big advantage Canon The S45 has more flexibility in movie modes. It has 2 movie resolutions in AVI format (more versatile), while the Olympus has only one mode and it is a QuickTime format

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moderate advantage Olympus They both have rechargeable battery capability. The S45 comes with a proprietary rechargeable while the Olympus uses AA batteries and you can get a plethora of rechargeable AAs inexpensively.
moderate advantage Canon the Canon comes with a 32MB card. The Olympus comes with a 16MB card.
Big advantage Canon The Canon uses Compact Flash cards of which you can get up to 1GB of memory, or you can even go higher with IBM MicroDrives. The Olympus uses Smart media and this is capped at 128MB.
Draw The Olympus has a more dynamic lens, while the Canon has more preset settings for different situations (portrait, night, panoramic, etc). This makes the Olympus simpler to use, while the Canon has more modes to set the camera up in.
moderate advantage Olympus The Olympus is about $50 cheaper than the S40 and 70-100 cheaper than the Canon.
Very minor advantage Canon The Canon has a 3X optical/3.6x digital zoom. The Olympus has a 3X optical/ 3.3x digital zoom.
Personally, I would go with the Canon. It is a little more expensive, but it has more options and you can get a much larger memory card for it. It also comes with a rechargeable, and cameras EAT batteries like mad. If it were me, I would order another battery from Canon. The battery directly from Canon is $70 (part NB-2L). You can get a lot more accessories for the Canon as well, including an underwater case for water photography. (That is just really cool!

) The only thing that would make me hesitate is the price on the rechargeable. You can get a set of 4 rechargeable AA batteries for less than $10 and there are even solar rechargers for them, in case you are out at the beach or somewhere away from an energy source. In the end, the larger memory card and more options makes me lean to the S45.
Hope this helps.
Dave
PS- I have the Canon S20, 3.3MP Canon and love it. I only wish it did movies and I wish I had one more battery. But the camera is over 2 years old and was one of the first 3.3MP cameras. It still does great work and has traveled all over with me throughout the southeast and to Europe!
Main Sources:
http://www.steves-digicams.com/2001_...canon_s40.html http://www.steves-digicams.com/2002_reviews/c4000.html http://www.powershot.com/powershot2/s45/accessory.html http://www.batterymart.com/merchant2...=rechargeables