Over the years we have compiled the following table of common sensor sizes for digital cameras, camcorders and cameraphones. We hope this helps readers to make sense of the pervading irrational measurement system.
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Unravelling Sensor Sizes
Over the years we have compiled the following table of common sensor sizes for digital cameras, camcorders and cameraphones. We hope this helps readers to make sense of the pervading irrational measurement system.
Sensor Size vs Resolution There is a direct relationship between the number of photosites on an image sensor and the number of megapixels it resolves because each photosite collects the equivalent of one pixel of photons (units of light). At the same time, all sensors are affected by the background electronic noise that degrades the signal in all electronic devices. This noise is directly related to the size of the image sensor and the number of photosites it contains. Consequently, two factors come into play when considering how much a digital image will be degraded by electronic noise: the size of the sensor and the number of photosites it contains. The larger the area of the sensor with respect to its photosite count, the larger will be each photosite and the lower the affect of electronic noise on the digital image signal. Large photosites can also collect more photons, thereby providing a wider dynamic range in digital images. (Dynamic range is the range of tones from black to white.) Although camera manufacturers may introduce post-capture noise-reduction processing, you cannot escape basic physics: the larger each photosite’s area, the more photons it can collect, the stronger the digital signal and the greater the dynamic range and tonal clarity in the final print. To take a couple of examples: Assuming a compact 12-megapixel digicam with a “1/1.7-inch” type sensor that records high-resolution images at 4000 x 3000 pixels. This sensor’s imaging area is only 7.6 x 5.7 mm in area, which means each photosite is just 1.9 microns square in area (7.6 mm øƒ · 4000 pixels). Compare it with a 12.2-megapixel DSLR that has a sensor measuring 22.2 x 14.8 mm, which captures images at 4272 x 2842 pixels. Using the same calculation, we have a photosite area of 22.2 øƒ · 4272 pixels = 5.2 microns square. Even better is a ‘full frame’ DSLR with a sensor measuring 36 x 24mm, which records images at 4368 x 2912 pixels and has a photosite area of 8.24 microns square. Which camera will provide the greatest dynamic range – and the best overall picture quality? (The third one, of course.)
How Many Megapixels Do You Need?
Output size – how large you will print images – it the most critical factor dictating your resolution requirements. At an ideal printing resolution of 300 dots/inch, the resolution requirements for different print sizes are as follows: 7 x 5 inch size – 2100 x 1500 pixels (equivalent to 3.2 megapixels) 8 x 6 inches – 2400 x 1800 pixels (equivalent to 4.4 megapixels) 10 x 8 inches – 3000 x 2400 pixels (equivalent to 7.2 megapixels) 16.5 x 11.7 inches(A3) – 4950 x 3510 pixels (equivalent to 17.4 megapixels) 19 x 13 inches (A3+) – 5700 x 3900 pixels (equivalent to 22.3 megapixels) As you can see, you only need 10 megapixels if you plan to print your pictures larger than A4 size.
But that’s not the entire story; because we view A3 and A3+ enlargements from greater distance, the resolution requirements drops to around 200 dots/inch. This, in turn, brings our camera resolution requirements down as follows: 19 x 13 inches (A3+) – 3800 x 2600 pixels (equivalent to 9.9 megapixels) In other words: you can produce excellent A3+ prints from a 10-megapixel camera – provided you start with high-quality images. |
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