How Your Camera Makes a JPEG Image

When you shoot with your camera in JPEG mode (or in TIFF mode, if the camera provides such a feature), a lot of things happen after the sensor makes its capture. First, the image data is amplified. The signals generated by your camera’s image sensor are actually quite weak, so they need to be boosted to a level that’s easier to work with. (When you increase the ISO setting on your camera, you’re doing nothing more than increasing the amount of amplification that is applied to the original data.) Unfortunately, just as turning up the volume on your stereo produces more noise and hiss along with the music, turning up the amount of amplification in your camera increases the amount of noise—ugly speckly patterns ...

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