Welcome to my astronomy blog, I dedicate myself to the simplest form of amateur astronomy which requires only portable equipment. I have two small refractors, two small binoculars, one small GOTO mount and another small equatorial mount, and a small H-alpha solar filter. Originally from a city where the people were proud of their light pollution, that is Hong Kong where I loved. Relocated to the UK since 2021.
Thursday, July 16, 2009
Round 3: Canon 100-400mm @ 400mm vs. Canon 200mm 2.8 with Kenko 2x
Canon 450D at ISO 200, two lenses were tested again each others namely, both lenses are having date code beginning with UW:
1. Canon 100-400mm f4.5-5.6L USM
2. Canon 200mm f2.8L USM + Kenko 2x
Zoom at f5.6, center cropped:-
Zoom at f5.6, border cropped:-
200mm with 2x at f5.6, center cropped:-
200mm with 2x at f5.6, border cropped:-
Zoom at f8, center cropped:-
Zoom at f8, border cropped:-
200mm with 2x at f8, center cropped:-
200mm with 2x at f8, border cropped:-
Summary: center sharpness of the prime with 2x is similar to that of the zoom, but the border sharpness of the zoom is clearly superior!
Final test on the sun with Thousand Oaks Type 2+ Glass filter, all cropped:
200mm with 2x wide open:-
100-400mm at 400mm wide open:-
The one from the zoom has a more well defined edge, it could be a result of the IS of the zoom but from my previous experience, even when I put the 200mm with 2x on a tracking mount, the edge is still a kind of fuzzy, so it's very probably that the zoom is performing better indeed. More tests should follow.
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