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Re: [OM] odd CF card (or E3) behaviour

Subject: Re: [OM] odd CF card (or E3) behaviour
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Fri, 02 Jul 2010 20:49:27 -0400
Ok, I'll try to make as much sense of this as I can.

In case 1 the scenario that makes most sense is that the card reader has 
a problem.  I would normally say that the files on the card were 
corrupted except you say you could view them on the camera.  If so then 
the images on the card had to be good.  Since we won't hypothesize that 
all 3 computers were bad the only common thing between them all is the 
same card reader.  But there is still a possible fly in the ointment 
here.  When you say you could view them on the computer do you mean as 
in successively reviewing images in playback mode or was it just seeing 
them pop up on the screen as they were shot.  If the latter you could 
have been viewing just an image in the buffer that had not yet been 
written to the card.  If that were the case the card could still have 
been corrupt and you wouldn't have known it.  That would put the error 
back on a corrupt card.

Case 2 is a total mystery to me except for hypothesizing an error in 
finder since another app, iphoto, is able to display an entire image and 
also export it intact.  That says the image on the card had to be there 
in its entirety and was successfully copied to the computer.

But surely there is also a case 3?  You say you lost *all* of your dance 
images even though you could recover older images with recovery 
software.  Losing all of your just shot images is consistent with having 
lost the directory.  That could happen if the camera was writing and 
lost power or if the card was removed before the writing was done.  The 
last thing that's written is the directory update to say where all the 
files are located.  But that *shouldn't* happen with a normal power off. 
  The camera is supposed to ignore power off until its done writing.  Of 
course, if you pulled the card out of its slot before writing was done 
the camera has lost control and you've lost your images.

Now then, why did the recovery software find old images.  It's because 
there was still an old copy of the directory there and you deleted 
images rather than reformat.  Deleting or erasing images doesn't 
eliminate the directory entry that points to that image.  It only marks 
the entry as deleted without actually erasing anything.  The original 
entry is still there.  The camera's file system knows enough to ignore 
the entry because it's marked as deleted.  But the recovery software 
says, "Oh, Siddiq wants me to recover all this old stuff that's marked 
deleted."  And that's what you got.  Your original images are probably 
still there too but, because there was a valid but obsolete directory 
there, that's what the recovery software picked up on.

More advanced recovery software could probably get them back but it 
needs to know enough to scan the files themselves rather than the 
obsolete directory.  If you had formatted the card rather than erased 
files the recovery software would probably have picked up both the new 
and old images but wouldn't know their camera assigned file names.

But I still can't explain everything to my complete satisfaction.  I'm 
still bothered by the abberant behavior of the finder.

Chuck Norcutt



siddiq@xxxxxxx wrote:
> On Jul 2, 2010, at 3:39 PM, Chuck Norcutt wrote:
> 
>> I'm having trouble here since parts of the story (as I understand
>> it) don't seem to add up.  The clarifications you've added on this
>> message and the previous one say the problem exists with the images
>> as they are stored on the card because the corrupted images move
>> wherever the card goes.  Or is it maybe the reader?  Does the
>> reader move with the card? If that's true it's the camera, the card
>> or the reader... it can't be the computer.  However you have also
>> stated that, after a download, images on the same computer
>> displayed by one application are corrupted but on another
>> application they are not.  That says one of the apps is corrupting
>> an otherwise fine image.  It can't be both ways... or if it is you
>> have a truly confused problem scenario.
> 
> Sorries, was posting about two diff times this happened. The first
> time (last month or so), all the pics on card, in camera, looked ok.
> Put card in cardreader, Mac saw partial images (most were less than
> 1/4th). Same card/reader on another  mac, and finally a PC, same
> results, partial images.
> 
> 2nd time (yesterday), images reviewed on camera fine, but on mac
> showed as partials in finder, complete in iphoto. if i exported them
> out of iphoto (after importing them), they showed up complete images.
> 
> 
>> You haven't used any recovery software on this card have you?  The
>>  scenario you describe (some JPEG images are truncated) can happen
>> if you delete images on the card while you're shooting and the
>> directory is later lost due to reformatting or other problems.
>> With the directory gone or damaged the recovery software may not be
>> able to figure out where some images start and end because (due to
>> the intermediate file deletions) the image storage may not be in
>> contiguous clusters.  Trying to read these back may produce only
>> the first part of an image leaving some amount of the bottom
>> portion chopped off.  The rest of the image is probably still there
>> but the software can't figure out which intial image fragment it
>> belongs to.
> 
> The only time I ran recovery app was when I lost the entire dance
> shoot. Couldn’t recover any dance images (oddly, could recover photos
> from prior shoots). I rarely delete images on camera, and never via
> Explorer/Finder. Standard procedure is to first copy or import all
> the photos to computer, put card back in E3, and delete all (or more
> recently, format card, just because). I wonder if turning off the
> camera right after a burst of images had anything to do with it? It
> was just a power off via rear switch, not a battery-dying power off.
> 
>> Chuck Norcutt
>> 
>> 
>> siddiq@xxxxxxx wrote:
>>> On Jul 2, 2010, at 2:09 PM, Chuck Norcutt wrote:
>>> 
>>>> Now I'm totally confused.  The first part says the images were
>>>>  transferred to the computer OK but something unusual happened
>>>> to them after they got there.  The second part says the problem
>>>> moved to a different computer along with the card and reader.
>>>> Got a different card or reader?
>>> The first time this happend (last month I think), I did try
>>> taking the card/reader to a PC and another Mac to eliminate my
>>> own machine out of the loop. all three machines showed the same
>>> partial image. Mac 10.5, 10.6 and WinXP/sp3
>>>> Also I don't know what it means (physically) to "re-export" an 
>>>> image from the iphoto library on a Mac.  I don't know if that
>>>> means the image was physically copied to a different place or
>>>> only that a pointer to it was handed off.  There are different
>>>> implications of each.
>>> importing copies to the applications photo library/database, so 
>>> diff/new file, not a pointer to the same one
>>> 
>>>> Chuck Norcutt
> 
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