Main difference between III and IV is that the IV version is padded inside to avoid internal reflection which some described to be an issue with some lenses. Other than this, it has the same functionality as the III adapter.
The Metabones Smart Adapter II is only good for cropped sensors in the Sony NEX cameras.
Actually they opened the throat on the 4 also so Canon shift lenses work better
Here
EF-E Smart Adapter (MARK IV) - Metabones®
www.metabones.com/products/details/MB-EF-E-BM4
The new design of inner housing in MARK IV has a bigger inner hole. Improving the Tilt shift lens preformance. The inner hole is painted with matt coating.
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Interesting. Thanks for pointing that out. I hadn't realized that they were producing a flocked Mark IV. Has anyone compared the 2 Mark IV's with a canon tilt shift lens?
suchy wrote:
Interesting. Thanks for pointing that out. I hadn't realized that they were producing a flocked Mark IV. Has anyone compared the 2 Mark IV's with a canon tilt shift lens?
It appears the latest one performs the best as there are less reflections.