A couple of things I don't understand with regards to the memory cards in my D7000. I have two SanDisk Extreme Pro 8GB cards installed.
The manual states that the approximate number of NEF (14-bit RAW) files that can be stored on an 8GB card is 223, with an average file size of 19.4MB.
Now, 223 x 19.4 = 4326.2MB, let's say 4.33GB. So my first question is, what happens with the remaining 3.67GB? My brain is telling me that an 8GB card should be able to store 400 x 20MB images.
My second question concerns the role played by the card in Slot 2;
If I set the option RAW Slot 1-JPEG Slot 2, the control panel does indeed display 223 images remaining with both cards empty.
If I choose Overflow for Slot 2, the number of remaining shots is reduced quite dramatically to 158. This is the part I am really struggling with. When set to Overflow, Card 2 is only used when Card 1 is full. So if Card 1 can hold 223 images, why can't Card 2 hold another 223 images? I fully expected to see 446 images remaining in the control panel? I know these are approximate numbers, but to drop down so much in Overflow mode just doesn't make any sense to me. I guess I'm looking at it purely from a 'space on a drive' viewpoint, but there must be more to it than that.
Can anybody shed any light on this (no pun intended), and put me out of my misery?