I wouldn't get a Point & Shoot if you intend to take stock.
You'll want a camera that can take at least 6MP images. Most professional Stock agencies/resellers (for example, Alamy.com) require at least a 45Meg image file. A 45Meg TIF file is about 15MP. In order to interpolate that high (with a program such as Genuine Fractals) you're going to need a decent sized image to start with.
The Nikon D100 & D70 take 6.1MP images (3008x2000 pixels). Usually I'll upsize to 12032x8000 pixels using Genuine Fractals Pro, then do a little tweaking, and use Adobe Photoshop's bicubic resampling to knock it back down to 6016x4000 (24MP) then some final tweaking to get about a 70Meg TIF file to go to stock agencies.
Megapixels is the number of pixels that make up the entire image. But, this alone is not the major factor in choosing a camera. I've had better 6x4 prints from a Sony Mavica FD-83 (a 5 year old camera that does 1MP) than I've seen some HP cameras produce at 3-5MP.
It's about the quality of the sensor, and the quality of the lens used in the camera.
If you're wanting to take photography seriously, and want to try to make a living out of it, I wouldn't go for anything other than a Digital SLR (if you're dead set on digital).
This can get expensive. You're looking about US$1500 for a good BASIC digital SLR setup (new Nikon D70 or used Nikon D100, 18-70DX lens, 1Gig CompactFlash, all the way up to tens of thousands of dollars in total for a top of the line DSLR body (Nikon D2x, Canon 1D Mark2) and a good quality lens (like the Nikon 200mm f/2.0 AF-S VR lens for $4500, or the 200-400mm f/4 AF-S VR zoom for $5500), a couple of flashes ($350 a pop for the SB-800), few hundred bucks on filters, etc.
So, I'll ask the same question criserb did. How much are you looking to spend? If you're not looking to spend at least $1,000, I'd forget taking photos for stock. Most of the reputable agencies won't even look at them.
Btw, outside of the Asian market, the "IXUS 500" is called the Canon Powershot S500 (Just for searching prices). If you just want to take snaps, then it's a pretty good camera. But, I'd also look at Nikon & Fuji point-n-shoots in a similar price bracket. The best way to see which is right for you, is to just head down to the camera store, hold them, and see which feels right and takes good quality shots.
Take a few shots, and have a look at them on your screen when you get home. Don't buy the camera straight away, you can never really see how good a digital camera's picture quality is just by seeing the image on the LCD display. Take the pics home from the various cameras, look at them on your screen, do a little more research, then make your determination as to which you want to get.
John
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