Strangely, it's not enormous at all. It's infinitesimally small.
What I'm having a hard time wrapping my wee noggin around is the idea of using light to see light moving at the speed of light, and/or seeing light disappear.
An optical photo requires light to shine on the object being photographed, be reflected off that object, and then move from that object back to the camera. If light moving at light speed is your object to be photographed and is located at point A., and you are trying to capture light reflected off that object in a camera at point B., there is distance that must need be covered by light between point A. and B. Assuming that the light being photographed and the light being used to illuminate and capture the image are moving at the same speed (to wit, the speed of light), that seems problematic, or at least extremely Heisenbergian or Schrödinger-esque.
Other end of the spectrum... how do you reflect light off an object that sucks all light, indeed all EM waves of any length?? Again, rather problematic... at least in my limited, three-dimensionally-hobbled cranium.
All that said, there are strange things done in the midnight sun. An acquaintance of mine runs a company that optically inspects chips to a resolution shorter than the wavelength of light. Huh?? He explained some of the PFM behind how that's possible. It kinda sorta makes sense, but still feels like PFM. Big organizations with three letter monikers are paying him scads of lucre... so, like F35s, it must work good and last a long time.