For those who inexplicably believe that somehow using a 20D is better for birding because of the so called "reach", think again. You would be far more likely to catch that elusive albatros using a full frame camera because there is a bigger field of view to fit it in as it flies away. You can then crop that image by 1.6 and pretend you were so good that you captured the perfect composition with your 20D. And unless you want to print it 20 x 24, you'll have plenty of pixels left. And if you do there is always genuine fractals.
Don't tell me about pixel density or printing scenarios "a" and "b" of the same size. This isn't about some hypothetical reasoning, it is about humans viewing a finished image. And as for composing for the entire viewable frame of your camera, I don't necessarily think in the same ratio as the sensor. Besides, that concept is a throwback from film. Film prints start losing detail beyond the size of a contact print, so any cropping does indeed dramatically reduce resolution. With digital, on the other hand, unless you are making the maximum size print for your image pixel size, you are actually discarding resolution available for printing larger images.
The reality is that the only advantage more pixels will give you is the ability to print bigger pictures. There is no printer process that is able to show any more detail than is available to the 20D, or for that matter a 300D. The human eye is the real limiting factor. You cannot tell the difference between an 8 x 10 print made form virtually any high quality digital camera from a 300D to a Phase One back.
While I'm on a roll, stop using pre processed imagess as examples of how sharp or accurate your camera is. Digital images are meant to be processed. The difference is whether you let the camera do it or you do it yourself. There's a reason they call it "raw" and not "giant and perfect".
The only real advantage of the 1.6 sensor beyond cost is that since the lenses are designed to cover the field of a 35mm image, the weakest part of the lenses, the falloff of detail and distortion at the edges, is eliminated. Those edges are "cropped out" of the image.
I think my 20D is fabulous. I'd much rather have a FF sensor to take complete advantage of my lenses. Don't even try to tell me that I have more reach. I know I have less area.
Don't tell me about pixel density or printing scenarios "a" and "b" of the same size. This isn't about some hypothetical reasoning, it is about humans viewing a finished image. And as for composing for the entire viewable frame of your camera, I don't necessarily think in the same ratio as the sensor. Besides, that concept is a throwback from film. Film prints start losing detail beyond the size of a contact print, so any cropping does indeed dramatically reduce resolution. With digital, on the other hand, unless you are making the maximum size print for your image pixel size, you are actually discarding resolution available for printing larger images.
The reality is that the only advantage more pixels will give you is the ability to print bigger pictures. There is no printer process that is able to show any more detail than is available to the 20D, or for that matter a 300D. The human eye is the real limiting factor. You cannot tell the difference between an 8 x 10 print made form virtually any high quality digital camera from a 300D to a Phase One back.
While I'm on a roll, stop using pre processed imagess as examples of how sharp or accurate your camera is. Digital images are meant to be processed. The difference is whether you let the camera do it or you do it yourself. There's a reason they call it "raw" and not "giant and perfect".
The only real advantage of the 1.6 sensor beyond cost is that since the lenses are designed to cover the field of a 35mm image, the weakest part of the lenses, the falloff of detail and distortion at the edges, is eliminated. Those edges are "cropped out" of the image.
I think my 20D is fabulous. I'd much rather have a FF sensor to take complete advantage of my lenses. Don't even try to tell me that I have more reach. I know I have less area.
. I did a comparison between my 5D and 350xt with the 70-200 f2.8 on a tripod, focussed on a busy bird feeder about 25 feet away. Then I converted each image to 300 dpi, and then made them the same size to print and used my best sharpening strategies. Bottom line is that the image from the 1.6 multiplier camera (350xt) was sharper that the FF (5D) printed at the same size - visibly so on a bee that happened by. My wife, who is not technical at all said so, so don't argue 
