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?

  • When set to overflow do you still have Raw+JPEG selected or Raw only?
    – Michael C
    Nov 29 '16 at 1:47
  • Yes, I've just realised (after reading Thomas's reply) that I still had the Image Quality set to RAW +Jpeg. Setting it to RAW only brings the number of remaining images back up to 223. Still a lot of dead space on that 8GB card though! Cheers! Nov 29 '16 at 12:23
  • The camera prefers to under-estimate rather than over-estimate the number of photos that can fit in the remaining space. This seems like a lot of under-estimation in this case, but it is still within a factor of 2 of what it should be. Remember that file sizes are given using 1024*1024 byte Megabytes but drive capacity is quoted in 1000*1000 byte megabytes as well, and that it is probably factoring in a small amount of free space left at the end (fragmentation would reduce performance).

  • In overflow mode the displayed number of remaining photos is shown only for the current card, not both cards.

  • I'm guessing that when you set to overflow mode, it went back to putting your backup JPEG on the first slot along with the RAW, so you are storing both a RAW and JPEG on the first slot, reducing the number of images.

  • Thanks Thomas, I was kind of aware of the 1024 byte MB etc, but it still seems a lot of 'dead' space on the card. But you and Michael are both right - I still had the Image Quality set to RAW +Jpeg, so your third point makes perfect sense. I'm still unclear as to what happens when card 1 fills up in Overflow mode - can I then shoot another 223 (approx) images on card 2, does the counter reset once card 2 comes into action? Nov 29 '16 at 12:33
  • My theory is that you are correct. When it moves on to card 2, it will then show you the remaining shots on card 2. But I am not 100% certain without having the manual or the camera in front of me. Nov 29 '16 at 22:59
  • Well I guess there's only one way to find out - I'll have to fill up card one and see what happens... BTW, are these 'pop up' website tips for real..? "But avoid … Asking for help, clarification, or responding to other answers" I thought this was the whole purpose of a website such as this? Am I missing something here? Dec 4 '16 at 20:40
  • Comments and answers are separate things. The tip about avoiding asking for help or responding to other answers is because that's not what answers are for. You need to use comments for that instead. Dec 4 '16 at 23:50

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