A few words MegaPixels & Image sensor size
A 1 MegaPixel image sensor to start with.
To double the resolution of this sensor (the sharpness/amount of details), the amount of pixels both length and width must be times two. So: (1*2) * (1*2) = 4 MegaPixels
To double the resolution, the amount of MegaPixels must be times 4
To double the resolution of a 4 MegaPixels sensor, you'll need 4*4 = 16 MP
To double the resolution of a 16 MegaPixels sensor, you'll need 16*4 = 64 MP
To double the resolution of a 64 MegaPixels sensor, you'll need 64*4 = 256 MP
So, it's not a major resolution increase when having a 6 MP camera, and now buying a 8 MP camera, you'll hardly notice.
To be as sharp as 35 mm film can be, you'll need a ± 25 MP camera.
But what is more important than the amount of MegaPixels is the quality of the pixels. I had a digital compact camera of 6 MP, but the quality of the pixels was such crap; I had to reduce the length and width of the images by 50% to get decent pixel quality, which really left me with a 6/4 = 1.5 MP camera!
An image sensor is like a giant plane of millions of separate solar cells, each cell being sensitive for either Red Green or Blue. The lens projects an image on the image sensor, and each light sensitive cell produces an analog signal that is then calculated into a digital value.
Problem is that these cells are so small and the exposure is short, this causes rough inaccurate measurements that result in noise, especially in the dark areas.
Another problem with very small cells, is the lens's faults show large.
The solution for both problems is: a bigger image sensor.
A typical size in a 6 MP digital compact camera is: 1/2.5 which is only 7.182 * 5.760 mm, while a digital SLR 6 MP camera's sensor can be 23.7 x 15.5 mm (8.88 times larger surface!).
If the image sensor would be twice as large (length and width), and still 6 MP, then each light sensitive cell would get 4 times more light, and less of the lens's faults will show.
This great improvement of image quality will of course be a bit more expensive and make the camera a bit larger. That and not using the RAW file format is why most digital compact cameras produce such incredible low quality.
Good verses Bad pixels:
 
One MegaPixel = 1.000.000 pixels
Because a 1 MP camera produces 1.000.000 RGB pixels, one would expect there to be:
1.000.000 Red sensors
1.000.000 Green sensors
1.000.000 Blue sensors
But in reality, there are only:
250.000 Red sensors
500.000 Green sensors
250.000 Blue sensors
The missing 2.000.000 sensors are simply predicted in between, thus guessed really. A digital camera that (has to) use a "Bayer filter arrangement" on the image sensor (which most do) are build like this:
The Bayer arrangement of color filters on the pixel array of an image sensor.
To get high quality pixels, the cells/sensors must be large, 1.000.000 Bayer pixels should produce only 250.000 RGB pixels, and of course using lossless compressed RAW (with 4096 tones per channel) instead of lossy JPG (only 256 tones per channel) will give a much higher image quality, especially because more of the dynamic range can be captured.
|
LaesieWorks
Movie Compression
