Thursday, November 13, 2008

Eye vs Digital Camera - Hot mirrors, KG3, KG5 filters

We see red better during the day. Your camera has a filter that mostly blocks wavelengths longer than about 650nm (deep red).

Most cameras now are using hot mirrors, multi-layer interference coatings that give a sharper cutoff. KG5 glass was used more in the past, note date on (looks like a KG5). See tal-infrared... for how easy a camera can be converted to take IR pictures. My nephew just bought a Canon 50DH from Hutech (clear glass instead of cut filter). Great camera! Why Canon doesn't offer such a camera themselves for the scientific community and hobbyists is a real mystery.
Below are some curves for filters used to modify the camera's response to the longer wavelengths that silicon is most sensitive to:
Most likely a "hot mirror", typ curve at: BG18 BG38 KG1 KG3 KG5 Red and IR Wratten filters

Main plot at:

key words: IR eye response light silicon camera infrared 50DH edhiker