: Why JPEG files saved in my digital camera are higher size vs JPEG files saved in my computer? When I took pictures using my digicam, it saves those on higher size (over 1 MB) JPEG files.

@Vandalay110

The answer is obviously compression.

An typical camera image is 3 long strings of numbers (between 0 and 255), one string for Red, one string for Green, and one string for Blue. The number is the brightness value for an individual pixel. The length of each string is the pixel width of the image mulitplied by the pixel height of the image. A byte is a unit of storage which is capable of storing a number between 0 and 255. So the size of an RGB image is approximately Width x Height x 3 bytes in size.

To store this, one can merely transcribe this (by hand on paper, computer file, etc).

In practice, there are long runs of the same number in each string. So instead of transcribing a long sequence of one hundred 2s (100 bytes), you can write down a single byte as a flag, the number 100, and the number 2 (3 bytes). This is very basic compression. The "flag" is needed for when you want to take the file from storage and re-render the image.

JPEG is a more complicated form of compression. The example I gave above is a lossless form of compression because the transcription process preserves the original pixel numbers. JPEG can give you (generally) much smaller files because it THROWS AWAY pixel numbers. So at higher quality settings, the transcribed file size is larger but the image quality is better. To get a smaller file size (with the same size rendered image), JPEG degrades quality.

For a camera, there is a tug of war between picture quality and the cost of embedding file storage in the device. So the manufacturer wants to have a default setting which allows their marketing team to say "Stores 6 Gabillion images!*" without reviewers saying "Image quality sucks. DO NOT BUY". For the marketing (and Just Want it to Work consumers), JPEG compression is a requirement. For the reviewers, a high quality, low compression, higher file size setting as default is a requirement.

Note that for anything to be rendered on a screen, printer or other device, it is no longer JPEG. Compression and file type, GENERALLY speaking, only exists when it is stored unopened and unviewed. This is often confusing to people, partly because the same units of measurement are used for memory size and mass storage capacity.

TLDNR; your file sizes are larger coming off the camera because when you open them, you are resaving them with a lower quality, higher compression.

When I do camera work for business (still-shot, commercial style photography), I shoot them in Camera RAW format, which is the best possible quality from the camera because it is nearly identical to what the sensors in the camera report (ignoring any engineering {magic and funny business}). The file sizes are larger.

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@Holmes874

Various possible reasons:


you are re-saving the images at a lower resolution. fewer pixels = less data = smaller file size
your camera is likely saving JPGs with minimal compression. Your desktop software is using a higher level of JPG compression.
Even if your software is using the SAME compression as your camera, each time you re-save a JPG, you lose data due to the lossy compression. So it will still be smaller.
your desktop software is stripping out a lot of meta data that the camera attaches to the image.
your camera is perhaps NOT saving as JPG, but in RAW format, which is a lot larger than a JPG file.

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