Casio Exilim EX-Z250 vs. Samsung ST50

Comparison

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Exilim EX-Z250 image
vs
ST50 image
Casio Exilim EX-Z250 Samsung ST50
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Megapixels
9.10
12.20
Max. image resolution
3456 x 2592

Sensor

Sensor type
CCD
CCD
Sensor size
1/2.5" (~ 5.75 x 4.32 mm)
1/2.33" (~ 6.08 x 4.56 mm)
Sensor resolution
3479 x 2616
4029 x 3029
Diagonal
7.19 mm
7.60 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 : 1.12
(ratio)
Casio Exilim EX-Z250 Samsung ST50
Surface area:
24.84 mm² vs 27.72 mm²
Difference: 2.88 mm² (12%)
ST50 sensor is approx. 1.12x bigger than Z250 sensor.
Pixel pitch
1.65 µm
1.51 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: 0.14 µm (9%)
Pixel pitch of Z250 is approx. 9% higher than pixel pitch of ST50.
Pixel area
2.72 µm²
2.28 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: 0.44 µm² (19%)
A pixel on Casio Z250 sensor is approx. 19% bigger than a pixel on Samsung ST50.
Pixel density
36.61 MP/cm²
43.91 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: 7.3 µm (20%)
Samsung ST50 has approx. 20% higher pixel density than Casio Z250.
To learn about the accuracy of these numbers, click here.



Specs

Casio Z250
Samsung ST50
Crop factor
6.02
5.69
Total megapixels
9.30
Effective megapixels
9.10
Optical zoom
4x
Yes
Digital zoom
Yes
Yes
ISO sensitivity
Auto, 64, 100, 200, 400, 800, 1600, 3200
Auto, 80, 100, 200, 400, 800, 1600, 3200
RAW
Manual focus
Normal focus range
40 cm
Macro focus range
10 cm
Focal length (35mm equiv.)
28 - 112 mm
Aperture priority
No
No
Max. aperture
f2.6 - f5.9
f3.0 - f5.6
Max. aperture (35mm equiv.)
f15.7 - f35.5
f17.1 - f31.9
Metering
Centre weighted, Multi-pattern, Spot
Centre weighted
Exposure compensation
±2 EV (in 1/3 EV steps)
±2 EV (in 1/3 EV steps)
Shutter priority
No
No
Min. shutter speed
4 sec
Max. shutter speed
1/2000 sec
Built-in flash
External flash
Viewfinder
None
None
White balance presets
7
Screen size
3"
2.7"
Screen resolution
230,400 dots
230,000 dots
Video capture
Max. video resolution
Storage types
MultiMedia, SDHC, Secure Digital
SDHC, Secure Digital
USB
USB 2.0 (480 Mbit/sec)
USB 2.0 (480 Mbit/sec)
HDMI
Wireless
GPS
Battery
Lithium-Ion rechargeable
Weight
119 g
Dimensions
96.7 x 57.3 x 19.9 mm
Year
2008
2009




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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

Casio Z250 diagonal

The diagonal of Z250 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

Samsung ST50 diagonal

The diagonal of ST50 sensor is not 1/2.33 or 0.43" (10.9 mm) as you might expect, but approximately two thirds of that value - 7.6 mm. If you want to know why, see sensor sizes.

w = 6.08 mm
h = 4.56 mm
Diagonal =  6.08² + 4.56²   = 7.60 mm


Surface area

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

Z250 sensor area

Width = 5.75 mm
Height = 4.32 mm

Surface area = 5.75 × 4.32 = 24.84 mm²

ST50 sensor area

Width = 6.08 mm
Height = 4.56 mm

Surface area = 6.08 × 4.56 = 27.72 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

Z250 pixel pitch

Sensor width = 5.75 mm
Sensor resolution width = 3479 pixels
Pixel pitch =   5.75  × 1000  = 1.65 µm
3479

ST50 pixel pitch

Sensor width = 6.08 mm
Sensor resolution width = 4029 pixels
Pixel pitch =   6.08  × 1000  = 1.51 µm
4029


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

Z250 pixel area

Pixel pitch = 1.65 µm

Pixel area = 1.65² = 2.72 µm²

ST50 pixel area

Pixel pitch = 1.51 µm

Pixel area = 1.51² = 2.28 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

Z250 pixel density

Sensor resolution width = 3479 pixels
Sensor width = 0.575 cm

Pixel density = (3479 / 0.575)² / 1000000 = 36.61 MP/cm²

ST50 pixel density

Sensor resolution width = 4029 pixels
Sensor width = 0.608 cm

Pixel density = (4029 / 0.608)² / 1000000 = 43.91 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

Z250 sensor resolution

Sensor width = 5.75 mm
Sensor height = 4.32 mm
Effective megapixels = 9.10
r = 5.75/4.32 = 1.33
X =  9.10 × 1000000  = 2616
1.33
Resolution horizontal: X × r = 2616 × 1.33 = 3479
Resolution vertical: X = 2616

Sensor resolution = 3479 x 2616

ST50 sensor resolution

Sensor width = 6.08 mm
Sensor height = 4.56 mm
Effective megapixels = 12.20
r = 6.08/4.56 = 1.33
X =  12.20 × 1000000  = 3029
1.33
Resolution horizontal: X × r = 3029 × 1.33 = 4029
Resolution vertical: X = 3029

Sensor resolution = 4029 x 3029


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


Z250 crop factor

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

ST50 crop factor

Sensor diagonal in mm = 7.60 mm
Crop factor =   43.27  = 5.69
7.60

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).

Z250 equivalent aperture

Crop factor = 6.02
Aperture = f2.6 - f5.9

35-mm equivalent aperture = (f2.6 - f5.9) × 6.02 = f15.7 - f35.5

ST50 equivalent aperture

Crop factor = 5.69
Aperture = f3.0 - f5.6

35-mm equivalent aperture = (f3.0 - f5.6) × 5.69 = f17.1 - f31.9

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