A trivial question about number of pixels
The Nikon website, in listing the specifications of the Nikon D800, says that it has 36.3 million effective pixels and 36.8 million total pixels.
It also says the image area is 7360 X 4912 which comes to 36,152,320 pixels or about 36.2 million pixels.
Can anyone explain the discrepancy? Perhaps there are extra pixels which contribute to the image but are not actually in the image area?
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#1. "RE: A trivial question about number of pixels" | In response to Reply # 0pdekman Nikonian since 17th Nov 2005Fri 18-Oct-13 03:20 PM
Total vs. effective pixels is typically different in that edge pixels are available to accomodate the demosaic algorithms but are not part of the image pixel count. As to the difference between 36.3M effective and 36.15 image pixels? Perhaps some small difference in the die structure vs. an exact 3:2 image size and some of the effective pixels were cropped off. I'm just guessing on this one.
#2. "RE: A trivial question about number of pixels" | In response to Reply # 0ericbowles Nikonian since 25th Nov 2005Fri 18-Oct-13 05:48 PM
Paul's explanation makes sense. The difference works out to about 25 extra pixels on each side or about 0.1 mm on a 35mm sensor.
It's interesting - the Nikon 1 sensor on the V2 has a much larger "unused" area.
And for what it's worth, if you took the pixel size on the existing V1/V2 and applied it to an FX size sensor, you get a 75 megapixel sensor. D4X anyone?
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#3. "RE: A trivial question about number of pixels" | In response to Reply # 2slothead Nikonian since 11th Aug 2009Fri 18-Oct-13 09:54 PM
Good answers guys. And Leonard, I don't think that is a trivial question at all. I've been wondering about the pixel counts for years - but never asked.
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#4. "RE: A trivial question about number of pixels" | In response to Reply # 0
In addition to the, already mentioned, extra active pixels around the edges of the sensor that provide additional data for interpolation of RGB values near the image border during de-mosaicing, there are also a number of masked pixels, also sometimes referred to as optical black. These masked pixels do not capture any photons, but are read and their output A/D converted. Their average determines the offset (essentially the noise floor) subtracted from other pixel data to shift the black point to zero in the raw data (at least on Nikon cameras).