I purchased a Canon EOS Digital Rebel many, many, years ago. It came with some great software that allows you to control the camera from your PC, handle their RAW format, their photo organizer, etc. The problem that I encountered recently is that all of the software, while compatible with OS-X, per-se, is for the PowerPC architecture. Since Rosetta has been dropped from OS-X (I'm still on 10.7), you can no longer use PPC binaries and, consequently, the Canon software won't install.
What to do?
You can go to the Canon site and find the software download page for your camera. The problem is that Canon only makes available 'updaters' for their software. The updaters first inspect your system to be sure that some form of the Canon software has been previously installed on your system. If you are like me, with a new mac, then you are out of luck, as the software won't be found and the updater will refuse to run.
There are apparently images of newer Canon CDs on the torrents. I found one on rutracker.org. The site is in Russian and, if you use Google Translate on it, registration does not work. Cut and paste text from the site into Google Translate manually, and get yourself registered. Then search for 'Canon Disk'. Then you'll find various disk images thoughtfully made available by our once cold-war enemies.
Choose the one you want and download the torrent file to your computer.
Once you have that file, double click on it to have your bit torrent client open it and read it. Confirm availability (seeds) and download. In my case, since I only wanted the OS-X software, I used my torrent client (Transmission) to ignore the Windows software contained in the image so that it wouldn't be downloaded.
Ten minutes later, I had the software on my mac, ready to install. I haven't bothered calling Canon to see if they will provide a non-PPC version of the software because, even it it's free, it will take longer than I'd like to wait to get it. Technically, this is theft, I suppose.
After installing the software, the software says it can't see any camera. More research on the net.
I find a great post at http://www.justanswer.com/video-camera-repair/7lqw0-greetings-i-proud-exhausted-owner-canon-5d.html that more or less explains that firmware updates to the camera are obtained and installed by ImageBrowserEX. That software was not included in the disk image downloaded above. There is an updater for IBEX on the Canon site. Not again! I found a link to a complete image of IBEX at http://gdlp01.c-wss.com/gds/1/0200002341/01/ibxm-inst-1-1-0-17-u01-9l.dmg.gz which I downloaded and installed.
Upon running IBEX, I get another 'No camera found' error. Somewhere I see a comment about putting the camera on 'play' or viewing an image on its display. I view an image on the camera back and run IBEX again. This time it goes through an installation sequence. IBEX downloads additional software from Canon, but doesn't tell you what it is.