A factor that a lot of ND filters do not take into account is the affect of IR (Infrared) light on color. As digital imaging sensors become more and more sensitive to light they are also more susceptible to overexposure and more sensitive to infrared light. To address these two sensor issues Hoya developed the SOLAS line of IRND filters. This reduces the amount of light entering the camera allowing for either very wide apertures or very long shutter speeds being used in bright lighting conditions. Normal ND filters often have a transmission spike in the near infrared (A.K.A High Red) area of the color spectrum that leads to color casting. The Hoya SOLAS IRND filters are designed to evenly suppress IR across red, near-IR and IR areas of the spectrum to avoid any spectrum spikes that can add a color cast to the image. The combination of IR suppression and exacting color balance through use of the latest ND materials means the SOLAS series maintains neutral color balance that is matched in every density throughout range.