alundeb Online Upload & Sell: Off
|
Not that anyone cares, but I just had to check if the order of stacked teleconverters affects image quality. It appears it does. The best teleconverter or that one designed optimally for the lens should be closest to the lens.
My most TC friendly lens at the moment is the Canon 70-200 2.8 L IS II. The teleconverters used in this test are the Canon 2x III and the Sigma APO 2x EX DG. To be able to stack them in both orders (The Sigma can be stacked directly on the back of the Canon), I used a 12mm extension tube between the teleconverters. It was used in both setups.
Test wide open at 200mm x2 x2 = 800 mm f/11. Camera was Canon 5DS R. Images shown are unscaled pixel crops with zero sharpening.
In order to rule out focus errors, I used the EOS utility on my laptop and shot tethered in LiveView. Manual electronic focus by stepping through optimal focus one step at a time. This step can be done with a button. I stepped through many images, found the best focus, and then used a sequence of 5 images around.
The results are consistent, and the order of stacking is more important that small focus errors or small camera vibration.
Canon first then Sigma to the left, and Sigma first then Canon to the right. Focus -2 top and Focus +2 bottom.
http://i306.photobucket.com/albums/nn242/Overflate/TC_CS_SC_zpsmjakjfcp.png
|