Tuesday, October 13, 2009
In the race for higher resolution, there are trade-offs with image quality. It all comes down to the limits of the image sensors and the individual photosites on those sensors.
Ever since the first digital cameras appeared, there has been a quest for more pixels. In large part, that’s because the more pixels an image contains, the finer detail it can present and the bigger we can blow it up before the pixels become visible to the eye. Today, we have compact digital cameras with nearly 15 megapixels, 35mm form-factor D-SLRs with 24-plus megapixels and medium-format D-SLRs with 60-plus megapixels.
Nikon Full-Frame Sensor
There’s also the term “photosite,” which generally refers to the light-capturing “pixels” on the image sensor. As long as we all know what we mean, we can use the terms “pixels” and “photosites” to mean both the light-sensitive photodiodes on an image sensor and the tiny squares that make up a digital image.
Medium-Format CCD Sensor
Photosites on image sensors come in a range of sizes, all quite tiny. In current D-SLRs, they range from 4.29 microns square in the 12.3-megapixel Four Thirds System cameras to 8.45 microns in Nikon’s 12.1-megapixel, “full-frame” D3 and D700. A micron is one-millionth of a meter; an average human hair is around 100 microns thick. Even the largest photosites are tiny.
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