Cropping the 5D to match 20D

[leebase]

My 5D arrives today -- woohoo! I'm keeping the 20D as my backup/second camera, and the digital rebel goes into standby mode.

I'll eventually be able to answer this for myself, but I'm wondering for those of you who have already dealt with this:

How much better is a shot on the 20D at the telephoto end, than the same shot on a 5d which is cropped?

When I first held the 5D and looked through the "big viewfinder", I was actually a bit disappointed. The viewfinder is big, but the subjects in the viewfinder are the same size as they are on my 20D. There is just MORE in the view finder.

That's when the "it's a crop factor stupid" -- hit me. My Sigma 70-200mm f2.8 is not a "320 equiv." on the 20D. It's just the same, but the view is cropped. I "knew" this before, but it sure SEEMED to be longer.

One of the reasons I went for the 5D was the better AF -- not so much that it was full frame. As such, it seems to me that I'd want to use the 5D even for sports, and just crop if needed.

I know, the fps is slower, but I rarely shoot off 5fps bursts even with my 20D -- that's just not how I shoot sports.

Lee

[Seefutlung]

A full frame cropped sensor beats a cropped full frame sensor (is what I have read).

[mercphoto]

One of the reasons I went for the 5D was the better AF -- not so much that it was full frame. As such, it seems to me that I'd want to use the 5D even for sports, and just crop if needed.

I know, the fps is slower, but I rarely shoot off 5fps bursts even with my 20D -- that's just not how I shoot sports.
A little basic math answers your question. The sensor on a 20D is 40% the area of the sensor on the 5D. So if you crop a 5D to the area of the 20D you toss away 60% of the pixels you start with. 40% of 12.8 million pixels is just over 5 million pixles. But the 20D has just over 8 million pixels.

If you're gonna crop you are better off with the 20D. I also think the 20D AF is better for sports (so I've heard). 5D appears to be better at dim light focusing.

For sports I'd keep using the 20D.

[leebase]

A little basic math answers your question. The sensor on a 20D is 40% the area of the sensor on the 5D. So if you crop a 5D to the area of the 20D you toss away 60% of the pixels you start with. 40% of 12.8 million pixels is just over 5 million pixles. But the 20D has just over 8 million pixels.

And, as I have a 6mp digital rebel, I can say that for most prints the difference in 6 to 8mp doesn't matter that much.

If you're gonna crop you are better off with the 20D. I also think the 20D AF is better for sports (so I've heard). 5D appears to be better at dim light focusing.

For sports I'd keep using the 20D.

That will be really sad if true -- cuz the 20D AF isn't great. Better than the rebel for sure -- but I haven't found it to be "all that".

But I guess I'll find out for myself soon -- thanks for the input.

Lee

[Seefutlung]

And, as I have a 6mp digital rebel, I can say that for most prints the difference in 6 to 8mp doesn't matter that much.

It takes approx. 50% more MPs to see a visual difference in IQ.