File Size
The storage a file occupies, determined by pixel count, bit depth, channel count and compression.
Formula / rule
Bytes ≈ px × channels × bits / 8
Measured in
MB
In depth
An uncompressed 16-bit RGB file needs six bytes per pixel, so a 45-megapixel image occupies about 270 MB before any compression. Raw files vary with scene content because their lossless compression depends on redundancy, which is why a foggy frame is smaller than a detailed one from the same camera.
Examples in practice
Two frames from the same camera can differ by 30 per cent in size purely because one contains more fine detail.