Upload & Sell: On
I just got my Lee adapter for the 17mm f4 L TS-E lens, and it looks very functional. The construction is all metal, and the strength and durability appear excellent. The adapter bayonets on to the lens similar to how the cap would, but has no locking detent to keep it on. But the friction of it bayoneting on is high, and it would require a large amount of rotation before it would become loose. The only negative about the bayonet action is that it seems almost too tight, but I expect I will get used to it.
The front face of this adapter projects forward to just in front of the front lens element, probably less than 0.3 mm. When you put a Lee filter holder assembly on the adapter, the rear slot is located such that the back face of the 4 inch wide filter is going to be about 0.5 mm in front of the front element, so they have is about as close to the lens as you would ever desire.
The hole in the front of the adapter is about 84.6 mm in diameter, which is slightly larger than the inside of a standard Lee wide angle adapter if you remove the inner ring, like is described for making the do it your self lens cap adapter. . In addition, the front inside rim is beveled at 45 degrees for about a 2 mm width, which additionally helps for field of view through the adapter. It looks like they have done this about as wide as you can imagine and still use a normal Lee filter holder for 4 inch filters, which needs to lock on to a standardized bevel edge, and thus can not be larger.
I am very happy with the unit so far, but have not done any field of view checking. But any previous testing with 4 inch filters in a Lee holder will end up pretty much the same as using those items with this adapter, so I expect limited shift coverage, but full tilt coverage. Don't expect any magic out of this compared to other 4 inch Lee holder solutions, like with the lens cap adapter.
I do have a filter holder set up for one filter slot plus the 105mm threads for a polarizer, and will check that out for if a polarizer shows up in the corners with no shift. I will also set up a Lee holder with just the 105mm threads on it, with no holder slot, and see how that works.