Advertised vs. formatted CF card capacity?

[fwhitesides]

I am curious as to what everyone else is getting from their 512mb (or other value) card. Are you getting a straight advertised capacity or a lesser value due to formatting and such? What's the average space loss due to file system formating?

THnaks.

[karusel]

It's simple. 512 MB in this case ain't actually 512 megabytes it's something they now call MiB (mibibytes) and 512 MiB is - 512.000.000 bytes. So, 512.000.000/1024/1024=488,28 MB. The factories just don't seem to like the idea that 1 KB = 1024 B :roll:

[PeterS45]

As you will probably know a 512 Mb card isn't really 512 Mb :shock: .

It's about 512.000.000 bytes and when you divide that by 1024 (twice: the first time to calculate bytes into Kb and the second time to get Kb into Mb) it will result in 488,28 Mb :evil: and therefore 256 Mb in fact is 244,14.........

My SanDisk 256 Mb card in fact is 255.541.248 bytes and that results in 243,70 Mb, but my DaneElec is 255.827.968 and that's 243,98 Mb. Formatting only takes 8.192 bytes (8 Kb).

[vvizard]

And just to add some confusion, it's never this simple either. The filesystem itself will always take up a certain % of the formatted space. And just how much, depends on the filesystem in use. Cameras usually use FAT16 or FAT32, so there's not a big issue, but computers use a whole lot of different filesystems, so there it might differ quite a lot how much capacity is "lost" due to the filesystem. But there we're talking 200GB harddrives, so it's not a problem to most people. I'll rather have a lightning fast journaling FS that wastes 2% of my capacity, than having a slow non-journaling, boot-fschking FS that uses 1%.. Just my .02

[Cadwell]

Ahh.... the old "decimal megabyte fiddle". This is the same con that has been perpetrated on the computing consumer for many years. I'm old enough to remember when a megabyte was 1,048,576 bytes and not 1,000,000 bytes as they'd like us to believe nowadays. (but then I also remember paying £25,000 for a 1 Gigabyte hard disc :cry: )

What this con means is that you get @48K less per MB than you thought you were getting. On a supposedly 512MB card, you lose @ 24MB or about 4.5%.

Then of course, there are some small loses due to the file system.

[Vegas Poboy]

Hhere is another factor to consider ISO speed settings will affect the number of shots held by the card . The higher the ISO the less capacity of the # of shots on the card. So you may want to factor that in when buying for capacity.

[fwhitesides]

Hhere is another factor to consider ISO speed settings will affect the number of shots held by the card . The higher the ISO the less capacity of the # of shots on the card.

Interesting. Can you explain why the ISO speed has an effect on the file size?

[Vegas Poboy]

Hhere is another factor to consider ISO speed settings will affect the number of shots held by the card . The higher the ISO the less capacity of the # of shots on the card.

Interesting. Can you explain why the ISO speed has an effect on the file size?

Not really I just think the higher the ISO the larger the file but this only me guessing. I mark all of my cards with the count # for Jpeg & RAW files with the Camera set @ 400 ISO. Just for a quick reference.

[Dans_D60]

Hhere is another factor to consider ISO speed settings will affect the number of shots held by the card . The higher the ISO the less capacity of the # of shots on the card.

Interesting. Can you explain why the ISO speed has an effect on the file size?

Not really I just think the higher the ISO the larger the file but this only me guessing. I mark all of my cards with the count # for Jpeg & RAW files with the Camera set @ 400 ISO. Just for a quick reference.


Storage capacity:

Formatting CF cards even if all are FAT16 may indeed result in different sizes. This has to do with cluster sizes and all kinds of other factors. The files stored on your CF card need addresses and other information so the camera or computer can find them. That simply takes some of the storage space and depending on the capacity of the CF card and where it was formatted will result in some data being used. This is NOT lost data. It is necessary for the CF card to work. It’s no different than your disk storage devices.

As far as ISO. Yes different ISO settings can alter the final image size. All files on your CF card (at least from Canon cameras) are compressed. Even the RAW files are compressed somewhat. So assuming ISO files have more random noise, these bits would be more difficult to compress therefore larger files would result.

[fwhitesides]

So assuming ISO files have more random noise, these bits would be more difficult to compress therefore larger files would result.
Ah, that makes sense. Thanks.