Hi Pedro,
This is a few years late, but may help the next reader. . . In the book, "Adventures with Pinhole and homemade cameras," they have the very image of Justin's you posted and they give the specifications as: Exposure in ambient room lighting was 15 minutes at f/186 on 4 x 5in iso 100 black and white film. He filled the beer can with water so it sank to the bottom of his bathtub (and filled the duck with sand). hope this helps!

Quote Originally Posted by 314ter View Post
You'll have to wait till March, when I come back from my hollydays, to see my under-the-sea photos. But I'll show you my sink attemps soon! (I'll begin as soon as I finish with my exams and as soon as I finish the camera).
Thanks you all for the support!!


PS: You can see one of my Pinhole Photos here