Renfield: No, no, master. I wasn't going to say anything, I told them nothing. I am loyal to you master.
In the scene where Renfield enters Dracula's castle, it is past midnight and on the outside, it is dark. But there is a LOT of bright light streaming through the windows into the castle, throwing well-defined shadows.
To accommodate all sorts of viewers, the studio also made a silent version of the film (for cinemas without sound equipment) and a Spanish-speaking version (to be shown in Latin America). The Spanish version is considered a better film, because it was filmed after the English takes each day, so the Spanish director and actors would watch the English takes and decide how to improve on them.