You are correct for ZoomBrowser. I ran EOS Utility assuming that was
the correct app. It behaves as I said. But EOS Utility is the tethered
shooting utility which is why it requires attachment to the PC. It
does, of course, download the image to the PC but that's a related and
not its principal reason for existence.
Anyhow, your statement that the downloader did know the files had
already been downloaded caused me to think a bit harder. I haven't had
to think about internal FAT file structures since about 1987 but I just
realized how the downloader must work in order to recognize that the
file has already been downloaded. I had completely forgotten about the
"archive bit" in the FAT file system. Each file has one byte available
for file attributes and one of the bits is called the archive bit. I
looked up this tidbit to refresh my memory.
-----------------------------------------------------------------
Archive: This is a special bit that is used as a "communications link"
between software applications that modify files, and those that are used
for backup. Most backup software allows the user to do an incremental
backup, which only selects for backup any files that have changed since
the last backup. This bit is used for this purpose. When the backup
software backs up ("archives") the file, it clears the archive bit
(makes it zero). Any software that modifies the file subsequently, is
supposed to set the archive bit. Then, the next time that the backup
software is run, it knows by looking at the archive bits which files
have been modified, and therefore which need to be backed up. Again,
this use of the bit is "voluntary"; the backup software relies on other
software to use the archive bit properly; some programs could modify the
file without setting the archive attribute, but fortunately most
software is "well-behaved" and uses the bit properly.
-----------------------------------------------------------------
Presumably the Canon downloader is acting as a backup app and clears the
archive bit when it downloads a file. Before downloading again it notes
that the archive bit has been cleared. But I don't believe that
DownLoader Pro behaves the same way. For a generic app to be used
across camera platforms I don't know if one can assume that the archive
bit has been set by the camera when the file is first created. But it
probably can be as it's something that should be done by the file
system's "close" API if the file had been open for writing.
Dr. (poor) Memory
On 10/4/2010 5:32 AM, Moose wrote:
> On 10/3/2010 6:10 AM, Chuck Norcutt wrote:
>> I just tried to used the Canyon download software and gave up. It
>> apparently wants the camera connected via USB cable. No other
>> option. Boo on Canyon.
>
> You are quite wrong. I've been using ZoomBrowser for many years, and
> never, to the best of my recollection, connected to the cameras
> involved for a download.
>
> Click on top button/box on left, "Acquire& Camera Settings." then
> click on button/box "Acquire Images from Memory Card"
>
>> Also boo on Canyon for a really crappy interface.
>
> Can't really speak to that. I've been using it so long it makes
> perfect sense to me.
>
>> But I see the downloader does have an option to download all or
>> download those not downloaded yet.
>
> There is also an option to select individual images for download.
> I've downloaded something around 15,000 images from memory cards in
> readers with this app, so I'm pretty sure it works. :-)
>
> If you opt to download image files already in the destination, it
> downloads an additional copy, with an added numeral at the end of the
> name, rather than ignore the download or write over the previous
> copy.
>
>> Why not do a simple test with a few files A, B, C and D. Download
>> A and B to computer #1. Go to computer #2 and select download
>> those not downloaded yet. See what happens.
>
> I just tried something like that. I took a card that I had downloaded
> to portable computer in Maine. I've since copied the files to the
> desktop using Syncback. I created a new directory on a different disk
> on the desktop and tried downloading the images in subdirectories by
> date. It said all images had already been downloaded, would I like
> to download them again.
>
> I don't see any index files on the card, so I'm not sure how they
> keep track, but it certainly seems to work, as that card hadn't been
> connected to the desktop since being formatted.
>
> Moose
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