Image sizes. If the camera settings stays the same and the image is stored as a set of pixel values, why does the image size change?

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On my smartphone, the largest image is around 8mb and the smallest in the same camera settings is around 2mb (images of different objects though). Why is there such a huge difference in image size?

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2 Answers

Anonymous 0 Comments

It has to do with the way image compression works. If you have an image with large uniform areas, like a blue cloudless sky, compression is going to be a lot more efficient than with an image with a lot of detail. Let’s just assume you have 200 blue pixels in a row as opposed to a mix of blue and white in a cloudy sky, the image compression format can basically say “200 times blue” instead of saying “blue, then white, then blue, then white again…” Generally speaking, less change in color across a row of pixels means better compression. That’s why some images can be reduced to a very small size and some need more space, because they need to store more specific information about the different parts of the image.

Anonymous 0 Comments

The images are likely being compressed.

Say for example you take a picture of someone in front of a flat white wall. Uncompressed the photo file would have to explicitly store that every single individual pixel of the wall is white, while a compressed file would store “all the pixels between *here* and *here* is white.

Uncompressed: 1, white 2, white 3, white 4, white…

Compressed 1 – 4, white.

Photos of highly varied and colorful scenes can’t be compressed as much and therefore the file is larger.