Modern LED information signs have become commo place on many passenger railroads as means of identifying trains.
The challenge for photographers is capturing the messages displayed by these signs.
Many LED do not produce continous light output and pulse or flicker. To the human eye the light souce seems continuous, but when photograhing at comparatively fast shutter speeds some or all of the LEDs are between pulses and appear dark in the photograph.
Where banks of LEDs are employed these may appear in images as meaningless arrangements of spots, or missing significant portions of the intended message.
One way to capture the lights is to work with a comparatively slow shutter speed, usually 1/60th of a second or less. The difficulty is that to stop a moving train, it is normally recommended to work with faster shutter speeds (often 1/250th of a second or faster).
Another consideration is the relatively low amount of light produced by LED that full daylight these often appear dim. Photographing LED signs in low light, on an overcast day or at dawn, dusk, or evening, allows the lights to appear brighter relative to ambient lighting conditions.
On a visit to Norfolk, Massachusetts with Kris in November, I made this sequence of images of MBTA Train 2706 at various shutter speeds to show how the lights in the sign appears at 1/640th, 1/250th, and 1/60th of a second.
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