I want to add this info to my last post. I was waiting to receive permission to forward this info to the group from the author. It comes from Mike Collette of Betterlight scanbacks. Subject: Re: [Better Light] Betterlight IR settings Do all of you realize that your Better Light (and Dicomed) scan backs can be used to capture near-infrared images, in either monochrome or "color"? Just remove the infrared-blocking filter, and all three color channels become VERY sensitive to near-infrared energy -- between 700 and 950 nanometers -- with a baseline (lowest) sensitivity rating equivalent to about ISO 800 (vs. ISO 100 for standard color captures). Each color channel also still responds to its particular color of visible light (red, green, or blue), and I have seen some very interesting images made using this technique. For strictly monochrome images, select a single-channel capture (I would suggest using the RED channel, which has the greatest infrared response), and don't worry about the color balance setting, since there won't be any color. The Neutral number for the chosen capture channel will still affect the sensitivity of that channel, as always, and the other two channels won't be used. For convenience, you might want to set the Neutral numbers to be the same for all three colors, so you can run the ISO up and down over its entire range without limitations. You can choose whether to allow any visible light along with the infrared by using a visible-blocking filter such as the #87 or #88A Kodak Wratten filters to eliminate any visible light, or no filter at all, to allow all visible and infrared energy into the camera. For potentially interesting "color" infrared images, you probably will want to neutralize the scan back for your chosen illumination, so objects reflecting primarily infrared will show up in monochrome, and objects reflecting primarily visible (colors) will show up in muted (low saturation) colors. This is what I did years ago to come up with the "preset" color balance for infrared captures in the old Better Light software for Dicomed scan backs. The procedure is the same as any other color balance, except that you can't always be certain that your "neutral" target (gray card) remains neutral into the near-infrared spectrum. Choose a pigmented gray reference, like the Macbeth chart(s), or just use some nearby (colorless) concrete, which seemed to work pretty well for me. The neutral reference must be illuminated by the same source that you will be capturing with, so you get the same "mix" of visible and infrared energy (same source "color"). Include the neutral reference in your prescan, and make sure the reference is not over- or under-exposed. As usual, just click the spotmeter in the neutral object, and then click "Auto-Balance" to have the software re-calculate the necessary Neutral numbers; the interactive display of our new ViewFinder software shows you the results right away, so you can judge how "neutral" everything looks. Once you've found a set of Neutral numbers that you like for a particular illuminant, you can save them in the Color pop-up menu as a New Setting, with an appropriate name. Images captured using the infrared capabilities of the scan back will almost always have LOWER CONTRAST than their visible-light equivalents, so you may want to make some adjustments to the Tone curves used to capture these images. Infrared light also focuses at a different position than visible light, and very few lenses will focus both visible and infrared to a common plane, so you may want to try the digital focus verification in our software to assist with focusing the image you cannot see... Even when using focus verification, infrared images may not appear as sharp as visible-only images, because the longer infrared wavelengths penetrate deeper into the silicon of the CCD, and tend to produce a response in several nearby pixels as well as in the pixel originally "hit" by an infrared photon (in other words, the CCD has a lower modulation transfer function for infrared light). > > Here are some links, I hope you find them useful. > > http://www.a1.nl/phomepag/markerink/mainpage.htm > they have some digital infrared links. > > http://www.echeng.com/photo/infrared/ > > http://www.lesjorgensen.com/ > > regards, > > Roderick > > >> >> Here are a couple of early articles on the topic ... >> >> http://www.rit.edu/~andpph/text-agfa-1280-ir.html >> http://www.rit.edu/~andpph/text-ir-examples.html >> >> or http://www.rit.edu/~andpph/text-infrared-ultraviolet.html >> and another one >> >> http://www.echeng.com/photo/infrared/ >> >> regards, >> >> Andy >> >
