"I too have an EF 100-400 IS as well and have considered the same thing. I have owned the 5T/6T in the past and they are quality macro glass but at 67mm, stepping down from the 100-400,s 77mm is quite a jump. My guess is that some vignetting would occur."
1: Nikon's 5T/6T closeup filters are 62mm not 67mm.
2: Vignetting does not occur when step-down rings are used on telephoto lenses. The affect is more akin to stopping down the lens, the step-down ring acts like a smaller aperture. Vignetting only occurs if the smaller aperture is some distance in front of the lens.
You will loose about one stop when using a 77-62mm step down ring.
Using the 5T/6T will give good results, although the viewfinder may be a little dark, and focusing may be harder as a result. Greater than life size will be obtained with the 6T.
Macro photography with Canon 500D close-up filter
in Nature
Posted
"I too have an EF 100-400 IS as well and have considered the same thing. I have owned the 5T/6T in the past and they are quality macro glass but at 67mm, stepping down from the 100-400,s 77mm is quite a jump. My guess is that some vignetting would occur."
1: Nikon's 5T/6T closeup filters are 62mm not 67mm.
2: Vignetting does not occur when step-down rings are used on telephoto lenses. The affect is more akin to stopping down the lens, the step-down ring acts like a smaller aperture. Vignetting only occurs if the smaller aperture is some distance in front of the lens.
You will loose about one stop when using a 77-62mm step down ring.
Using the 5T/6T will give good results, although the viewfinder may be a little dark, and focusing may be harder as a result. Greater than life size will be obtained with the 6T.