Quote Originally Posted by Rubar View Post
Hi again!


So the test would have a camera with APS-C sized camera. For this test I believe there won’t be a big difference which model it is. Take 3 photos at a distance of approximately 300 meters (980 feet), but definitely all there at the same distance with the same camera:
1) one photo with EF-S 18-200mm f/3.5-5.6 IS Lens (or similar EF-S lens) at 200mm
2) one photo with EF 70-200mm f/4.0 L IS USM Lens (or similar EF lens) at 200mm
3) and one with EF 200mm f/2.8 L II USM Lens (or similar EF lens) which has fixed 200mm
4) unfortunately there is no EF-S lens with fixed 200mm, that I would know of.
If someone did this test, I suspect the results would be as follows. Each of the 3 shots would have a similar (or per Neuro's testing, maybe not so similar) framing of the subject at 200mm. Take 3 different lenses on the same camera at 200mm, and you will get 3 (at least) slightly different framings because of manufacturing variations. The focal length stamped on the camera is an approximation. But the variation shouldn't be major. And if you are looking for more reach, you need a lens with a longer focal length. It's not easy to capture subjects 300 meters away unless the subject is quite large.

Neither the 70-200 or the 200 prime will get you significantly more reach. For that you need a 70-300, 100-400 or a super tele prime lens.

For what it's worth, the hypothetical test would also yield quality differences....at 200mm, I suspect the 18-200 would have the "worst" IQ of the bunch, with the 70-200 and the 200 prime duking it out for the win, with the prime edging the zoom. Then, the f-stop selected for the test plays a role too -- not in how the photo is framed, but in terms of depth of field. The 18-200 at 200mm will have a max aperture of f5.6 (more depth of field); the zoom at f4 (less depth of field); and the prime at f/2.8 (even less depth of field). Depending on the focal point of the shot, the results from the three lenses could look quite different due the aperture setting. If all shots in the test were taken at f5.6 (the least common f-stop), the depth of field should be the essentially same in all three shots -- and I would suspect the prime would be an even easier pick for the IQ winner in that case.