Re: Hello from Lincoln, UK
I've got a 37mm polarizing filter, but for using ND/grads I have a 37->46mm step up ring and then a 46->58mm step up ring, and then I use Cokin A filters, where you have an adapter and square filter. This works for lenses with up to 62mm filter thread, which means virtually every m4/3 lens that can take filters, except for the new 12-100mm f/4 and the large telephotos.
The problem with ND grads is the entrance pupil of the lens is simply too small for the gradual effect to be noticeable. Well, it is noticeable, but you have to be quite careful when you work with it. While it works OK with the 12-40 f/2.8, which is a rather large lens with a large front element, the small primes with 46mm and 37mm filter threads are really really small. Make sure you get a hard grad filter that changes from dark to clear within a small space.
Olympus E-M1 Mk II
7.5mm f/2.0 - 17mm f/1.2 - 56mm f/1.4 - 9-18mm - 14-150mm II