The 4.5" Round Hot Mirror IR Neutral Density (ND) 0.9 Filter from Tiffen deals with color shift that is a critical factor in digital photography. This color shift is directly affected by the infrared spectrum. Specifically, in high definition photography, the sensitivity of imaging sensors to IR has become a challenge. This is particularly evident when using standard neutral density filters that absorb visible light but pass infrared.
Unlike many photographic films, the CCD or CMOS of a digital camera is inherently susceptible to infrared contamination, even when the manufacturer attempts to reduce this problem by adding 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. This results in some infrared wavelengths being allowed to pass.
While minor infrared contamination does not normally cause much of a problem for visible images, when using conventional neutral density filters especially denser grades, this issue is multiplied by the filter factor. Tiffen has now addressed this problem with the introduction of its exclusive line of their Infrared Hot Mirror filters. Hot Mirror filters completely block infrared throughout the entire spectrum.
A 0.9 (3 stop) Neutral Density filter starts to show significant blur in the shot. By now, you can create some real movement in city traffic or really isolate your subject from the background since you will be shooting with a much wider aperture.
Tiffen's ColorCore glass is produced through a process that entails permanently laminating the filter material in between two pieces of optical glass that are ground flat to tolerances of a ten-thousandth of an inch, then mounting them in precision aluminum rings.