that value - 6.66 mm. If you want to know why, see sensor sizes.

w = 5.33 mm
h = 4.00 mm
Diagonal =  5.33² + 4.00²   = 6.66 mm


Surface area

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

A400 sensor area

Width = 4.50 mm
Height = 3.37 mm

Surface area = 4.50 × 3.37 = 15.17 mm²

P31 sensor area

Width = 5.33 mm
Height = 4.00 mm

Surface area = 5.33 × 4.00 = 21.32 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

A400 pixel pitch

Sensor width = 4.50 mm
Sensor resolution width = 2038 pixels
Pixel pitch =   4.50  × 1000  = 2.21 µm
2038

P31 pixel pitch

Sensor width = 5.33 mm
Sensor resolution width = 1676 pixels
Pixel pitch =   5.33  × 1000  = 3.18 µm
1676


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

A400 pixel area

Pixel pitch = 2.21 µm

Pixel area = 2.21² = 4.88 µm²

P31 pixel area

Pixel pitch = 3.18 µm

Pixel area = 3.18² = 10.11 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

A400 pixel density

Sensor resolution width = 2038 pixels
Sensor width = 0.45 cm

Pixel density = (2038 / 0.45)² / 1000000 = 20.51 MP/cm²

P31 pixel density

Sensor resolution width = 1676 pixels
Sensor width = 0.533 cm

Pixel density = (1676 / 0.533)² / 1000000 = 9.89 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

A400 sensor resolution

Sensor width = 4.50 mm
Sensor height = 3.37 mm
Effective megapixels = 3.10
r = 4.50/3.37 = 1.34
X =  3.10 × 1000000  = 1521
1.34
Resolution horizontal: X × r = 1521 × 1.34 = 2038
Resolution vertical: X = 1521

Sensor resolution = 2038 x 1521

P31 sensor resolution

Sensor width = 5.33 mm
Sensor height = 4.00 mm
Effective megapixels = 2.11
r = 5.33/4.00 = 1.33
X =  2.11 × 1000000  = 1260
1.33
Resolution horizontal: X × r = 1260 × 1.33 = 1676
Resolution vertical: X = 1260

Sensor resolution = 1676 x 1260


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


A400 crop factor

Sensor diagonal in mm = 5.62 mm
Crop factor =   43.27  = 7.7
5.62

P31 crop factor

Sensor diagonal in mm = 6.66 mm
Crop factor =   43.27  = 6.5
6.66

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).

A400 equivalent aperture

Crop factor = 7.7
Aperture = f2.8 - f4.9

35-mm equivalent aperture = (f2.8 - f4.9) × 7.7 = f21.6 - f37.7

P31 equivalent aperture

Crop factor = 6.5
Aperture = f2.8

35-mm equivalent aperture = (f2.8) × 6.5 = f18.2

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