As we have already found out, image quality depends on sensor size. The large sensor allows larger pixels as well, and they are capable of catching more light, which results in clearer and less noisy photos with color rendition.
But it is necessary to remember that sensor size doesn’t mean resolution and its measure units are not megapixels but inches or millimeters.
The majority of modern digital cameras have basically little, 1/3.2″ or 1/2.5″ sensors; some advanced compacts may possess larger, 1/1.8″ ones. At the same time, the number of megapixels increases from year to year although 6 megapixels or so would be enough to view photos on a computer screen or make average-size prints.
But only large sensor can justify the usage of so many megapixels. Bigger resolution, no doubt, means better detail and the possibility to print large photos but if sensor remains the same and the number of megapixels increases, the size of every single pixel suffers – they become smaller. On big resolution but little sensors pixels are so tiny that they can’t capture enough light and you receive noisy pictures.
Unfortunately, that is the way digital cameras’ manufacturers go: nowadays 12-megapixel compact cameras are quite standard, though sensors are as tiny as they used to be. Although compacts are equipped now with different noise reduction technologies, they can’t fully compensate for it as the increase in the quantity of pixels on the same sensor will lead actually to the decrease in image quality.
Average users night be confused by the numbers they give for sensor sizes: 1/3.2, 1/2.5 inches. What should be remembered here is that bigger numbers in the denominator mean smaller sensors. The table below shows the correspondence of those ambiguous inches to a sensor’s physical size.
| Sensor size, inch | Sensor Size, mm |
| 1/3.2” | 4.5×3.4 |
| 1/3” | 4.8×3.6 |
| 1/2.7” | 5.4×4 |
| 1/2.5” | 5.8×4.3 |
| 1/2” | 6.4×4.8 |
| 1/1.8” | 7.2×5.3 |
| 2/3” | 8.8×6.6 |
| 4/3” | 18×13,5 |
| “APC-S” | 22.7×15.1; 23.7×15.6 |
| 35mm film, Full Frames | 24×36 |
| Medium Format | 50.7×39 |
The biggest but one value for sensor size is 36 x 24 mm that is a frame size in 35-millimetre film. Such sensors have full frame DSLR cameras. APS-C DSLRs use 22.7 x 15.1 mm (1.6 crop factor) or 23.7 x 15.6 mm (1.5 crop factor) sensors.
The price tag of a camera largely depends on the sensor that it houses. That’s why compacts are affordable and aim at the middle-of-the-road audience, and full frames are expensive camera for professionals.
