The information that got me started was discussing someone having written on a picture in pencil and how the pencil had faded over time. They wanted to raise the old pencil to see what it said and then remove it from the finished image. As I recall, someone talked about using IR on the original to bring out the pencil and make it legible. But several others were discussing using it on tin types and daguerreotypes to bring out faded or hidden information. I've tried googling for the original thread but haven't found anything.
Does anyone here have knowledge on how IR could be used to restore an old photo?
Re: Infrared Scanning
Not with regard to basic restoration. As you mentioned, it is used to remove dust from transparent media such as slides. Many of the newer scanners have this capability and us it in conjunction with ICE when scanning transparent media. It is not available for opaque media when used with scanners. The IR/ICE process does two passes. One without IR, one with. Since the pass without will not penetrate the dust particles, and the IR does, the difference can be assumed to be dust and eliminated.
Many different light sources are used by conservators to evaluate the properties of images. It simply depends on what you are trying to achieve. Raking light is useful for evaluating surface distortions, UV for evaluating coatings, etc. But, to have a single light source reveal all that is needed for a restoration may be a bit overly optimistic. I would think it may take several. And, then you would need camera equipment sensitive to that light source. There may be some information revealed by IR (since that was your question), but it was deemed not very useful by the industry. (That is why they opted not to build it into the scanners.)
You could certainly experiment on your own. There are plenty of IR illuminators on the market very cheap, most related to the security industry. And, most digital camera sensors are sensitive to IR light. Plus, there are plenty of IR filters available for the cameras. So, it would not be too hard to do.
If you come up with something on that link, please post.
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