But does not the reach expand your subject in both axis/dimensions, therefore if you are talking surface area or % of the sensor covered, then what apop says is correct? Agreed, reach, but not % of sensor...Hey,
Since you have the 70-200 f2.8 , I would def. go for the 500mm f4 !
The 300 is superb off course, but it is pretty close to your 70-200 in reach.
The 500 is still hand holdable and since you use full frame cameras the choice of going for 500 for sports / wildlife is even easier ! (in my view)
I briefly had the 300f2.8 IS and 500 f4 IS, but got rid of the 300 f2.8
I found 300mm not long enough (even with 1.3 crop body)
I haven't checked this but i can imagine the appearance of a subject size between lenses (ratio) can be expressed as
500^2/300^2 = 2.777 times bigger (same distance a subject would appear 2.8 times bigger)
200 vs 300 = 2.5 bigger
200 vs 500 = 6.25 bigger
bigger meaning surface area of subject ( ratio's again)
Sorry if that logic is flawed, but i think it should be pretty solid since it's a 2 dimensional problem:P
Hope it is helpful
The logic is flawed, unfortunately - the resolving power depends on the focal length of the lens, not the length squared as it is a 1 D problem. Two lines can be resolved if the image on the sensor has them separated by two pixels. The size of the image depends on the focal length of the lens. So, a 300mm lens gives you 50% more reach than a 200mm, a 400mm 33% more than a 300mm, and a 700mm 16.6% than a 600mm, all things being equal.