- Determining brace locations in existing instruments -
This works best in a totally dark room. Set up your shot for a long exposure (1 second or more). Get everything in position. If you don't have a tripod for the camera, get a friend to hold the strobe for you. Turn the lights off, release the shutter, fire the strobe. Depending on your position, results may vary. I got the best results shooting the strobe through one of the small holes. The closer to the face the strobe is held the better the reults.
Stud finder method:
This method is less precise, but if you locate from both sides, and split the difference, you should be able get a fairly accurate location. Of course this won't tell you the shape and dimension of the brace, just it's location, and assuming its straight across the face. Locating on both treble and bass sides of the face should reveal any brace non-parralelism.
On ouds without roses, (such as this 1920 Adbo Nahat, owned by Michael Cone, and taken during restoration procedures) one can place a bright light (made by wiring a single bulb receptable to a switched cord) inside the oud and take a picture in a dark room. Set the camera for a long exposure and experiment for best results. Caution: One must use a fluorescent bulb instead of incandescent or halogen to prevent excessive heat inside the instrument. Multiple-LED flashlights would also be an option.
Tuning fork method:
Strike a tuning fork and gently move the handle end along the face. When it's over a brace, the tone with change revealing the position of the brace.