I wrote an article a couple months back on whether the 300mm lens was enough. Click below to see that post.
In this article I didn’t want to get into the technicalities of using a 300mm vs. 400mm on the field but rather show you some images taken in the same setting using the same camera with both lenses. I did this mainly to illustrate how similar the “look” of both lenses can be and to sort of eliminate the anxiety that some 300mm 2.8 lens owners have of missing some sort of magical quality from their photos because they don’t own a 400mm. As I said in the previous article, the difference between the two in terms of compression/ background defocus and depth of field is primarily related to proximity. Of course at the same distance and same F-stops there will be noticeably more compression and subject background separation if you were doing a comparison with both photos placed next to one another but not as great as some would assume. In other words that beautiful look that you see in the photos taken with the 400mm lens is achievable just by being a bit closer (about ten yards) to your subject with the 300mm.
Below are photos from two football games, both played at the home field of the Philadelphia Blue Flame. Both were photographed on the same field under generally the same lighting conditions and general camera settings with the same Canon 1DX camera.
The first set was taken with the Canon 1DX and the 400mm 2.8 prime and the second set with the Canon 1DX and the 300mm 2.8 prime.
Note: Both the 400mm and the 300mm 2.8 primes are the older non IS versions.
These game photos were taken with the 400mm 2.8 lens @f3.2
These game photos were taken with the 300mm 2.8 lens @f3.2