16GB CF card only shows 14.9GB capacity?

I've got a 16GB Compact Flash card. I formatted it in both Windows Explorer and also in-camera (EOS 7D) and when I choose to re-format again in-camera, it shows 14.9 GB capacity.

What's up with the extra GB?

HAAAA, the famous missing bits.

I will guess most of the bits gone is due to the following.

On your card, 16GB mean 16,000,000 bits, and what the system or the camera is showing you is 14.9 x 1024 Kilobytes (1 Kilobyte being 1024 bits hence x again 1024).

14.9 x 1024 x 1024 = 15623782.4, the rest is used to build what the system requires on the card to be used, for instance the FAT.

Bernard

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I measure my success in life not by my awards, but by the amount of smiles, hugs and kisses I get from my family on a daily basis !

Sethboy said:

I've got a 16GB Compact Flash card. I formatted it in both Windows Explorer and also in-camera (EOS 7D) and when I choose to re-format again in-camera, it shows 14.9 GB capacity.

What's up with the extra GB?

Click to expand...

Actually, this story has been going on for now over 20 years. When they sell hard drives and now memory cards (RAM is different) they sell by the thousands. So a 16 gig cf card has 16,000,000,000 bytes. But the computers calculate a 1Kilo byte as 1024 bytes. So your card is 15.6Gb only, then there is the directory, the 2 allocation tables...

In the mid-90s, there was a lawsuit against the big hard drive manufacturers that they lost (kind of), but they've somehow managed in keeping doing the same thing (it actually says so in the fine print). That's why a 2Tb hard drive is only 1.8Tb.

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Thanks
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The Business of Being a Photographer -- Lightroom Q&A

RAW capacity is not the same as STRUCTURED capacity.
Different ways of structuring the RAW capacity result in different USABLE space.

Similarly, different image content results in different image file sizes when shooting JPG.

If engineers knew EXACTLY how large each and every one of your images would be, the exact full capacity could be available for image storage...however, that is unreasonable.
(I just checked Canon 7d RAW files I shot today...even their sizes vary)

Solid state storage devices may have additional capacity YOU CANNOT SEE, reserved for "bad block revectoring"... on some devices this may be 80% additional capacity.

So... in real life, the RAW capacity allocated for "user stuff...like images" as a collection of fixed size "chunks/blocks" of storage... used to be 512 bytes per block, now 8192 is a common size. When you need storage (for an image), it receives as many "blocks" as necessary, probably not fully using all the space of the last block. Since all files/images are not uniform size, something has to keep track of which blocks belong to each file. This recordkeeping overhead is space that the "structure" must use to make the remaining space USABLE for you.

Be happy... 16Gb cards weren't possible just a few years ago... but are today.
I have cards from 64Mb... to 16Gb)

Just remember - every mem card will fail... they have limited write cycles...and lots of engineering to maximize their longevity... write wear leveling, write cycle monitoring, bad block revectoring, and more

Thanks everyone for valuable info.