Canon PowerShot SD790 IS vs. Canon PowerShot SD400

Comparison

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PowerShot SD790 IS image
vs
PowerShot SD400 image
Canon PowerShot SD790 IS Canon PowerShot SD400
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Megapixels
10.00
5.00
Max. image resolution
3648 x 2736
2592 x 1944

Sensor

Sensor type
CCD
CCD
Sensor size
1/2.3" (~ 6.16 x 4.62 mm)
1/2.5" (~ 5.75 x 4.32 mm)
Sensor resolution
3647 x 2742
2579 x 1939
Diagonal
7.70 mm
7.19 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
1.15 : 1
(ratio)
Canon PowerShot SD790 IS Canon PowerShot SD400
Surface area:
28.46 mm² vs 24.84 mm²
Difference: 3.62 mm² (15%)
SD790 IS sensor is approx. 1.15x bigger than SD400 sensor.
Note: You are comparing cameras of different generations. There is a 3 year gap between Canon SD790 IS (2008) and Canon SD400 (2005). All things being equal, newer sensor generations generally outperform the older.
Pixel pitch
1.69 µm
2.23 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: 0.54 µm (32%)
Pixel pitch of SD400 is approx. 32% higher than pixel pitch of SD790 IS.
Pixel area
2.86 µm²
4.97 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: 2.11 µm² (74%)
A pixel on Canon SD400 sensor is approx. 74% bigger than a pixel on Canon SD790 IS.
Pixel density
35.05 MP/cm²
20.12 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: 14.93 µm (74%)
Canon SD790 IS has approx. 74% higher pixel density than Canon SD400.
To learn about the accuracy of these numbers, click here.



Specs

Canon SD790 IS
Canon SD400
Crop factor
5.62
6.02
Total megapixels
10.30
5.20
Effective megapixels
10.00
5.00
Optical zoom
3x
3x
Digital zoom
Yes
Yes
ISO sensitivity
Auto, High Auto, 80 ,100, 200, 400, 800, 1600
Auto, 50, 100, 200, 400
RAW
Manual focus
Normal focus range
30 cm
50 cm
Macro focus range
3 cm
3 cm
Focal length (35mm equiv.)
35 - 105 mm
35 - 105 mm
Aperture priority
No
No
Max. aperture
f2.8 - f4.9
f2.8 - f4.9
Max. aperture (35mm equiv.)
f15.7 - f27.5
f16.9 - f29.5
Metering
Multi, Center-weighted, Spot
Multi, Center-weighted, Spot
Exposure compensation
±2 EV (in 1/3 EV steps)
±2 EV (in 1/3 EV steps)
Shutter priority
No
No
Min. shutter speed
15 sec
15 sec
Max. shutter speed
1/1600 sec
1/1500 sec
Built-in flash
External flash
Viewfinder
None
Optical (tunnel)
White balance presets
5
5
Screen size
3"
2"
Screen resolution
230,000 dots
118,000 dots
Video capture
Max. video resolution
Storage types
SD/SDHC/MMC card
SD card
USB
USB 2.0 (480 Mbit/sec)
USB 2.0 (480 Mbit/sec)
HDMI
Wireless
GPS
Battery
Lithium-Ion NB-5L battery
Lithium-Ion NB-4L battery
Weight
195 g
150 g
Dimensions
92 x 57 x 21 mm
86 x 53 x 21 mm
Year
2008
2005




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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

Canon SD790 IS diagonal

The diagonal of SD790 IS sensor is not 1/2.3 or 0.43" (11 mm) as you might expect, but approximately two thirds of that value - 7.7 mm. If you want to know why, see sensor sizes.

w = 6.16 mm
h = 4.62 mm
Diagonal =  6.16² + 4.62²   = 7.70 mm

Canon SD400 diagonal

The diagonal of SD400 sensor is not 1/2.5 or 0.4" (10.2 mm) as you might expect, but approximately two thirds of that value - 7.19 mm. If you want to know why, see sensor sizes.

w = 5.75 mm
h = 4.32 mm
Diagonal =  5.75² + 4.32²   = 7.19 mm


Surface area

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

SD790 IS sensor area

Width = 6.16 mm
Height = 4.62 mm

Surface area = 6.16 × 4.62 = 28.46 mm²

SD400 sensor area

Width = 5.75 mm
Height = 4.32 mm

Surface area = 5.75 × 4.32 = 24.84 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

SD790 IS pixel pitch

Sensor width = 6.16 mm
Sensor resolution width = 3647 pixels
Pixel pitch =   6.16  × 1000  = 1.69 µm
3647

SD400 pixel pitch

Sensor width = 5.75 mm
Sensor resolution width = 2579 pixels
Pixel pitch =   5.75  × 1000  = 2.23 µm
2579


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

SD790 IS pixel area

Pixel pitch = 1.69 µm

Pixel area = 1.69² = 2.86 µm²

SD400 pixel area

Pixel pitch = 2.23 µm

Pixel area = 2.23² = 4.97 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

SD790 IS pixel density

Sensor resolution width = 3647 pixels
Sensor width = 0.616 cm

Pixel density = (3647 / 0.616)² / 1000000 = 35.05 MP/cm²

SD400 pixel density

Sensor resolution width = 2579 pixels
Sensor width = 0.575 cm

Pixel density = (2579 / 0.575)² / 1000000 = 20.12 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

SD790 IS sensor resolution

Sensor width = 6.16 mm
Sensor height = 4.62 mm
Effective megapixels = 10.00
r = 6.16/4.62 = 1.33
X =  10.00 × 1000000  = 2742
1.33
Resolution horizontal: X × r = 2742 × 1.33 = 3647
Resolution vertical: X = 2742

Sensor resolution = 3647 x 2742

SD400 sensor resolution

Sensor width = 5.75 mm
Sensor height = 4.32 mm
Effective megapixels = 5.00
r = 5.75/4.32 = 1.33
X =  5.00 × 1000000  = 1939
1.33
Resolution horizontal: X × r = 1939 × 1.33 = 2579
Resolution vertical: X = 1939

Sensor resolution = 2579 x 1939


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


SD790 IS crop factor

Sensor diagonal in mm = 7.70 mm
Crop factor =   43.27  = 5.62
7.70

SD400 crop factor

Sensor diagonal in mm = 7.19 mm
Crop factor =   43.27  = 6.02
7.19

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).

SD790 IS equivalent aperture

Crop factor = 5.62
Aperture = f2.8 - f4.9

35-mm equivalent aperture = (f2.8 - f4.9) × 5.62 = f15.7 - f27.5

SD400 equivalent aperture

Crop factor = 6.02
Aperture = f2.8 - f4.9

35-mm equivalent aperture = (f2.8 - f4.9) × 6.02 = f16.9 - f29.5

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