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 www.sbig.com/sbwhtmls/IRfilterchart.htm (looks like a KG5). See www.lifepixel.com/ir-tutorials/canon-20d-digi 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: www.k3pgp.org/ccd/filter/hotmirror0.gif
echeng.com/photo/infrared/filter-data.html Red and IR Wratten filters
Main plot at: http://www.flickr.com/photos/edhiker/3023085085
key words: IR eye response light silicon camera infrared 50DH edhiker