This is the 4.5" Round Combination Infrared 85 Neutral Density 1.8 (ND) Filter from Tiffen. What do you do when you must take some photos outdoors and all you have left is tungsten film? Using tungsten film in daylight will produce a bluish cast in the photograph. The 85 series of filters will "bring back", i.e. color balance the tones in your images. This yellow filter is used to correct differences in color temperature between the recording medium (film/video) and the light source.
Color shift is a critical factor in digital photography especially when dealing with the infrared spectrum - and even more important when shooting with HD technology. Unlike traditional film cameras, CCD or CMOS sensors of a digital camera are, by nature, susceptible to infrared contamination. Manufacturers try to avoid this problem by incorporating an infrared absorbing filter on top of the image sensor. Because these filters do not have a sharp cutoff at the infrared wavelengths there has to be a compromise in order not to exclude visible red wavelengths. Despite these precautions, some infrared wavelengths pass through resulting in contamination of the image. This filter delivers the best of both worlds - color balance as well as minimizing infrared contamination.
A neutral density filter has several uses and offers the possibility to achieve otherwise unachievable results. It enables the shooter to adjust exposure without affecting color balance. An ND filter appears gray and reduces the amount of light reaching either the sensor of a digital camera or the film plane of a traditional film camera.
Neutral density filters are used to create some unusual special effects such as capturing the "blur" of the rippling water of a waterfall or the swirling effect of city traffic. Since it allows the use of slower shutter speeds in bright light, it becomes possible to create these special effects that would normally not be possible to capture without the filter. And, since it can also help to control your depth of field, it permits you to shoot at wider apertures. Ultimately, its value is in helping to prevent bright, overly washed out images shot in bright light.
A 1.8 (6 stop) Neutral Density filter requires one additional stop of compensation from the 1.5 variety. If your subject is walking through the scene, it is quite possible he may not even show up since your shutter speed will be so slow that there may not be time for the recording medium to catch his passing.
Water White glass, using Tiffen’s ColorCore technology, is characterized by a high transmission quality. Typically, it will transmit 98-99% of the light. It also features an anti-glare and anti-reflective quality that makes it useful in a wide range of uses including the movie theater industry, store and art displays. The glass is virtually defect-free and is becoming more and more prevalent in digital equipment.