Hot Mirror applications for use with digital photography
Digital photographers use many filters to achieve varied effects or solve problems, such as using a hot mirror filter to reduce the effect of the near IR on visible light images. One particularly telling issue is taking images of people with a digital SLR. There are several other issues related to near IR bleed, but the most noticeable coloration differences are really the biggest reasons to use a hot mirror filter.
One issue noted by photographers is how infrared radiation can penetrate skin layers a bit deeper than visible light, and then will pick up a blotchy discoloration that the camera interprets in the visible spectrum. The IR radiation can also pick up sub-dermal features such as veins. This particular effect can lead to the need to edit images with software designed for that purpose, but can be quite time consuming. Adjusting these images with software can also lend toward an airbrushed look that is sometimes less than desirable.
Another issue that can be quite cumbersome is how artificial light sometimes gives imagery a greenish tint. This can cause otherwise good pictures to lose their color neutral tone. This is especially noticeable when dealing with white or near white backgrounds within indoor settings. Staged indoor environments like motion film lots or live theater are good examples of situations where a photographer or filmographer might want to reduce the amount of color variance due to infrared bleed.
Essentially solutions for this problem break down into two types, post capture and inline. Post capture solutions, such as software used to “color correct” images are time consuming and often less perfect than desired. These solutions also tend to lead to other problems where desired hues are lost or adjusted in negative ways, such as lips turning paler to match skin color, or eyes turning from hazel to blue while trying to correct for greenish tint. Inline solutions range between high end digital cameras that auto-correct for color variance due to near IR bleed, or lenses that adjust for the color variance. Some of these solutions are better than others, and as technology improves and high end cameras become better at correcting for things like this it becomes less of an issue. Ultimately, preventing the near IR from ever affecting the image in the first place is ideal. This reduces the amount of time and technology needed to prevent this problem. In order to do that you would use a hot mirror filter that blocks the near IR from entering the camera.
ZC&R creates hot mirror filters for just this purpose. Please email us or call 800.426.2864 for more information.
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This entry was posted by ZC&R, on Wednesday, March 4th, 2009 at 5:00 am and is filed under Hot Mirror, Optical Applications. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response below.