This report attempts to give a general overview of near infrared photography. After describing two common applications of infrared photography, in forestry and biomedical applications, a scientific approach is constructed to analyze images taken in the near infrared. A controlled experiment was set up, involving controlled light sources, objects, and imaging devices. A model of the intensity of the image was developed, with each component modeled in Matlab. A transfer function was developed for each system, with the unkown being the reflectance of the object. A number of images were then analyzed, and the reflectances of different images were studied. Finally, some digital images and other images of the outdoors were presented and discussed.
The major effects shown in the image were the differences in the source lights and the reflectances of the different object. The transfer functions appeared to be qualitatively accurate, as they agreed well with the images produced. The Halogen light was shown to be dimmer than the Reveal bulb, while the strobe light was the dimmest given its duty cycle. It was shown how the film used reduced the effect of green and yellow visible light (500-600nm) on the exposure. The images also show that violet light (400-470nm) had a significant impact on the exposure, that was eliminated with the use of a filter.
In analysis of the images, a few general effects were noticed. First was the Woods effect, in which plants and trees came out significantly brighter in the near infrared images, meaning they have a high reflectivity in these wavelengths. Second, the bright color of objects such as flowers and fruits that usually bring these objects out in pictures were reduced in the near infrared. An object being brightly colored does not mean that it will reflect near infrared well, as we expected. Also, it was shown that the metallic components of the circuit board all reflected near infrared light well, regardless of their specific composition or coating. Finally, it was shown that the bruises on the fruits came out brightly in the near infrared images, and the possible use of near infrared photography to search for bruised fruit is an intriguing possibility that could be researched further.
Finally, we hope this project will serve as a solid foundation for future projects on near infrared photography. In future years of this class, we hope that other students will continue looking into this area. Projects focusing on one type of specific application of near infrared photography would be able to go into greater depth on an issue. Also, the ability of some digital cameras to take near infrared images should be explored more, and a comprehensive model developed. We recommend that students take an interest in this type of project, as some of the results were quite stunning, and we enjoyed working on this project immensely. Neither of us had performed much photography previous to this project, but this project has certainly interested me in the hobby. We hope you enjoyed the report!
Home Introduction Applications Methodology Modeling Results Conclusion References Appendix I Appendix II