Corrupted RAW files

Question

Hello all,
After taking about 10,500 pictures (99%+ in RAW) with a Canon EOS 20D since getting it last August, my two most recent imports to Aperture have shown some corrupted images.
My usual workflow is to copy the images to my hard drive, run the Adobe DNG Converter (v3.3) on them (to reduce their size), burn the original RAWs (.CR2) to DVD and remove them from the hard drive, then import the DNG files to Aperture.
This time, I've seen half a dozen files with visible corruption. It looks like a block of pixels, approximately square (although several of them may be adjacent to one another making the corrupted area look like a rectangle or an L).
On one of them, I located the original RAW (.CR2) file and also imported it. That file is actually NOT corrupted and looks just fine.
So, I don't know what the problem may be. It could be any of these listed next. Perhaps anyone has seen this and resolved it before?
*) DNG converter messed up the conversion
*) Disk corruption on the DNG file
*) Aperture doesn't read the DNG file correctly (although I've tried both 1.0 and 1.1)
*) Something else I haven't thought of
I welcome any thoughts on the matter.
Thanks,
Doug

Answer 1

Doug, I have been experimenting with the DNG format lately and how Aperture handles it. I have a Nikon D2X and shoot 100% RAW. Normally, I bring my .NEF RAW files from the memory card directly into Aperture. Importing the RAW files directly this way has been no problem. Neither has first copying the RAW files from the camera card to my hard drive, and then importing them into Aperture.
However, I have been using another program lately that enhances the RAW files from my camera, and the only RAW format it outputs is DNG. So naturally, I have run a number of my RAW files through this program, created the DNGs and imported them into Aperture. The results were not pretty. The imported DNGs were no bigger than a thumbnail with added noise and visible distortion. I have also read these exact same DNG files into Adobe Camera Raw and they were rendered perfectly.
I next converted the same original RAW files to DNG using Adobe's DNG converter (both 3.3 and 3.4) and read them into Aperture. The Adobe converted DNG files were all fine. No visible signs of problems even at the highest magnification.
I presume that you have tried reconverting the same RAW files to DNGs again and retried the import into Aperture with the same results.
I think your first and third conclusions on what is wrong were right. There is something about the makeup of the original pictures that the DNG converter can not handle properly. This problem is not enough to affect working with these DNG files in Camera Raw, but it is for Aperture. Aperture seems to be especially sensitive to how DNGs are constructed. The slightest thing wrong with an image file (either in its construction or EXIF information) and Aperture can not properly process and render the image.
I would say that disk corruption is very unlikely.
Until DNG is fixed in Aperture, I will only import my native RAW files into Aperture.
Jeff Weinberg