Help with NEF

niemeyjtniemeyjt Posts: 64Member
edited September 2015 in General Discussions
I am using 32Gb cards in my D7200 set one to NEF and two to JPEG. The "shots left" display shows 589 on a new card and I am trying to calculate why. Can someone help me with my sums / tell me where I have made a wrong assumption?

To start, the raw image will be 24MP - so 24,000,000 pixels

NEF encodes each pixel as 14 bits - so picture will be 336,000,000 bits

8 bits in a byte - so each picture will be 42,000,000 bytes

Using the salesman's Mb(1), each picture is thus 42Mb

32 Gb SD card = 32,000Mb - so should hold 32,000/42 = 762 photos. 25% more than 589.

So where have I gone wrong?

Looking at the NEF files on a PC I see they are between 29Mb and 33Mb - so less than 42 - so I would expect to fit even more on the SD Card.

Also, why are NEF files different sizes? Is there some optimisation taking place with them too?



(1) salesman's Mb = 1,000,000 bytes rather than 1,048,576 - used to make smaller disks seem bigger on the box label!


  • IronheartIronheart Posts: 3,017Moderator
    The counter is highly conservative, based on worst case with a head-wind. Files are lossless-ly compressed, so a picture with a lens cap on will be smaller than a field of daisies. You will be able to squeeze more files onto a card, YMMV.
  • heartyfisherheartyfisher Posts: 3,181Member
    The space on the card is not like a bucket of water, more like a bucket of bricks. so the volume of the content is never as much as the total volume of the bucket.
    Moments of Light - D610 D7K S5pro 70-200f4 18-200 150f2.8 12-24 18-70 35-70f2.8 : C&C very welcome!
    Being a photographer is a lot like being a Christian: Some people look at you funny but do not see the amazing beauty all around them - heartyfisher.

  • paulrpaulr Posts: 1,176Member
    Good analogy Heartyfisher
    Camera, Lens and Tripod and a few other Bits
Sign In or Register to comment.