Digital Camera resolution

The amount of detail that the camera can capture is called the resolution, and it is measured in pixels. The more pixels a camera has, the more detail it can capture and the larger pictures can be without becoming blurry or “grainy.”

Some typical resolutions include:
256×256 - Found on very cheap cameras, this resolution is so low that the picture quality is almost always unacceptable. This is 65,000 total pixels.
640×480 - This is the low end on most “real” cameras. This resolution is ideal for e-mailing pictures or posting pictures on a Web site.
1216×912 - This is a “megapixel” image size — 1,109,000 total pixels — good for printing pictures.
1600×1200 - With almost 2 million total pixels, this is “high resolution.” You can print a 4×5 inch print taken at this resolution with the same quality that you would get from a photo lab.
2240×1680 - Found on 4 megapixel cameras — the current standard — this allows even larger printed photos, with good quality for prints up to 16×20 inches.
4064×2704 - A top-of-the-line digital camera with 11.1 megapixels takes pictures at this resolution. At this setting, you can create 13.5×9 inch prints with no loss of picture quality.

Photo courtesy Morguefile
The size of an image taken at different resolutions
High-end consumer cameras can capture over 12 million pixels. Some professional cameras support over 16 million pixels, or 20 million pixels for large-format cameras. For comparison, Hewlett Packard estimates that the quality of 35mm film is about 20 million pixels [ref].

Next, we’ll look at how the camera adds color to these images.
How Many Pixels?
You may have noticed that the number of pixels and the maximum resolution don’t quite compute. For example, a 2.1-megapixel camera can produce images with a resolution of 1600×1200, or 1,920,000 pixels. But “2.1 megapixel” means there should be at least 2,100,000 pixels.

This isn’t an error from rounding off or binary mathematical trickery. There is a real discrepancy between these numbers because the CCD has to include circuitry for the ADC to measure the charge. This circuitry is dyed black so that it doesn’t absorb light and distort the image.