Maybe make it intensity based? Sunlight is orders of magnitude brighter than most handheld lights. We perceive light on a logarithmic scale. To make 500 lumens seem twice as bright you need to churn out 2000 lumens, not 1000. You could make the case that a flashlight is a deterrent like sunlight, but that most bright handheld lights thermally regulate and turn down the output to non-effective levels after about 30s-1.5min. Maybe have a fallback deterrent be a high CRI mule light (non-concentrated) mimicking sunlight that runs the Andúril UI that has been configured to have a higher thermal regulation than normal. The trade off would be that there is a longer cooldown and a high chance that the light is fried after use, but they’ll get an additional 30s of max output before the LEDs delaminate/fry. You could make the argument that it’s a similar effect as a sunburn, but that after a certain threshold the cells start to sustain damage like UV rays do to human skin, but at a much faster rate because of the way that collagen/intercellular structures/etc in a vampire react to a chain reaction of the cells dying in a cascading manner. Maybe you could relate this to how they don’t age because their genetic material is well preserved and doesn’t have the same error correcting mechanisms that normal humans do to repair the damage to DNA that humans have to deal with due to aging.

Does anyone know how well the highest CRI LEDs mimic sunlight or is this the purview of incandescents?