OXIDATION –Chemical combination of oxygen with other substances. In photography, the loss of activity of developer solutions is due partly to oxidation of the developing agent with oxygen in the air and partly  to  oxidation  with  the  silver  halide  during development. (PIA) PIXEL–The  smallest  single  picture  element  with  which an  image  is  constructed.  The  light-sensitive elements in a CCD (chip) camera. PLANE–A surface which has no curvature; a perfectly flat  surface. PAN (WITH A CAMERA)–During  the  course  of photographing  a  scene,  to  swing  the  camera  around in such a way as to follow the action. Derived from: Panorama.  Camera  pans  are  commonly  described as slow-pan, fast-pan, swish-pan, and jerky-pan. PAPER, VARIABLE CONTRAST–Photographic paper  coated  with  emulsions  having  contrast characteristics  grading  from  soft  to  hard,  depending on the color of the exposing light as modified by a series of filters supplied for that purpose. POLARIZER–An   optical   device   for   converting unpolarized,  or  natural  light,  into  polarized  light. POSITIVE, BLACK AND WHITE–A  photographic image on film, plate, or paper in which light tones appear light and dark tones are rendered dark POSITIVE  FILM–Photographic film, designed for the printing  of  positive  transparencies  from  negatives. POSITIVE PRINT–A print in which the light and dark areas as they exist in the original. PARALLAX–The apparent displacement of an object seen  from  different  points.  Commonly  encountered in photography in the difference between the image seen in the viewfinder and that actually taken by the lens. POTASSIUM   BROMIDE   (BROMIDE   OR POTASH), KBr–White  crystals,  very  soluble  in water.  Used  as  a  restrainer  in  developing  solutions. Also  used  in  bleaches  and  clearing  solutions. PERSISTENCE  OF  VISION–A property of the eye that consists of an inability to detect the flickering of  a  light  that  exceeds  a  certain  critical  frequency. PERSPECTIVE –The relative size and alignment of objects as recorded on a plane surface; the illusion of three dimensions created on a flat surface. POTASSIUM  HYDROXIDE  KOH–Caustic   alkali used as an accelerator in photographic developers. Concentrated  solutions  are  quite  caustic  and  will attack the skin, causing painful burns. Similar to sodium  hydroxide. Al-12 PHOTOELECTRIC  CELL–A cell that converts light energy proportionally into electrical energy. It is used in exposure meters and sound recorders and reproducers. POWER,   RESOLVING–The measure of the ability of a lens, a photographic material, or a combination of both,  to  distinguish  detail  under  certain  specific conditions, among which are the shape and contrast of the target, the quantity of illumination, the exposure  and  the  method  of  processing.  The measure  of  this  ability  is  expressed  in  lines  per millimeter or in angular resolution of a lens. PHOTOMETER –An instrument for measuring the visual intensity of light, specifically for comparing the  relative  intensities  of  light  emitted  from different sources of illumination. (PIA) PREROLL–To start a videotape and let it roll for a few seconds before it is put in the playback or record mode, so the electronic system has time to stabilize. PICKUP TUBE–The  imaging  device  of  a  video  camera that converts light into electrical energy-the video signal. PRESERVATIVE–The  ingredient  of  a  photographic developer  that  protects  it  from  rapid  oxidation. PINHOLE–(l)   Term   applied   to   tiny   spots   in   a photographic  negative;  usually  produced  as  the shadow of a dust particle during exposure, more rarely the result of chemical dust contamination or gas bubble formation in the gelatin layer due to improper processing. (2) Tiny or white or clear areas in a print or drawing material. PRINTER, CONTACT–A photographic printer in which the negative is held in contact with print material during the exposure. The image of a print made with a contact printer is the same size as the image in the negative. PINT,  LIQUID–A unit of capacity equal to 16 fluid ounces,  or  473.17  milliliters. PRINTER, PROJECTION–A photographic printer in which the negative is positioned some distance from the print material; the image being projected onto the print material. The image of a print made with a projection printer is usually larger than the image in the  negative.