Memory card issue

[futureal33]

Hi All,

Just wondering if anyone could offer me any fairly urgent suppport, as Im shooting a wedding tomorrow.

I have 2 5D3s and both have a 16GB Sandisk Extreme CF card in them.
Both cards are freshly formatted.

Both cameras recording Full RAW.

The first camera displays 533 pics remaining
The second camera displays 336 pics remaining

Swap the cards around the from one camera to the other, and the numbers dont swap?! Its like the second camera isn't seeing the full capacity of the card?

Any ideas?!
Thanks

 

[futureal33]

Fixed, but omg weirdest fix ever!!

I had the ISO on Auto on the second 5D3, and 100 on the first 5D3.

By changing from Auto ISO to 100, both cameras now show 533 pics remaining

 

[admirable]

It's not weird, high ISO takes up more space

 

[PitaDaVespa]

It's not weird, high ISO takes up more space

x2