how to keep light out of a flowering chamber

small gro-cab is 45x45x40 cm. gonna expand it to another one of similar size for flowering chamber.
can u guys figure out how to ventilate both chambers in the gro-cab with just one exhaust and one intake? and still keep light out of the 12/12 flowering chamber while the veg chamber has its lights on?
thought of cutting a whole in the wall that separates them and sticking some reflective tubing thru it but that would def leak light into the flowering chamber....

both fans are 4 inch ventilation fans (industrial bathroom style) that are 2500 rpm

Pipe the air through with a couple of black 90 degree pipe elbows to act as a light trap. Alternatively make a small box open on the back and one end then attach it to the wall over the vent holes finally stuff a/c filter material into the remaining open end. Basically just make bends, light doesn't bend.

Thx for the tips, sounds Worth a try

if the fan can work as an inline you could put the fan between the two boxes. sucks from the veg room and blows into the flower room. The fan would trap a good deal of light and any remaining would be caught from some simple bends. also the light in the veg room is probably cooler(as hot air can decrease fan life). just a thought

the above is the simpler solution though, tried and proven

interesting idea karr, yea think i may just bend some reflective tubing through a hole in the "wall" and see how it goes...
camera on a timer to test the darkness...