# ISO vs. Megapixels, how to convert? **URL:** \ **Category:** Factual Questions\ **Created:** [October 18, 2013, 6:25am UTC](https://boards.straightdope.com/t/iso-vs-megapixels-how-to-convert/671558 "2013-10-18T06:25:53Z")\ **Posts on this page:** 1\ **Page:** 3
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [October 20, 2013, 1:15pm UTC](https://boards.straightdope.com/t/iso-vs-megapixels-how-to-convert/671558/41 "2013-10-20T13:15:25Z")
> [@MichaelEmouse](#): > > Weird, my Canon 300 ELPH is not by any stretch a high end compact camera (I got it for about 200$ more than a year ago) and it says it has 12.1MG and when I look at the number of pixels in a picture, it actually has about 4000 by 3000 pixels. Is it fooling me in some way or does the marketing trick kellner describes not apply to it? The image sensor in your camera only has 12 million pixels total (R + G + B). That’s only 4 million fully resolved pixels. The image processor in your camera interpolates this information and produce an image file with 12-million pixels, but it can never have a full 12-million pixels’ worth of resolution. This isn’t just a marketing gimmick though. In reality the 12-megapixel sensor actually has 6 million green pixels, and 3 million each of red & green pixels. Green is in the middle of the visible spectrum, so that’s where the camera (and our eyes too) get most of the contrast. You can think of green pixels producing an outline of a shape, and red/blue pixels adding color to that shape. And also, because of the way these green pixels are arranged ([Bayer filter pattern](http://en.wikipedia.org/wiki/Bayer_filter)), if you save it as a 6-megapixel image file, you actually lose a bit of information. To preserve the full resolution, you want to save it as a 12-megapixel image. [Previous page](https://boards.straightdope.com/t/iso-vs-megapixels-how-to-convert/671558.md?page=2)