Polaroid film

The authors also demonstrated a low-technology method for recording the chemiluminescent signal of the bDNA assay. The light emission was recorded on black-and-white film Polaroid film using a handheld camera. The bDNA assay could be applicable to field situations because of the stability of the reagents and the ability to record the data without the use of sophisticated equipment. 

X-ray film or the strips were placed in the mask of the camera luminometer loaded with the high-speed Polaroid film. After the strips were exposed to the photographic material for 10-15 min, the film was pulled from the film holder and after 45 s (processing time) the film backing was removed to reveal the developed image. 

A still more useful improvement is in increased sensitivity. Exposure indices (El) or film speed now easily attain the range of 2000 to 5000, an increase of 10 fold over former high-speed films. With vigorous film processing at high temperatures, color and black white films have been successfully exposed at an El of 6400. Hie use of Polaroid film continues to expand with a soon-to-be-. available fast film effectively equal in speed to 50,000... 

Preliminary X-ray photographs (polaroid film or electronic area detector). 

The fibers were annealed at 200 C for 5 min. in N2, wound parallel on a sample holder and flat plate X-ray photographs taken by exposing the fibers for 1 h (WAXS) to a beam collimated at 90° to the fiber axis, uatorial diffractometer traces of uniaxially oriented fibers were taken uring slit collimation. WAXS patterns were obtained on polaroid film and the difoctometer traces with a Siemens X-ray system. Nickel filtered CuKa radiation was used. The X-ray unit was operated at 30 KV and 20 mA. The sample to film distance was 71.4 mm. 

Polaroid , the material of which most polarizers are currently made, is composed of a clear sheet of polyvinyl alcohol. It is stretched in one direction to align the molecules and dyed with iodine molecules that align themselves along the polymer molecules. This polaroid film will transmit light only in a direction perpendicular to that in which the film was stretched. Polaroid was first made in 1928 by Edwin Herbert Land from quinine sulfate periodide. " The initial idea for this came from the observation of William Bird Herapath that when iodine is dropped in the urine of a dog that has been fed on quinine, shiny green crystals (now referred to as herapathite) with strongly polarizing properties are formed. 

The Polaroid Land rapid-process system of photography has been adapted to some kinds of diffraction equipment. The Polaroid film is backed by an intensifying screen (Sec. 5-2) which converts x-rays to visible light that can darken the film. X-ray exposures are about one tenth of those required by x-ray film, and finished prints are available about ten seconds after the x-ray exposure. 

The convenhonal spectrometer consisted of a Coderg double monochromator equipped with a cooled PMT and was described in detail by Brooker et al. (1994). A 1 W laser was required to obtain spectra with adequate signal to noise ratio. A half-wave plate controlled the polarization of the incident beam. The 90° scattered light was analyzed with Polaroid films with accepted parallel or perpendicular polarized light. A quarter wave-plate in front of the entrance slit served to compensate for grating polarization preference. 

Film contrast is a component of overall image contrast and depends on the type of film used. The density response characteristics of X-ray films are superior to those of Polaroid films and provide the greatest film contrast, thus adding to the overall contrast. Developing and processing of exposed films may add artifacts to the image and, therefore, should be carried out carefully. 

For photography, Polaroid film is particularly useful. Type 47 film has a speed of 3000, and even with an ordinary //l.9 lens exposure times may be as short as two minutes. Lenses with focal ratios of unity or less have, however, been used in fluoroscopy and television and are available from such companies as Wray (Optical Works) Ltd., Farrand Optical and Old Delft. 35 mm cameras with//0.95 optics are also on the market (Canon Camera Company), but these use standard film, which is both slower and less convenient. 

Chemiluminescence is recorded widi Polaroid film type 84, or any suitable film such as Kodak XRP or Hyperfilm-ECL (Amersham, Arlington Heights, IL). 

Decay signals were detected with a photomultiplier tube and oscilloscope, and the oscilloscope traces were photographed on Polaroid film. 

It is usual to collect as many as possible of the emitted photons without the use of optical filters or monochromators. Screening devices using photographic detection have been developed. Sensitive Polaroid films allow the convenient qualitative or semiquantitative monitoring of chemiluminescent reactions. 

A polarimeter consists of a monochromatic light source, a polarizing filter and an analyzing filter (each made of calcite or Polaroid film), and a sample tube (Figure 3.7). If the sample tube is empty, the intensity of the light reaching the eye is at its minimum... 

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