> That's an f 2105, about 14 stops larger then f16. 14 stops is 16384 > times exposure. If you needed 1 second at f 16 you would need to expose > for about 4.5 hours at f 2105. Hope you have a good tripod for that tube.
But if he's using 400 ASA film, that's only 40 sec as the BDE exposure, excluding reciprocity.