We use your earnings and work. history to determine your eligibility. for retirement or disability benefits. or your familyâs eligibility for. survivors benefits when you die. In 2016, you receive one credit for. each $1,260 of earnings, up to the. maximum of four credits per year. Each year the amount of earnings. needed for credits goes up slightly as. average earnings levels increase.
Immersion oil should only be used if you have an immersion oil lens. The lens will actually have oil, immersion or HI (homogeneous immersion) printed on it. Immersion oil is best for viewing samples that are dead or are not moving and no thicker than a few micrometers.
Angle of View (Angular Field) - The area size captured by a photographic lens is expressed as a diagonal angular field called Angle of View. The shorter the focal length of a lens, the wider the angle of view (wideangle), while the longer it becomes, the narrower the angle of view (telephoto). (ref. Field of View) Aperture - Lens opening. The opening in a camera lens through which light passes to expose the film. The size of aperture is either fixed, as in a reflex or catadioptric lens, or adjustable. The aperture size controls depth of field.