QUOTE(g.johnson @ Sep 2 2008, 05:30 PM)
QUOTE(Peter Creasey @ Aug 23 2008, 12:04 PM)
QUOTE(mcj @ Aug 23 2008, 01:38 AM)
"less power per pixel"
M, Here are some similar comments...
QUOTE
"Too many megapixels can actually impair a camera's performance. For example, the typical sensor in a consumer camera is 0.5-0.7 inches. The more millions of pixels, the smaller each pixel must be-and the smaller the pixel, the less light-gathering efficiency it has, and the worse the camera performs in low-light or stop-action shots."
Given the same optical arrangements, the same amount of light will fall on a given square mm, say, of the sensor regardless whether there are 1000 or 10,000 pixels in that square mm. So assuming that the sensor doesn't have some sort of threshhold below which no light is registered*, it should always be possible to simulate the response of the lower density detector by adding adjacent pixels together.
*I would guess that in practice that's a fairly safe assumption.
I almost misread your post. Yes, that could be one method used to create lower resolution images and a form of what you've written has already been in common use since the first digital image sensors' inception, as you'll see below. I can see that it would be similar, in principle, to a reflecting solar array in which the array size is fixed, but a greater number of smaller mirrors are used in place of a smaller number of larger mirrors to accomplish the same task of gathering light.
So far, we have only discussed the theoretical light gathering capabilities based upon pixel size* and thus have had to confine the theory to black and white photography. However, since it
is the digital realm and the vast majority of photographs are taken in colour,
that is what camera image sensors are designed to capture – especially since the quotes were mainly regarding common consumer-grade digital cameras and we
are, after all, trying to judge
overall image quality.
*As you'll see in the articles linked below, pixel size is relative, since what we have been commonly referring to as pixels are actually
photo-sites within the sensors. Within each photo-site are a number of
sensor pixels, however, after image processing, they are combined ("demosaiced" [de-mosaic-ed]) into a single
image pixel.
To gain a better understanding (or to get even more confused) regarding some of the various technical issues involved with camera sensors, here are some links to broaden horizons:
http://www.popphoto.com/cameras/4276/foveo...o-the-test.htmlQUOTE
Traditional CCD and CMOS sensors use a single layer of pixels that are set in a grid, relying on a pattern of microscopic red, green, and blue filters to separate the components of light on each pixel. Interpolation and postprocessing merge the data into the color image we see on screen.
The most widely used sensor grid is the Kodak-developed Bayer pattern, with two green pixels for each red and each blue pixel. This aims to take advantage of the human eye's higher sensitivity to detail in green objects. For improved black-and-white detail, to which the eye is even more sensitive, luminance information from all pixels is combined.
http://en.wikipedia.org/wiki/Foveon_X3_sensorQUOTE
The Foveon X3 sensor is a CMOS[1] image sensor for digital cameras, designed by Foveon, Inc. and manufactured by National Semiconductor[2] and Dongbu Electronics.[3] It uses an array of photosites, each of which consists of three vertically stacked photodiodes, that are organized in a two-dimensional grid. Each of the three stacked photodiodes responds to different wavelengths of light, i.e., each has a different spectral sensitivity curve. This is due to that fact that different wavelengths of light penetrate silicon to different depths.[4] The signals from the three photodiodes are then processed, resulting in data that provides the three additive primary colors, red, green, and blue.
The Bayer filterQUOTE
A Bayer filter mosaic is a color filter array (CFA) for arranging RGB color filters on a square grid of photosensors. Its particular arrangement of color filters is used in most single-chip digital image sensors used in digital cameras, camcorders, and scanners to create a color image. The filter pattern is 50% green, 25% red and 25% blue, hence is also called GRGB[1] or other permutation such as RGGB.[2]
DemosaicingQUOTE
A demosaicing algorithm is a digital image process used to interpolate a complete image from the partial raw data received from the color-filtered image sensor (via a color filter array or CFA) internal to many digital cameras in form of a matrix of colored pixels. Also known as CFA interpolation or color reconstruction, another common spelling is demosaicking.
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