1. I agree! Use a card reader to download the images from your memory cards. This is safer, better, faster than connecting the camera to the computer and downloading the images that way. Think of using the camera and USB cable as a backup that you only use in emergencies. (I also use the USB cable to access camera settings with EOS Utility, mostly to sync the clocks in several cameras, but occasionally for other things up to and including "tethered" shooting.
2. Be careful inserting Compact Flash cards in the camera and the card reader. There are 40 little pins in the camera that have to fit into 40 little sockets in the card. It has to be aligned correctly. Never force the card into the socket. It is possible to bend the some of the little pins in the camera so that it no longer works and repair is needed. That said, I've been using and insertinig CF cards into cameras for 20 years... certainly hundreds of times and possibly thousands of times... and never damaged one.
3. Don't "move" images off your memory card to your computer. Instead, "copy" them. This leaves the originals on the card temporarily, just in case something happens and the copies on your computer are corrupted in some way. Check that the downloaded images are good, before reusing the memory card and over-writing the original images. It's also highly advisable to back up all your images on your computer in some manner. "Stuff happens". Hard drives fail. Images may be irreplaceable.
4. Next time you go to use the memory card, use the camera's "Format" function before you start shooting new images. This "erases" all the old images and properly prepares up the card for new ones. Only "format" once you are sure that ALL the images you want to keep have been downloaded to your computer and safely saved.
5. Cameras have a limit on how large a card they can use. I don't know what the 20D's is, but you can probably find info in the user manual (free download from the Canon website, if you don't have one).
Personally I deliberately don't use the largest cards possible. Instead I use a number of mderate size memory cards that are nowhere near the max size. When I was shooting with 8MP cameras like the 20D, I used a bunch of 1GB cards. I forget exactly how many images I got per card. Now using 20MP cameras I use a bunch of 16GB and 32GB cards that hold 500 to 1000 images each. I don't "put all my eggs in one basket". That way if I lose a card or a card fails, I won't lose an whole day's work. I always wince a bit when I see people using one gigantic card in their camras, with days, weeks or even months worth of photos on it! If anything happens to that card, they'd lose a lot!
I currently have 18 memory cards for use in three cameras. I keep them in thseveral of those little clamshell memory card storage cases (that supposedly float, though I've never tested it). Face up cards in the case are ready for re-use, but still have old images on them. Whenever I swap one of those cards into my camera, I quickly use Image Review to confirm that the files on it are old ones I've already downloaded, then I format the card to "erase" them. It takes me abouit 10 seconds to swap out a card, check it and format it. I put the freshly filled cards face down in the memory card case, until I can download them later.
6. Also, it's a good idea to use a fine point, permanent marker to write your name, phone number and email on each of your memory cards... just in case you ever drop one and someone finds it. On another photo blog someone posted they'd found an unmarked memory card full of what appeared to be professionally shot wedding photos lying in the street! Fortunately, someone recognized the church in the photos and the person who found it got in touch with people there and was able to find the wedding party and photographer, to return their photos to them! Not everyone would go to that effort, so I think it's a good practice to write your name and contact info on your cards... just in case!
7. Okay, "quick" formatting a card in camera as described above doesn't actually erase the old images. It just marks them all as "okay to over-write" with new files. For this reason, should you ever acccidentally format a card before downloading the images, the images are probably recoverable... at least until you start over-writing them. There are special recovery apps that can be used (memory card makers like Sandisk and Lexar provide recovery software for free). Even if a few images have been over-written with new, some of the old images on the card might still be recoverable, if necessary.
Hope this helps. Have fun shooting!
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Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7DII (x2), 7D(x2) some other cameras, various lenses & accessories
FLICKR & ZENFOLIO
