Should I get this or baby death?
(opteka) baby deaths are generally wider, but the price might be out of league. So if there's no budget boundaries, then I'd get either
1) 43mm babydeath, 37-to-43mm step-up ring, maybe a few 43mm spacers;
2) just the 37mm babydeath lens;
3)
Martin Rowlands' Amazon link actually looks promising. Never heard of that brand though.
4) kenko .43x, if you're on low budget.
Why did I just suggest #1 with step-up rings and spacers? Since the glass size is the same, the lense's aperture on this is bigger, thus using with step-up rings and spacers you might actually achieve a wider picture because there would be less vig for the same size of the glass, cause on a 37mm model there's more material used in order to generate a 37mm diameter threaded end. If that made any sense...?