Epson PhotoPC 850 Zoom vs. HP Photosmart C912

Comparison

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Epson PhotoPC 850 Zoom

HP Photosmart C912

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Megapixels

1.90

2.20

Max. image resolution

1600 x 1200

Sensor

Sensor type

CCD

Sensor size

1/2" (~ 6.4 x 4.8 mm)

2/3" (~ 8.8 x 6.6 mm)

Sensor resolution

1589 x 1195

1710 x 1286

Diagonal

8.00 mm

11.00 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	:	1.89
(ratio)

Epson PhotoPC 850 Zoom		HP Photosmart C912

Surface area:

30.72 mm²

58.08 mm²

Difference: 27.36 mm² (89%)

C912 sensor is approx. 1.89x bigger than 850 Zoom sensor.

Pixel pitch

4.03 µm

5.15 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: 1.12 µm (28%)

Pixel pitch of C912 is approx. 28% higher than pixel pitch of 850 Zoom.

Pixel area

16.24 µm²

26.52 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:

Pixel area difference: 10.28 µm² (63%)

A pixel on HP C912 sensor is approx. 63% bigger than a pixel on Epson 850 Zoom.

Pixel density

6.16 MP/cm²

3.78 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: 2.38 µm (63%)

Epson 850 Zoom has approx. 63% higher pixel density than HP C912.

To learn about the accuracy of these numbers, click here.

Specs

Epson 850 Zoom

HP C912

Crop factor

5.41

3.93

Total megapixels

Effective megapixels

Optical zoom

3.2x

Digital zoom

Yes

ISO sensitivity

100, 200, 400

25, 50, 100, 200, 400

RAW

Manual focus

Normal focus range

50 cm

Macro focus range

5 cm

10 cm

Focal length (35mm equiv.)

35 - 105 mm

34 - 108 mm

Aperture priority

Yes

Max. aperture

f2.0 - f2.8

f2.5 - f3.9

Max. aperture (35mm equiv.)

f10.8 - f15.1

f9.8 - f15.3

Metering

Multi, Center-weighted, Spot

Centre weighted, Spot

Exposure compensation

±2 EV (in 1/2 EV steps)

±3 EV (in 1/2 EV steps)

Shutter priority

Yes

Min. shutter speed

8 sec

4 sec

Max. shutter speed

1/750 sec

1/1000 sec

Built-in flash

External flash

Viewfinder

Optical (tunnel)

White balance presets

Screen size

Screen resolution

72,000 dots

127,000 dots

Video capture

Max. video resolution

Storage types

Compact Flash (Type I or II)

CompactFlash type I

USB

USB 1.0

HDMI

Wireless

GPS

Battery

AA NiMH (4) batteries (supplied)

AA (4) batteries (NiMH recommended)

Weight

360 g

630 g

Dimensions

107 x 88 x 65 mm

144 x 91 x 105 mm

Year

1999

2000

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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

Epson 850 Zoom diagonal

The diagonal of 850 Zoom sensor is not 1/2 or 0.5" (12.7 mm) as you might expect, but approximately two thirds of that value - 8 mm. If you want to know why, see sensor sizes.

w = 6.40 mm
h = 4.80 mm

Diagonal = √

6.40² + 4.80²

= 8.00 mm

HP C912 diagonal

The diagonal of C912 sensor is not 2/3 or 0.67" (16.9 mm) as you might expect, but approximately two thirds of that value - 11 mm. If you want to know why, see sensor sizes.

w = 8.80 mm
h = 6.60 mm

Diagonal = √

8.80² + 6.60²

= 11.00 mm

Surface area

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

850 Zoom sensor area

Width = 6.40 mm
Height = 4.80 mm

Surface area = 6.40 × 4.80 = 30.72 mm²

C912 sensor area

Width = 8.80 mm
Height = 6.60 mm

Surface area = 8.80 × 6.60 = 58.08 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

850 Zoom pixel pitch

Sensor width = 6.40 mm
Sensor resolution width = 1589 pixels

Pixel pitch =	6.40	× 1000	= 4.03 µm
	1589

C912 pixel pitch

Sensor width = 8.80 mm
Sensor resolution width = 1710 pixels

Pixel pitch =	8.80	× 1000	= 5.15 µm
	1710

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

850 Zoom pixel area

Pixel pitch = 4.03 µm

Pixel area = 4.03² = 16.24 µm²

C912 pixel area

Pixel pitch = 5.15 µm

Pixel area = 5.15² = 26.52 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

850 Zoom pixel density

Sensor resolution width = 1589 pixels
Sensor width = 0.64 cm

Pixel density = (1589 / 0.64)² / 1000000 = 6.16 MP/cm²

C912 pixel density

Sensor resolution width = 1710 pixels
Sensor width = 0.88 cm

Pixel density = (1710 / 0.88)² / 1000000 = 3.78 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

850 Zoom 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
	1.33

Resolution horizontal: X × r = 1195 × 1.33 = 1589
Resolution vertical: X = 1195

Sensor resolution = 1589 x 1195

C912 sensor resolution

Sensor width = 8.80 mm
Sensor height = 6.60 mm
Effective megapixels = 2.20

r = 8.80/6.60 = 1.33

X = √	2.20 × 1000000	= 1286
	1.33

Resolution horizontal: X × r = 1286 × 1.33 = 1710
Resolution vertical: X = 1286

Sensor resolution = 1710 x 1286

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

850 Zoom crop factor

Sensor diagonal in mm = 8.00 mm

Crop factor =	43.27	= 5.41
	8.00

C912 crop factor

Sensor diagonal in mm = 11.00 mm

Crop factor =	43.27	= 3.93
	11.00

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).

850 Zoom equivalent aperture

Crop factor = 5.41
Aperture = f2.0 - f2.8

35-mm equivalent aperture = (f2.0 - f2.8) × 5.41 = f10.8 - f15.1

C912 equivalent aperture

Crop factor = 3.93
Aperture = f2.5 - f3.9

35-mm equivalent aperture = (f2.5 - f3.9) × 3.93 = f9.8 - f15.3

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