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-   -   8mp equals more like 3mp. Why? (https://forums.steves-digicams.com/general-discussion-11/8mp-equals-more-like-3mp-why-115898/)

leeraff Mar 3, 2007 5:45 AM

Pretty certain Im going to experience a "doh" moment here but a little confused.

My 8 megapixel camera generates picture files that are generally 2.9 to 3.2 mp. Why is that? What am I missing here why picture files aren't, in fact, 8 megapixels. Now, RAW picture files are generally much closer to 8mps.

Again, I fully expect a "boy don't I feel stupid" moment but I am racking my brain here.

NHL Mar 3, 2007 6:27 AM

The JPEG 'files' generated by the camera are compressed - i.e. redundant data are removed:
http://en.wikipedia.org/wiki/JPEG

stowaway7 Mar 3, 2007 7:28 AM

Are you sure you're not confusing MP (megapixils)& MB (megabytes)?

Bob Nichol Mar 3, 2007 4:25 PM

Most digital images use 24 bit colour which is 3 bytes per pixel. This comprises 8 bits or 1 byte per colour, red, green, and blue. an 8 megapixel (MP) image should be about 24 megabytes (MB) large however the jpeg process is able to compress out redundant data in the file to get down to 3-5MB size. See JPEG for details.

All digital cameras, except those using the Foveon sensor, use a colour filter array to generate the colour image. Each photo site only reports one colour and the other 2 colours are invented from adjacent photo sites. Since a RAW file is a direct dump of the sensor you will see about an 8-12MB file. A raw conversion application is required in your computer to process the image and invent the missing colours. See Color Filter Array for details.

leeraff Mar 3, 2007 10:10 PM

And the "doh..." Yes, megapixel versus megabyte. Makes much more sense.

Thanks for the replies.


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