So today I decided to shoot a few samples with the new FotoDiox ND Throttle Lens Adapter. The version I have mounts a Canon FD Lens to a Micro Four Thirds camera, and in these samples i'm using my Panasonic GH4. If you're familiar with 'Variable ND Filters' here's a few things to keep in mind while watching the video below (make sure you choose 1080 HD settings).
#1: Not once did I ever see the dreaded 'X' cross hatch while performing any of these tests. Even when going to it's extremes. I don't care how expensive your ND filter is, with certain lenses you'll eventually see this phenomenon when placing a Variable ND Filter to the front.
#2: Image quality did not appear to degrade as much as other ND filters when I tested my 200mm F/4 lens (which on GH4 is over 400mm). Even expensive 'Variable ND Filters' have trouble maintaining sharpness when placed in the front of lenses past 200mm.
#3: Stare closely at neutral areas like the 'whites' and 'black' areas. This filter in my eyes did not show a strong Magenta cast as most 'cheap' Variable ND Filters would. If anything maybe there's a bit of green, but nothing I would complain about for such a cheap lens adapter.
Now whether or not you have beef with the FotoDiox company is none of my business, but there's no denying that this adapter does what it claims and I think it does an excellent job for the price. There are certainly benefits to adding a Variable ND filter 'behind a lens' as opposed to the 'front of a lens' and it shows in these examples. Referencing the video above not once did you ever see weird 'cross hatching' as the nd filter rotated between it's extremes. It also maintained a fair amount of sharpness when used with a 200mm F4 lens which again on a GH4 is equivalent to 400mm+ on a full frame.
Below you'll find 'Frame Grabs' from the video, but you can click on any image below for a larger view.
Obviously there are a few pixel-peepers who will nitpick these examples, so here's a bit of advice. If you're the type to complain about trying to get the best quality out of your lenses, then you should not be looking at Variable ND Filters. Instead you should invest in 'Static ND Filters'. A static ND Filter will always provide the best image quality over the most expensive Variable ND filters money can buy.
In summary FotoDiox is offering up a very nice solution for the convenience of using Variable ND Filters combined with a variety of Lens Adapter Mounts all for under $100 dollars. At this time, I can't speak about the quality of using these adapters for Canon EF, Minolta, or Nikon lenses, but i'm personally very very very satisfied with the results I can achieve with my sub $50 dollar Canon FD Lenses.
One of the 'CONS' of course with this type of setup is that it will not allow you to use a 'Focal Reducer' or 'Speed Booster' which might be a hard trade off for some people. So hopefully these short examples are enough reference for concerns such as a questionable loss of sharpness, color shift and or color cast. Once again take a look at the examples, and leave your comments below about whether you think the product delivers to your expectations.