rjsphd Posted March 27, 2018 Share #1 Posted March 27, 2018 (edited) Advertisement (gone after registration) Pardon my ignorance, but I just put a fresh 32 GB SD Card (SanDisk Extreme Pro) into my M240 and am perplexed. First, my camera tells me I have 29.7 GB of usable space--what happened to 7% of my capacity off the bat? Second, it tells me I have 872 images to shoot, or roughly 34mb per shot. With a 24mb sensor, what is taking up the other 10? (I am shooting only DNG compressed.) Thanks in advance, Rob Edited March 27, 2018 by rjsphd Link to post Share on other sites More sharing options...
Advertisement Posted March 27, 2018 Posted March 27, 2018 Hi rjsphd, Take a look here SD card math. I'm sure you'll find what you were looking for!
pico Posted March 27, 2018 Share #2 Posted March 27, 2018 Pardon my ignorance, but I just put a fresh 32 GB SD Card (SanDisk Extreme Pro) into my M240 and am perplexed. First, my camera tells me I have 29.7 GB of usable space--what happened to 7% of my capacity off the bat? Second, it tells me I have 872 images to shoot, or roughly 34mb per shot. With a 24mb sensor, what is taking up the other 10? (I am shooting only DNG compressed.) To keep the explanation simple, the SD Card reserves space for its house-keeping, such as a table of bad blocks. That part of the card is not accessible by the user. We cannot see it. I won't check your math, but a GB in computer terms is different in International System Units. Not to worry. 1 Link to post Share on other sites More sharing options...
marchyman Posted March 27, 2018 Share #3 Posted March 27, 2018 The "missing" 2.3 GB is in file system overhead. It takes space to store file metadata and the tree used to equate a name to the actual spots on the card that hold the data. Your camera has a 23 MegaPixel sensor. Pixels are not bytes. Uncompressed an image will be about 42 MB. Compressed sizes vary a lot depending upon content but tend to be about 28 MB in size. The camera is guestimating larger. 1 Link to post Share on other sites More sharing options...
Jaskar Posted March 27, 2018 Share #4 Posted March 27, 2018 The difference in capacity is caused by different ways of counting bytes. SD Card manufacturers count in Gigabytes (GB) while Windows displays the capacity in Gibibytes (GiB). The former is based on the decimal system and the later based on the binary system. 1 GiB equals approximately 1.07 GB Link to post Share on other sites More sharing options...
rjsphd Posted March 27, 2018 Author Share #5 Posted March 27, 2018 The "missing" 2.3 GB is in file system overhead. It takes space to store file metadata and the tree used to equate a name to the actual spots on the card that hold the data. Your camera has a 23 MegaPixel sensor. Pixels are not bytes. Uncompressed an image will be about 42 MB. Compressed sizes vary a lot depending upon content but tend to be about 28 MB in size. The camera is guestimating larger. I was indeed ignorant, especially on the latter point. Many thanks. Link to post Share on other sites More sharing options...
pico Posted March 27, 2018 Share #6 Posted March 27, 2018 I was indeed ignorant, especially on the latter point. Many thanks. This stuff is not intuitive. Welcome! Link to post Share on other sites More sharing options...
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