Comments about Cokin Cokin Coupling Ring P with Filter Holder:

This coupler will only work if you are using the standard three-slot holder already attached to your lens, which means by the time you put another holder on the front of the adapter you will have a serious vignetting problem when shooting wide angle shots (even when using the wideangle holder on the front). Using my 12-24 on my Nikon D90 I can get corner vignetting even at 22mm if the wideangle holder used on the adapter is rotated to the right angle. When the wideangle holder is kept level I can shoot down to 20mm before the circular adapter opening starts to cut the corners. I would assume this means the same thing would happen on full frame cameras as narrow as 30mm (1.5x crop), but in reality this would differ from lens to lens based on the geometry and construction of the filter thread in relation to the lens optics. This adapter can be useful to have two filters used at different angles at the same time, just not on very wide angle shots. Reccomend as long as the restrictions of its design are considered before purchase.