Murder in Black and White

Generally I am off murder shows, even old time radio ones although there are exceptions.  I was listening to this one:

https://www.oldtimeradiodownloads.com/crime/casey-crime-photographer/murder-in-black-and-white-1948-03-18

One thing that stood out was the phrase: black light.  Since the 1960s this probably refers more to ultraviolet light for posters but in this case the reference was to infrared, IR.  In the olden days Kodak and others sold special infrared film.  I remember one time I tried it and the leaves on the trees came out white rather than dark as was usually the case with black and white.  Manual focus cameras also often had a red dot on the focus dial.  To take an IR photo you'd focus the camera and then move the focus ring to the red dot since IR focuses in a different plane than visible light.

But you could also buy flash bulbs for infrared.    In the Casey show the plot hinges on the fact that a photographer taking an IR flash photo at night might not be noticed by the subject of the picture.  The GE 5R is mentioned here:

https://www.bhphotovideo.com/explora/photography/features/exploring-the-world-of-infrared-flash-photography

here is a picture of 5R bulbs from an Ebay listing:

probably the same as regular flash bulbs except for that wacky coaating

source: https://www.ebay.com/itm/297817466942

I suppose that now people use something like a Gopro with IR LEDs for taking videos of people at night without their knowledge.  Cheap cell phone cameras are sensitive to IR:

https://wb9kzy.blogspot.com/2022/02/sometimes-old-tricks-fail.html

But I suspect that even high output IR LEDs aren't useful unless you use a bunch of them.  Still, it might be a fun project to try ?  It certainly would be a LOT cheaper than special IR film and $10 a shot flash bulbs !  There are also filters sold on Ebay for high powered LED flashlights which might also work in this application.  

"what was that ?"

"I dunno - looked like a dim red glow"

Smile, you're on Candid Night Camera !

Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm