The Hitech 105mm Multistop and Warm2Cool Filter Kit contains both the Multistop variable neutral density filter and the Warm2Cool variable color filter. These two filters have the ability to compensate for a larger number of filters and allow you to reduce the number filters you carry.
The Multistop filter is a solid variable neutral density filter providing a reduction of about 1 to 6 stops of exposure. The 0.3 to 1.8 density creates a darkening of the entire image, allowing you to photograph with a wider aperture or slower shutter speed than normally required. The degree of density is easily controlled by rotating the front filter ring, allowing you to previsualize the additional exposure length required. By slowing your exposure time or increasing your aperture, you are able to control depth of field and convey movement more easily. Neutral density filters do not affect the coloration of the image.
The Warm2Cool filter is a variable color enhancement filter providing a diversity of color possibilities from cooling blues to warming yellows. You can easily manipulate the effect of the filter by rotating the front filter ring in order to browse through the fluent range of tones. This eliminates the necessity to carry multiple color correction filters or to be dependent on one type of colored filter.
Both filters feature a large front rotating element to help reduce vignetting when used with wide angle lenses. They are constructed from specially formulated CR-39 resin sandwiched between two layers of high-quality Schott glass and have aluminum filter rings.