Lee's Big Stopper neutral density filter will block out about ten stops of light for daytime long exposure photography. Since the Big Stopper is used in a holder instead of as a screw-on, filters can also be stacked for even more light reduction. The holder is well-designed, with foam padding to help prevent light leaks, a common problem in long exposure photography. Image quality is quite solid as well, with no reduction in sharpness.
While the Lee Big Stopper gets solid images, there is a noticeable green color cast when using this feature. That's a common problem with ND filters, but it's a little more pronounced than similarly-priced filters here. The tint is an easy correction in post-processing, but certainly worth being aware of nonetheless. And while the holder filter systems are very versatile, they are also bulky and take up more space in your camera bag compared to the screw-in type. When you factor in the cost of the filter, the Lee Big Stopper is on the pricey side. For a little less light reduction, consider the similar Little Stopper.