The WILL differ. Whether it differs much, or enough, is a subjective matter. But they WILL differ. The 300/4 will have a different field of view than the 200/2.8 will, and cropping will not change that. There is no way around that. The background material will be different between the two images. Its the physics of focal length and cropping doesn't change that.
Thanks for that.
I have no idea myself.
I just wonder if it could be a viable alternative for the OP. I have never used a 200 f/2.8 myself. The numbers seem to indicate to me that it might be worth a try. The only thing is lack of IS may make it a poor choice for the intended use.
Thanks for all the replies you all bring up good points, however I do currently own a 300 f4 also I do nothing to my photos before handing them in they take care of all editing to them. I think i am going to go with the 7d after a lot of research I think it will accomplish my needs again thank you all for helping me.
I disagree. The operative word here is isolation. Let's look at some DOF numbers.
With a subject 75' away:
200mm, F2.8: DOF = 4.55'
300mm, F2.8: DOF = 2'
Note the 300mm has less than half the DOF of the 200 in this example. That will make a huge difference in your ability to isolate your subject from the other players.
Also, when you crop an image to increase magnification, you also increase noise. So really, you're not even coming close to what the 300 would look like.
:hide
I take your point, but it also depends on other variables not mentioned here; as I said, I wasn't sure if it was relevant to the OP's situation (he confirms it isn't) BUT I have frequently shot with the 135 at f2, and then cropped it in to get results similar to those taken with a longer lens ... with resulting excellent isolation, bokeh and no significant "naked eye" increase in noise (assuming decent exposure to begin with). WIll a cropped shot with a 200mm look exactly like a shot taken with a 300mm? Of course not. But - depending on other circumstances - it might have provided solutions for *some* situations, and the 7d does allow deep cropping without significant degradation of image quality. That's all I was pointing out!
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Thanks for that.
I have no idea myself.
I just wonder if it could be a viable alternative for the OP. I have never used a 200 f/2.8 myself. The numbers seem to indicate to me that it might be worth a try. The only thing is lack of IS may make it a poor choice for the intended use.
:hide
I take your point, but it also depends on other variables not mentioned here; as I said, I wasn't sure if it was relevant to the OP's situation (he confirms it isn't) BUT I have frequently shot with the 135 at f2, and then cropped it in to get results similar to those taken with a longer lens ... with resulting excellent isolation, bokeh and no significant "naked eye" increase in noise (assuming decent exposure to begin with). WIll a cropped shot with a 200mm look exactly like a shot taken with a 300mm? Of course not. But - depending on other circumstances - it might have provided solutions for *some* situations, and the 7d does allow deep cropping without significant degradation of image quality. That's all I was pointing out!