Just had my first time ever problem where a CF card (Sandisck 4GB ultra 2), would not mount on Desktop (Mac 10.4.1)

I solved issue by using Canon's software to get images off the card.

195 of the 200 large jpegs on card are fine. 5 are totally screwy looking -- like 1/2 a person's face and 1/2 image over bleached etc.

Question: all 200 looked fine on LCD during photo shoot.
My big worry in future: all 200 could look fine on LCD, and in fact be corrupted. Is this over panaoia?

It only takes one corrupted image to ruin your whole day. Since you are shooting JPEG, perhaps shooting RAW+JPEG could provide an extra degree of protection.

Windows XP often cannot recover CF card images (i.e. 'FAT' or 'FAT32' format) that Windows98 handles perfectly well. I recovered some for a user recently that had a 1/2-split image problem, and I just re-split them and pasted them back the right way. I may have had to do a rotation first, which can be messy, but the fixes were obvious at least.

One last tip - either "move" all pics from the card to the computer when finished shooting, or just reformat the card when done. The CF cards don't handle fragmentation as well as the computer hard disk, and corruption could occur by deleting some images and shooting new ones (and deleting and reshooting....)

thanks Tony,
Well, how do you know those Raws wouldn't have also been corrupted along with the jpegs?

the extra raws also defeat purpose of shooting just jpeg.

Dale:
Was this a fragmentation issue? Shouldn't one be ok after a re-format? or even if you forgot to reformat you should be ok. These cards are getting reformatted all time.

Not sure what your last sentence meant, but I never delete single images. I do a shoot, and then re-format right before the new shoot.

What about my initail question: Ever seen all you shots look ok on LCD and all be back in reality?

and why did the 5 bad ones look on on the lcd?

Isn't the initial display coming out of the buffer? If you then punch preview it will pull the image from the CF card. So the buffer would be fine but the write to the card could be iffy.

The transfer to the PC could also be hosed. So the info could be fine on the card but be corrupted on transfer. So the card could be bad. The card reader could be bad. The write to the card could have had issues. (Better hope that one was the card.)

Otherwise, cosmic rays or something.

The RAW and JPEG files are separate, so it is unlikely that they would both be corrupted.

There are many reasons to shoot just JPEG; there are many more reasons to shoot RAW. The only compelling reason not to shoot both would be to preserve buffer and CF card space.

I have never seen images that were corrupt and didn't show that in the Preview. My suspicion is that the corruption may have occurred afterwards; possibly by dropping the card (even a short distance) or exposing it to excessive heat or cold.

Unless it's a MicroDrive, dropping a CF card will not damage the images stored on it, nor will exposure to any temperature that you can survive. Flash-based storage is quite rugged; the only way you can corrupt data by shock is to hit the card hard enough to break one of the chips loose from its circuit board, and that requires a hammer blow or crushing force far greater than a simple drop will create. I have an Ipod Nano sitting next to me that survived a trip through the laundry (washer and drier) with no ill effects other than the battery meter reading being off due to some soap residue on the circuit board. After cleaning the interior with isopropyl alcohol, it is operating perfectly.

What's far more likely is that you were shooting with a low battery and your camera didn't have quite enough power to write the last few images properly, or you have a bad card reader or card reader drivers. It's also possible that your card is going bad. Using a different card reader, do a disk check on the card, and then copy some video files to the card to fill it as full as possible. Play back the video files from the card to verify that none of the files got corrupted. If the card will pass that test, it's fine.

I've had the same problem in the past. The comment about the low battery is a good one, I've found that issue myself too.

However I find that every time I empty my card, I am now in the habit of reformatting the card for a new shoot. Takes only seconds to do.

Since I have been doing this, I've not had any problems since (knock wood).
joe

Isn't it possible that the thumbnail portion of the Jpeg looks OK in playback yet the serious part of the image is corrupted? Viewing Jpegs on my cameras and zooming always looks different from the view on the computer. If you can, also try to do the equivalent of a 'scandisk' of the card, to check all data areas. BTW, whereas flash is not corrupted by magnetics as are mag disks and tape, they still have vulnerabilities, even tho rarely encountered. Static electricity is one, tho rare on CF due to the packaging, but still possible.

Yep.

Thanks Dark for outlining all those scenarious.

Thanks Tony, yeah, you nailed it: I shoot Raw a lot for what I consider important stuff. and large jpegs for quicker not as critical stuff. And doing both really slows things down still (Canon 5D), and makes the files even heavier.

But, I am real pleased to hear that if it looks good on LCD you are most likely ok. that's key. If everything is screwy I want to see that during the shoot. So hopfully those 5 were a fluke.

I'm buying a 2nd card reader, and will test that card on it first. Then I'll reformat that card as report on that.

I dowloaded right away afterward in studio, so not sure, but who know.. thanks.