I have not seen a review of the SD400 so far.

Here is a review of the SD500:

http://www.steves-digicams.com/2005_reviews/sd500.html

The quality and detail of the sample photos is excellent.

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From the specifications, it appears that the SD400 is about the same as the SD300, but with 5 megapixels.

The SD500 appears to be set apart from the other SD cameras. It is slightly thicker and appears to have a different lens.

I read somewhere that the SD500 has the lens from the S500 camera. And that is an excellent lens.

The SD500 has a more powerful battery than the other SD cameras.

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If you are not in a big hurry to buy, I would wait until some reviews of the SD400 show up ... Then make your decision ... SD400 or SD500.

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