1 Leaf shutters are usually fitted within a lens assembly (central shutter), or more rarely immediately behind (behind-the-lens shutter) or, even more rarely, in front of a lens, and shut off the beam of light where it is narrow. 2  Focal-plane shutters are mounted near the focal plane and move to uncover the film or sensor.
DHEA levels begin to naturally decline by the age of 30. While normal levels for women in their 20s fall between 65 and 380 Âµg/dL, for women in their 30s and 40s, the average normal range is 45 to 270 and 32 to 240 Âµg/dL, respectively.
A rise or fall in blood urea nitrogen levels may indicate a wide range of health problems. This is because the kidneys and liver are involved in a wide range of body functions. According to the Medical Council of Canada, normal blood urea nitrogen levels range between 7 and 22 milligrams per deciliter. A result higher than 50 milligrams per deciliter is likely to signal an underlying health problem. Elevated BUN levels can result from: