Yesterday, 13 October 2018, I exposed these views of an LED (light emitting diode) signal on Irish Rail at Limerick Junction.
Take a careful look at the yellow aspects in the respective images.
In the top photo, the yellow LEDs appear relatively dim (and much dimmer than they seemed in person). On the bottom photo these are brighter.
Many LEDs do not produce constant light output and flicker many times a second. Although you cannot see this with your naked eye and the light output appears constant, in fact the light is blinking. When you use a fast shutter speed the camera only captures a portion of the light emitted and so the signal lights seem too dim.
The key when photographing LED signals is to use a relatively low shutter speed. In this case 1/60thof second is much better than 1/400th.
Another tip when making effective LED signal photos is to make the most of subdued lighting which can make the signals seem brighter than the light around them.
sAT. oCT. 13 i WAS AT iLLINOIS rAILWAY mUSEUM AND was very impressed at the great variety of older signal equipment in use when I rode the streetcars and interurbans.
IF you redo your signal book, you may want to go to IRM for photos or similar info, next time you are in the Midwest.
Jim Egan, Eau Claire, Wi.
Thanks ! Very en-lite-ening.
Hi Brian – If the dc power for the LEDs is filtered properly, they will burn steady. Just using a simple bridge rectifier alone allows the ac ripple to become dc ripple…… I noticed this in 1976 when I converted my o scale model PRR PLs to LEDs, and then added a capacitor to the lamp power supply to smooth out the ripple effect. The ATK reworked PCLs and many highway applications seem to have less ripple… Bill.