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<p>[QUOTE=&quot;-jeffB, post: 3985529, member: 27832&quot;]You aren&#039;t the first to say this, and others have insisted that only halogen (incandescent) bulbs are acceptable when examining a coin to <i>grade</i> it.</p><p><br /></p><p>I have a feeling that it&#039;s less about <i>spectrum</i> and more about <i>size</i>. An unfrosted incandescent bulb (without a reflector) emits light from a very small area; a fluorescent lamp, or a frosted bulb of any kind close to the coin, emits light from a larger area.</p><p><br /></p><p>A point source (small area) is best for highlighting luster, hairlines, and rub. A wide or diffused source will make it harder to see all of these. That alone would make fluorescent a bad choice.</p><p><br /></p><p>Spectrum: an incandescent bulb has a very smooth spectrum, although it&#039;s usually weighted toward the red and away from blue. Fluorescent bulbs have irregular spectra, with several strong lines (spikes). LED bulbs tend to have a large spike in the blue spectrum, and a broad hump from red through green.</p><p><br /></p><p>I&#039;d expect this to make a difference when you&#039;re trying to capture toning. For everything else, though, color just isn&#039;t that significant, and I&#039;m not sure why it would matter what spectrum you&#039;re using. You want to see luster, hits, damage, and wear, and all of those behave the same no matter what color you&#039;re using.</p><p><br /></p><p>One last thing for photography: <b>flicker</b>. Old four-foot fluorescent tubes (office lighting) tend to flicker 60 or 120 times per second in the US, 50 or 100 times per second in UK. Compact fluorescent bulbs flicker faster, but still flicker, and might have the 50/60-hz cycle superimposed on that. Incandescent bulbs in general don&#039;t flicker enough to notice. LED bulbs -- some do, some don&#039;t.</p><p><br /></p><p>This is important to cameras, though, because if you&#039;re using a short exposure, it might happen to fall while the light source is unusually dim or bright. (My latest camera actually warns me if it thinks my lighting is flickering). That&#039;s an argument in favor of incandescent lights. I&#039;m still hoping to make it work with LED sources, though; I hate the heat of incandescents, and I doubt that coins like it much either.[/QUOTE]</p><p><br /></p>

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