A split neutral density filter aka graduate neutral density filter is a useful tool in the field to overcome strong contrast between a dark foreground and a bright background. Part of the photo filter is grayed out while the other part is clear. It thereby allows less light passing through the lens onto the sensor for that gray filter area and therefore helps better balancing the image. I regularly use the ND filter for Landscape Photography and sometimes for my cityscape photographs as I am always striving for best possible images in the field, keeping post processing to a minimum. A practical example to demonstrate its function and impact is shown in above Boston Skyline Photography picture where I hand-held the filter to the left of the image while leaving the right side unfiltered. Thanks to the ND photo filter we are able to meter on the yachts in the foreground, lock the exposure and after sliding the filter into position correctly expose the sun-lit Boston skyline and orange clouds. Houses, shoreline and sport boats in the shade remain visible in great detail because the exposure was based on metering for the darker foreground. As we evaluate the area without the filter to the right, the sky is overexposed and washed out, making it a dull and boring image. In fact this part of the image does not even reflect what I actually experienced at the time of capturing the picture. The ND filter is a great tool to carry in your camera bag and enables us to overcome those strong contrasts we are often challenged with in the field.