04-19-2017 11:36 PM
I just purchased the 1D Mark IV (Used) and have been having trouble with the SD cards. I think I may have figured out what is wrong but can someone kindly confirm my thoughts...
I purchased a SanDisk Extreme Pro 64 GB SD XC card Class 10 with 95 MB/s speed. When I placed the card in the slot, I kept getting a message that the card could not be accessed. Therefore, I could not format the card either. I was originally thinking the slot may be bad, but when I placed a microSD card with the adapter in, the card read and I was able to take some pictures. I then thought the card was bad after trying to format it on a friends Mac Book and got the same type of message, indicating that it could not access the card.
I received a replacement card from Amazon and when I put that card in the slot, it too was not accessable. I finally tried a 32 GB SD HC Class 10 card which I knew worked and it was immediately recognized.
My question is does the SD XC card not work in the 1D Mk IV? I did look in the maual where I found the info regarding the SD HC card.
Also, what is the largest SD card I can use? I have not been able to find a 64 Gig or larger card that is not an XC. HC only seems to go up to 32 Gig.
Thanks in advance...
Solved! Go to Solution.
04-20-2017 06:19 AM - edited 04-20-2017 06:24 AM
1D Mark IV is not compatible with SDXC cards.
32GB is the largest size SDHC card; that is what you want to use.
04-20-2017 06:34 AM
SDHC cards are good. SDXC and micro-SD cards are bad. Use a maximum size of 16GB or 32GB in each slot, and make them match in size, too.
04-20-2017 07:01 AM
04-20-2017 06:13 PM
The difference between an SD, SDHC, and SDXC is really more about the filesystem type.
The original standards were based on the same filesystem used by MS-DOS PC's (pre-Windows days) when filesystems used FAT12 (a filesystem originally designed for use on floppy diskettes - very small capacity). As computers started to get hard drives, it was still adequate provided the drive was not larger than 32MB (note that's MB -- megabytes, and not GB -- gigabytes).
The standard was revised to use a 16 bit FAT table (FAT = file allocation table) and FAT16 (vs. FAT12) could allow filesystems up to 2GB (instead of just 32MB). What would we ever do with so much disk space?
All "SD" cards (no suffix... so just plain "SD" and not "SDHC" or "SDXC") support either the FAT12 or FAT16 filesystem and if they use FAT16 then they are limited to 2GB.
Once we broke through the 2GB barrier, a larger filesystem type was needed. This came in the form of the FAT32 filesystem. This was still based on the PC filesystem but could now support filesystems up to 32GB.
All "SDHC" cards use the FAT32 filesystem.
But now we have even larger filesystems and a new standard was needed. On the Windows PC, they moved away from using the FAT filesystem and moved to to NTFS. The "problem" with NTFS isn't a technology problem -- it's a licensing problem. Microsoft wont allow anyone to implment a read/write implementation of their filesystem unless they pay licensing royalties. This not only creates a licensing problem for Canon, it also creates a problem for non-Windows users (e.g. Mac or Linux) who own these cameras but don't have a PC and thus are limited in their ability to use these cards. Apple came out with their own filesystem standard which they called HFS+ but they did the same thing Microsoft did with the licensing rules. No good neutral standard was available.
Ultimately a neutral standard was created ... named exFAT (extended FAT). This standard can support filesystems up to 2TB (terrabytes). I don't believe there are any 2TB cards on the market... but the filesystem can support cards that large.
Any card that has more than 32GB of space uses the SDXC standard and has an exFAT filesystem on it.
The reason your 5D IV camera can't deal with the larger SDXC cards is because it was created before the exFAT filesystem standard even existed. It doesn't have any firmware that understands the filesystem (I'm unsure if the physical card interface would have changed but it's also possible that it wouldn't be able to address that much memory even if it had updated firmware.)