Quote Originally Posted by Daniel Browning


Do you need 1000 horsepower or 500 horsepower? Do you need 1000 watt lights or 500 watt lights? 1/1000 or 1/500? 1000 ISO or 500 ISO? A single stop is a big difference in depth of field and light gathering power. As a self-confessed aperture addict, it's contrary to my nature to ever recommend anything except the lens with widest aperture, so I say go with the 2.8.


However, I will add a side note: for all overlapping fields of view, the 5D2 with the 70-200 f/4 will have slightly more light gathering power (better low light/underexposure) and thinner DOF than the 50D with the 70-200 f/2.8. That means the faster f-number is even more important on the 50D than after you upgrade.
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Thanks Daniel. I always enjoy reading your posts and appreciate your perspective. It's looking like I am going to continue saving so that I can buy the f/2.8!