Time to clarify. "Megapixels" these days is often used to refer to the number of CCD/CMOS elements; now, as we all know, it takes three numbers/sensors to form one RGB pixel. However, most digital cameras do NOT have three sensors per pixel; rather, they sprinkle the colors in a rather logical pattern (a Bayer array, IIRC) and interpolate. For example, about 1/2 of the sensors in most CCDs are green sensors, 'cause our eyes are most sensitive to luminosity differences in the green channel of positive light images. Red is next-most frequent and blue least. You can see this by looking at the various channels of a fairly long exposure; without fail, the green channel will have the most detail (and least noise) and the blue will have the least detail and be most noisy. (In effect, you're only getting something like 1/6-1/8 of the total number of pixels for the blue channel. The camera's processor places them on an appropriate grid and interpolates for each channel separately, combining them for image output.) The "megapixel" number you see tends to be the actual sensor count, and thus is not necessarily correlating with any number of pixels for output. Fuji is one exception to all of the above; they use their own wacky rotated honeycomb sensor array and interpolate the whole mess to make whoppingly big images, rather than the quasi-standard Bayer array. Some company-or-other has managed to layer their CCD layers atop one another; their sensors have true RGB for every single pixel. They're also hellishly expensive and have not yet hit the market. Also, the hyper-expensive scanning digicams ($20,000+) usually sample true RGB. </digishutterbug> > -----Original Message----- > From: tclug-list-admin at mn-linux.org > [mailto:tclug-list-admin at mn-linux.org]On Behalf Of Chuck Cole > Sent: Wednesday, September 04, 2002 10:28 PM > To: tclug-list at mn-linux.org > Subject: RE: [TCLUG] Digital cameras > > > You're learning the new math.. How many are white? ie, does the white > light optical resolution match that? Same for .. say pure red > (ie, no light > through the other two colored filters.. or cyan, etc)? > > > > > -----Original Message----- > > From: tclug-list-admin at mn-linux.org > > [mailto:tclug-list-admin at mn-linux.org]On Behalf Of Tim Wilson > > > > > > On Wed, Sep 04, 2002 at 07:45:32PM -0500, Chuck Cole wrote: > > > "Megapixel" alone doesn't tell you whether it's a linear or > > rectangular > > > array. Sometimes the details really matter and pixel-level > > asymmetry can > > > really mess up image processing math. Many CCD devices are > > TV format > > > (something unrelated to 640x480 maybe 512x320. interlaced > > formats can get > > > into the act also), scientific ones have square pixels and usually a > > > symmetric array like 512x512 or larger. Cameras are > > usually not meant (ie, > > > "not supported") for any technical or scientific purpose, > > so it may be best > > > to ignore the details finer than +/- 25% pixel count unless > > you have a real > > > need to know. Kodak supports some of their cameras.. > > including some source > > > code. > > > > Well for the record, my Canon S40 manual says 4.1 million total pixels > > and 4 million effective pixels. The largest image the camera produces > > is 2272x1704 which works out to be: > > > > >>> 2272*1704 > > 3871488 > > > > How's that for an answer. :-) > > > > -Tim > > > > -- > > > > > _______________________________________________ > Twin Cities Linux Users Group Mailing List - Minneapolis/St. > Paul, Minnesota > http://www.mn-linux.org > tclug-list at mn-linux.org > https://mailman.mn-linux.org/mailman/listinfo/tclug-list