Why aren't uncompressed RAW files larger?

[Jonathan Kingston]

Just bought an X-T30 and am new to the wonderful world or shooting RAW. I have (what is I suspect) a naive question. Why aren't uncompressed RAW files larger than we see them?

My logic is this:
  X-T30 shoots in 14 bits per channel.  3 colour channels. So 42 bits (or 5 1/4 bytes) per pixel.
  Images are 6,240 pixels wide, 4,160 pixels high. 25,948,400 pixels total.
  So I'd expect an uncompressed RAW file to be about 25,948,400 * 5 1/4 bytes big. Or about 130MB.
  But the uncompressed .RAF files come out around 56MB 
Which bit of my assumptions or logic have I got wrong?

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[jlmphotos]

50mb is about correct. My X-T2 generates 50mb as does my X-H1.  So if you are hitting 56mb uncompressed that's about right.

[Jonathan Kingston]

Well yes. That's what everyone reports. But the mathematics would suggest that uncompressed raw files should be 2x - 3x bigger at about 130MB. I'm just curious as to why they're not. 

[jerryy]

You are thinking the data is stored as RGB triples, but the camera manufacturers use various ways to pack the sensor data which has the side benefit of compressing the stored files.

Try this: use your favorite raw conversion program to convert one of your raw files and export it as a TIFF file (uncompressed, 16 bit, full quality, etc., etc., etc.) and you will get around 156 MB or so.

Edited April 16, 2019 by jerryy

[Doug Pardee]

On 4/6/2019 at 3:40 AM, Jonathan Kingston said:

My logic is this:
  X-T30 shoots in 14 bits per channel.  3 colour channels. So 42 bits (or 5 1/4 bytes) per pixel.

Each pixel is a single color channel. There are red pixels, green pixels, and blue pixels.

Edited April 27, 2019 by Doug Pardee