Seeing through a veil of Neutral Density!

Using neutral density filters has become very popular recently, so much so that Lee has had a very difficult time keeping up with the demand for its “Big Stopper”, which produces a whopping 10 stops of density. It turns out that it is not so easy to make the Big Stopper, or at least make it neutral and keep the density even, corner to corner over a 4” area. Due to these high tolerances, Lee can only produce a limited number of the filters per month. There are several uses for this filter. The first one is to simply blur anything moving during a long exposure, such as water or clouds. The second one, is a bit more subtle and I believe is the interesting part of the effect, it lowers the contrast of a scene. In addition, I like to stack a polarizer on top of the Big Stopper for yet a different effect.

This begs the question, "what really happens when you place that ND filter in front of your lens?".  And again what is happening with the polarizer on top of the ND? Typically the ND filter appears to lower contrast and the polarizing filter increases contrast. Here is a sample of 4 images taken with no filters, polarizer filter, Big Stopper, and the Big Stopper with polarizer.

This is a screen grab of the 4 images all with a white balance set in the exact same location within each image. No other edits were made. The ND filter does not actually lower the contrast of still objects but rather decreases the amount of specular highlights when they move through the scene during the long timed exposure. For example, a Big Stopper filter will not lower the contrast of a parked car with a shiny bumper reflecting specular highlights. But a stream with moving water bouncing hundreds if not thousands of tiny specular highlights over the duration of the exposure will change dramatically. This is due to the fact that the moving specular highlights are not lit long enough during the long exposure to become an actual specular in the image captured. Thus, they are invisible and with no specular highlights the scene contrast ratio is lowered.

In addition, if you stack a polarizing filter on top of the ND, which typically blocks bounce light reflecting from shiny surfaces, especially water, the net effect is dramatically diffused light. It is this diffused look that you must consider while shooting with the ND and/or polarizing filters.
In most scenes a polarizing filter will slightly increase the contrast of a image. This is due to its effect of cutting haze and blocking bounce light, thus making colors more saturated.

Notice the difference of the dry to wet sand on the beach and the windows in the shady side of the building. These areas as well as other contain more contrast in the image with the polarizing filter.

I hope this helps you decide when and when not to use these filters. 

Tip -  If you’re attempting to compose your image with live view on a Nikon D800, don’t forget to open the aperture up all the way and increase the ISO. These two alterations will allow the camera to become sensitive enough and allow you to utilize live view for composing. Canon shooters need not alter either as the live view settings typically do not preview with the aperture stopped down.

Iceland, no filter:

Iceland, with Neutral Density + Polarizing filters: 

Final Image, processed in Lightroom

Life is short, take pictures!

- Marc