format CF oddity

jchin

I took a 16GB Sandisk Extreme III 30MB/s CF card
and formatted in my 7D (firmware 1.2.1), it gave me
16,003,072 KB total disk space with 500,096 total allocation units on disk.

I took the same CF card and formatted in my 5D2 (firmware 2.0.4), it gave me
16,002,560 KB total disk space with 500,080 total allocation units on disk.

How can this be?

jchin

I just did the same test with my 16GB Kingston ElitePro CF card.

On 7D (firmware 1.2.1), it gave me:
15,757,184 KB total disk space with 492,412 total allocation units on disk.

On 5D2 (firmware 2.0.4), it gave me:
15,756,672 KB total disk space with 492,396 total allocation units on disk.

Can it be that the 5dmkII is programmed to format below the full capacity of the card?

pyry

Could be the cameras are handling, or reporting, bad block lists differently.

jchin

When I do a quick format on them in my Kingston 19-in-1 reader, they come back with whatever was set by the camera. The command I do from Command Prompt is:
FORMAT x: /FS:FAT32 /Q /A:32K

When I do not use the quick format (without the "/Q" option), they still come back with the same totals as what was previously set by the camera. If I format in the other camera, and do the non-quick format, it will reflect the size of that other camera.

It reflects whichever camera formatted it last. Very odd!

GadgetRick

Don't know if this is the case but, my guess would be, the cameras use different block sizes. That would explain the differences.

Or, I could be totally off base, in which case, disregard what I wrote.

jchin

GadgetRick wrote: »

Don't know if this is the case but, my guess would be, the cameras use different block sizes. That would explain the differences.

Or, I could be totally off base, in which case, disregard what I wrote.

Both are using 32K clusters.

hgernhardtjr

A simple difference in how each camera sets up various file folders or their naming schemes, or even camera-specific information added to your card by the camera when it does a format, etc. would eat up that small amount. That is one reason why many format cards in-camera as that ensures compatibility (although nowadays, that is not as much of an issue as it was several years ago).

BTW, if you do the math, it is not the normal rounding error engendered by using 1K=1000 vs. 1K=1024.

Remember, too, all a quick-format does is erase the already-created file markers and indicates the space is free ... it does not remove any data or change the pre-existing card structure. Hence the sameness you observed.

Anyway, 512K bytes difference does not make that much of a difference to picture storage and is nothing to worry about between the two different cameras.

JohnBiggs

hgernhardtjr wrote: »

Anyway, 512K bytes difference does not make that much of a difference to picture storage and is nothing to worry about between the two different cameras.

It's not significant as stated. I really wouldn't care if it was off by a whole megabyte.

pyry

I asked a couple of computing science friends and they said it could be a) some hidden data being saved or b) the partition borders being put in different locations.

Still can't say for sure though.