What is the benefit on the FF body in terms of IQ?

[DNA]

I am one of them who are eager to see new 5D. Actually, the main reason to want full frame body is not only to get better image quality but also (rather) to get more useful lenses range. For example I don't like to use 70-200 on the crop body because its range starts from 110mm.

My question is how much full frame body has better IQ than the same mp crop body. If you use 12mp 5D and 12mp crop bodies(ex 450D), what kind of difference is between them in terms of image quality?

Sorry, if this question is old.

[Bob Atkins]

It's a complex question and it depends in part on which full frame vs which crop sensor.

I did write an article comparing the 20D and 5D which you might find useful.  http://www.bobatkins.com/photography/digital/full_frame_vs_aps-c.html