Panoramic PC-1000, Service Manual

Page: 46 / 94

Appendix
© Copyright 2008 Panoramic Corporation
Darkroom Procedures
Darkroom Light Leak Test
Extraoral fi lm is more sensitive to light than intraoral fi lm. The purpose of the intensifying screens inside
of the cassette sleeve is to convert the X-ray energy into light, thus exposing the fi lm. While the light
sensitivity of the fi lm allows a very small amount of radiation to expose the fi lm, it also can pose a problem
if the darkroom is not completely lighttight. Small light leaks can cause fogging of the fi lm while handling
and processing the fi lm in the darkroom.
The following test should be performed in the darkroom under safelight conditions to ensure it is lighttight:
1. Remove one sheet of extraoral fi lm from the box.
2. Lay it on the counter in the darkroom under normal darkroom conditions.
3. Place a couple of coins, a pair of scissors, or any other opaque object on top of the fi lm.
4. Wait for two minutes.
5. Process the fi lm as usual.
The processed fi lm should be clear. None of the objects should be visible on the fi lm.
If any of the objects can be seen on the processed fi lm, there is a light leak or other light source in the
darkroom. The light leak fogs the test fi lm, everywhere except where the opaque objects are blocking the
light. To fi nd the light leak, turn all of the lights off in the darkroom and inspect the darkroom for cracks
around the door and ceiling tiles. Indicator lights on equipment, such as stereos, and improper safelights
can also cause fogging. Turn off all unnecessary equipment and the safelight and try this test again.
B