07-29-2011, 02:55 PM
[quote name='Frank' timestamp='1311950095' post='10310']
I don't understand why photozone does not test Tamron 200-500 again (on FX body). In certain sense this is a charming lens since it has an attractive focus range, it is not expensive but has a good IQ, and in addition it has a very light weight in the class.
Frank
[/quote]
The reason for longer lenses not being tested, is that the longer the lens is, the bigger a distance is needed between camera and focus charts. The focus charts are designed to fill a certain amount of the image... so the longer the focal length, and the higher resulting magnification, the bigger the distance between camera and subject needs to be.
And you do need to have the room indoors to be able to test that like you test the other lenses...
Suppose the test charts are designed to be 51x the distance of the focal length from the camera. 500mm would then need 51 x 0.5 = 25.5 meters. Add some space behind the camera too. I certainly do not have the space (26 meters minimum!).
The biggest space i have available is a bit over 7 meters, and that is without a blind wall on either end!
I don't understand why photozone does not test Tamron 200-500 again (on FX body). In certain sense this is a charming lens since it has an attractive focus range, it is not expensive but has a good IQ, and in addition it has a very light weight in the class.
Frank
[/quote]
The reason for longer lenses not being tested, is that the longer the lens is, the bigger a distance is needed between camera and focus charts. The focus charts are designed to fill a certain amount of the image... so the longer the focal length, and the higher resulting magnification, the bigger the distance between camera and subject needs to be.
And you do need to have the room indoors to be able to test that like you test the other lenses...
Suppose the test charts are designed to be 51x the distance of the focal length from the camera. 500mm would then need 51 x 0.5 = 25.5 meters. Add some space behind the camera too. I certainly do not have the space (26 meters minimum!).
The biggest space i have available is a bit over 7 meters, and that is without a blind wall on either end!