I want SLR camera only for clarity of and depth of picture

They are 2 very different cameras, but can produce stellar images with the right glass and technique. That said, you will find it easier to produce great images with the D90. Now, before I get stoned I shall explain. The sort of person who buys a 550d or D90 is not going to splurge on high end glass. They probably will end up with kit glass and maybe a prime 35 or 50mm. With 12mp the D90 will allow the user to make mistakes in their technique and will be fine with run of the mill glass. With 18mp on the 550d though, you're going to see flaws in the glass and technique and thus a beginner may just be disappointed with the 550d. I've seen far too many soft and out of focus images on the net and believe technique, glass and a lack of understanding is to blame

If you want real clarity and depth nothing beats the sigma's Foveon sensor. Period. For low light the Nikon suggestion would be much better.

Hi there. There is something film like and somewhat magical about how photos come out with the Foveon sensor. Be prepared to read many negative comments, not about the image quality, but the way the camera has been put together - slow to work with, low light issues, low pixelated back screen, no image stabilizer etc etc - as it's a camera you need to put work on, it makes you think, and with some patience the rewards can be fantastic. Link of Flickr page with pics taken from Sigma DP1/DP2 cameras: aml-1 at www.flickr.com Direct Sigma link: cameras at www.sigmaphoto.com These almost pocket size camera models have recently been upgraded with the 'Merrill' name on them but you can find the older models cheaper on eBay and worth it for a rewarding photographic experience. Also search for them on google. Enjoy the read :)

really?now I know... I just have D5000 here so I thought that was too low