To achieve a flickering lights effect for scenes in their film "Indelible", the filmmakers used both the internal location lighting and a free flashlight app from the App Store that has strobe lighting effects. They discovered the internal lighting alone did not provide the desired effect, so they alternated two phones running the app at different speeds between 6-8 to make the flickering look natural rather than staged.

1. In our film “Indelible” we have a few
scenes where the lights are flickering; to
achieve the flickering lights effect we
used this app in addition to the internal
lighting at our location. This is a free app
available to download from the App
store; it’s a flashlight app that has strobe
lighting effects.
We chose to usean additional app as we
discovered that the internal lighting
didn’t give us the effect we desired.
We wanted our flickering lights to look
natural and not staged; hence we had the
flickering going at a relatively fast pace. As
you can see in the image you can adjustthe
speed from1 – 10 depending on how strong
you want the strobeto be. We alternated
between 6 and 8 to see which gave us a
better effect. In the end we used two
phones with the app installed and had both
on different speeds, one at 6 and one at 8.
We didn’t justuse the app alone as it was
not strong enough but it did provide
additional effects hence why westill used it.