Olympus C-21


Brand: Olympus
Model: C-21
Megapixels: 1.90
Sensor: 1/2" (~ 6.4 x 4.8 mm)
Price: check here »

Sensor info

Olympus C-21 comes with a 1/2" (~ 6.4 x 4.8 mm) CCD sensor, which has a diagonal of 8.00 mm (0.31") and a surface area of 30.72 mm².
8.00 mm
Surface area
30.7 mm²
Pixel pitch
4.03 µm
Pixel area
16.24 µm²
Pixel density
6.16 MP/cm²
If you want to know about the accuracy of these numbers, click here.

Actual sensor size

Note: Actual size is set to screen → change »
This is the actual size of the C-21 sensor: ~6.4 x 4.8 mm
The sensor has a surface area of 30.7 mm². There are approx. 1,900,000 photosites (pixels) on this area. Pixel pitch, which is a measure of the distance between pixels, is 4.03 µm. Pixel pitch tells you the distance from the center of one pixel (photosite) to the center of the next.

Pixel or photosite area is 16.24 µm². The larger the photosite, the more light it can capture and the more information can be recorded.

Pixel density tells you how many million pixels fit or would fit in one square cm of the sensor. Olympus C-21 has a pixel density of 6.16 MP/cm².

These numbers are important in terms of assessing the overall quality of a digital camera. Generally, the bigger (and newer) the sensor, pixel pitch and photosite area, and the smaller the pixel density, the better the camera. If you want to see how C-21 compares to other cameras, click here.


Brand: Olympus
Model: C-21
Effective megapixels: 1.90
Total megapixels: 2.10
Sensor size: 1/2" (~ 6.4 x 4.8 mm)
Sensor type: CCD
Sensor resolution: 1589 x 1195
Max. image resolution: 1600 x 1200
Crop factor: 5.41
Optical zoom: 1x
Digital zoom: Yes
ISO: Auto, 100,200, 400
RAW support:
Manual focus:
Normal focus range: 60 cm
Macro focus range: 20 cm
Focal length (35mm equiv.): 38 mm
Aperture priority: No
Max aperture: f2.4
Max. aperture (35mm equiv.): f13
Depth of field: simulate →
Metering: Centre weighted
Exposure Compensation: ±2 EV (in 1/3 EV steps)
Shutter priority: No
Min. shutter speed: 1/2 sec
Max. shutter speed: 1/750 sec
Built-in flash:
External flash:
Viewfinder: Optical (tunnel)
White balance presets: 5
Screen size: 1.8"
Screen resolution: 114,000 dots
Video capture:
Storage types: SmartMedia
USB: USB 1.0
Battery: AA (4) batteries (NiMH recommended)
Weight: 240 g
Dimensions: 107 x 62 x 36 mm
Year: 1999

Compare C-21 with another camera



The diagonal of C-21 sensor is not 1/2 or 0.5" (12.7 mm) as you might expect, but approximately two thirds of that value - 0.31" (8 mm). If you want to know why, see sensor sizes.

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

Olympus C-21 diagonal:

w = 6.40 mm
h = 4.80 mm
Diagonal =  6.40² + 4.80²   = 8.00 mm

Surface area

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

Width = 6.40 mm
Height = 4.80 mm

Surface area = 6.40 × 4.80 = 30.72 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

Olympus C-21 pixel pitch:

Sensor width = 6.40 mm
Sensor resolution width = 1589 pixels
Pixel pitch =   6.40  × 1000  = 4.03 µm

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

Olympus C-21 pixel area:

Pixel pitch = 4.03 µm

Pixel area = 4.03² = 16.24 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

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

Olympus C-21 pixel density:

Sensor resolution width = 1589 pixels
Sensor width = 0.64 cm

Pixel density = (1589 / 0.64)² / 1000000 = 6.16 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
3. To get sensor resolution we then multiply X with the corresponding ratio:

Resolution horizontal: X × r
Resolution vertical: X

Olympus C-21 sensor resolution:

Sensor width = 6.40 mm
Sensor height = 4.80 mm
Effective megapixels = 1.90
r = 6.40/4.80 = 1.33
X =  1.90 × 1000000  = 1195
Resolution horizontal: X × r = 1195 × 1.33 = 1589
Resolution vertical: X = 1195

Sensor resolution = 1589 x 1195

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

Olympus C-21 crop factor:

Sensor diagonal = 8.00 mm
Crop factor =   43.27  = 5.41

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).

Olympus C-21 equivalent aperture:

Crop factor = 5.41
Aperture = f2.4

35-mm equivalent aperture = (f2.4) × 5.41 = f13

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