I've been staying with 2GB cards as well; partially because of the FAT32
performance hit but mostly because I think I'm risking too many eggs in
one basket above 2GB. Even 2GB is a pretty big risk but that has to be
balanced with less chance of suddenly needing a media change in the
middle of something important. Even shooting raw on the 5D it's still
good for about 160 images or the equivalent of about 4-1/2 rolls of film.
So, what's the risk, you might ask. Aren't CF cards extremely reliable?
Yes, but, as I discovered yesterday, I'm not. In the 28 years I've
been using personal computers I can't remember ever having accidentally
deleted a file. Until this past Saturday. I was shooting an event that
was broken into two parts. A morning session from 9:00-10:30 am and a
later dinner and party starting at 6:00 pm. After shooting the morning
session I came home and after lunch remembered that I wanted to do some
testing with a new flash. Without thinking that my CF card already
contained images from the morning shoot I fired of a half dozen shots at
nothing in particular, just to fire the flash.
After I finished the flash testing I wanted to get rid of the junk
images I had just taken and, without thinking again, I formatted the CF
card. No sooner had I pressed the button than I instantly realized the
error of my ways. Near cardiac arrest followed.
Fortunately, I didn't write anything over the top of what had already
been there and the Lexar CF recovery program got almost all of it back.
In the end I only had trouble with 4 images. One could not be
recovered beyond a thumnail. The remaining three could not be converted
from raw. However, the 5D raw file contains an embedded 4 MP JPEG and
the JPEG's were successfully extracted by BreezeBrowser.
In reviewing what happened with those problem images I noted the fact
that they were recovered out of sequence from the order in which they
were shot by a recovery program that was scanning the media
sequentially. I think those images were written in the empty spaces
that were created by deleting a few test images taken during the shoot.
My hypothesis is that, since these images were not the same size as
the original occupants of that hole in the file system allocation table
those files were not written sequentially in their entirety. Since
formatting destroyed the directory structure, a file that was stored in
two or more disjointed pieces had no way to be reconstructed since there
was no data or intelligence to link them together. When the damaged
files were recovered thay were significanlty smaller than they should
have been. All the pieces hadn't been found or at least linked together.
Anyhow, that's my hypothesis and it seems to explain what happened. But
its surprising if true since one of the major changes in the DOS file
system going all the way back to IBM PC DOS 2.0 (or maybe 2.1) was to
avoid reusing old, "empty" space if you didn't have to. This was
specifically to avoid the problem just described and make it easier to
recover accidentally deleted files. It tried to keep everything
contiguous if it could allocate enough contiguos space to do so and also
tried to use previously unallocated space if it could. In other words,
don't write over the top of previously deleted files until you had no
other choice. Since there was plenty of contiguous unused space on the
card I don't understand why that preiously allocated space was reused.
Me wonders if the verion of the file system implemented in the camera
has regressed.
In any case I don't think I will delete individual junk images anymore
while I'm shooting an important event. I'll just keep lots of CF cards
around and deal with the duds later.
Chuck Norcutt
Moose wrote:
>
> I've been staying with 2 gb cards so far, as they are generally faster
> than larger cards because of the difference in file system. (And B&H
> doesn't show the 4 gb cards just now.)
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