For those using conventional radiographic methods there are several options to digitise film images. The simplest and cheapest is to use a digital camera with a high resolution. For high definition dental films the minimum satisfactory resolutions are 1200 x 800 for periapical films and, 2400 x 1600 for occlusal films. Larger conventional screen-film images should be photographed at as high a resolution as possible, however, the lower film resolution of screen film means that 3000 x 2000 is often more than sufficient for most purposes. If the images are to be sent by e-mail they should be cropped to the relevant areas and saved as high quality Jpegs. If images are being sent on CD rom then Tiff format is preferable and the whole image can be sent.
To get the best possible images:
- Use a tripod or other support for the camera
- Place the film flat on a good quality film viewer
- Blank around the film to exclude unnecessary light
- Only transmitted light is wanted to form the digital image, so-
- Turn off the camera's flash and
- Darken the room to eliminate all reflections from the film
- Position as far from the film as possible filling the frame with the image
- Use aperture priority with an f stop setting of around f 5.6
- Pre-focus the camera if possible rather than relying on autofocus
- Take multiple exposures bracketing the exposure by +2 and -2 lf stops
The narrow contrast range of many radiographs makes photographing them difficult. This is where the bracketed exposures can help, different parts of the radiograph being recorded by different exposures.