Radiography in Modern Industry - Kodak

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densities. Although these differences exist and must be recognized, the similarities in practicalusage between film and paper radiographs are even more striking. Good practice indicates thatthe exposure given to a radiographic paper is adjusted until the necessary and desirable detailsof the image are distributed along the available density scale of the paper within the constraints ofoptimum reflection viewing.If this is done correctly, it will be noticed that the important details will tend to be found in the midscaleof subjective brightness provided by the density scale of the paper. This is strikingly similarto that of a film radiograph in which the details of a good image tend to be centered around themiddle of the density scale (usually about 2.0). The center point, or aim point, then, is a significantfactor for visualization of detail for both paper and film radiographs--even though the aim pointmay be a different value, and the densities may be reflected or transmitted.Interpreting Paper RadiographsWhether produced on film or on paper, a radiograph containing useful information must beviewed by an observer for the purpose of interpretation. The viewing process is, therefore, asubjective interpretation based on the variety of densities presented in the radiograph. To performthis function, the eye must obviously be capable of receiving the information contained in theimage. Judgements, likewise, cannot be made if the details cannot be seen.Viewing conditions are obviously of utmost importance in the interpretation of radiographs. As ageneral rule, extraneous reflections from, and shadows over, the area of interest must beavoided, and the general room illumination should be such that it does not impose anyunnecessary eyestrain on the interpreter.When following these general guidelines in viewing film radiographs, then, the light transmittedthrough the radiograph should be sufficient only to see the recorded details. If the light is toobright, it will be blinding; if too dim, the details cannot be seen. The general room illuminationshould be at approximately the same level as that of the light intensity transmitted through theradiograph to avoid shadows, reflections, and undue eyestrain.The natural tendency is to view radiographs on paper, like a photograph, in normal available light.For simple cursory examination this can be done, but since normal available light might beanything from bright sunlight to a single, dim, light bulb, some guidelines are necessary. It hasbeen found from practical experience that radiographic sensitivity can be greatly enhanced if thefollowing guidelines for viewing are observed.1. As noted in the general rule, all extraneous shadows or reflections in the viewing area ofthe radiograph that adversely affect the eyes must be avoided. In fact, a darkened area,minimizing ambient lighting, is desirable.2. Since radiographs on paper must be viewed in reflected light, several sources of reflectedlight have been used successfully. One method is the use of specular light (light focusedfrom a mirror-like reflector) directed at an angle of approximately 30° to the surface of theradiograph from the viewer's side, so that reflected light does not bother the eyes. Lightthat comes from a slide projector is specular light.Other sources are the familiar high-intensity reading light, like a Tensor light, or a spotlight.Another type of light that has been found to be very effective is a circular magnifying glassilluminated around the periphery with a circular fluorescent bulb. When using this form ofillumination, the paper radiograph should be inclined at an oblique angle to the light to producethe same specular lighting just discussed. These devices found in drafting rooms as well asmedical examining rooms are usually mounted on some sort of adjustable stand, and have theadvantage of low power magnification on the order of 3X to 5X. The magnifying glass should beRadiography in Modern Industry 180
such that it does not distort the image, but it does emphasize the fact that the graininesscharacteristics of paper radiographs are minimal.Reflection density is different from transmission density. The difference is important in viewingand interpreting radiographs on paper, but presents no difficulty in procedure or visualization.Radiography in Modern Industry 181
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RadiographyinModernIndustry
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RadiographyinModernIndustryFOURTH E
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ContentsIntroduction...............
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Chapter 1: The Radiographic Process
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Intensifying ScreensX-ray and other
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makes it a very suitable material f
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Figure 6: Typical voltage waveforms
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Table I - Typical X-ray Machines an
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The wavelengths (or energies of rad
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Table III - Industrial Gamma-Ray So
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1. The source of light should be sm
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B and H in the Figure 13 show the e
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Figure 14: Geometric construction f
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Figure 17: Pinhole pictures of the
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The kilovoltage applied to the x-ra
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Figure 21: Schematic diagram of som
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kind of material radiographed, the
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instance, the kilovoltage may be fi
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The technique need not be limited t
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Chapter 5: Radiographic ScreensWhen
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Contact between the film and the le
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Figure 29: The number of electrons
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lead foil screens ran be retained w
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Figure 33: The sharpness of the rad
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Figure 34: Low density (right) is a
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such as a wall or floor, on the fil
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from this source. Since scatter als
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A filter reduces excessive subject
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Definite rules as to filter thickne
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0.010-inch front screen of value be
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Example: Suppose that with a given
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If the milliamperage remains consta
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espectively. In other words, a cons
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Any given exposure chart applies to
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Figure 46: Typical gamma-ray exposu
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where the slope of the characterist
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Figure 49: Characteristic curves of
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Figure 51: Characteristic curve of
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Nomogram MethodsIn Figure 54, the s
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Figure 56: Transparent overlay posi
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Figure 58: Overlay positioned so as
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The problem of radiographing a part
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Figure 62: System of lines drawn on
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Chapter 8: Radiographic Image Quali
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Film contrast refers to the slope (
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Hole Type PenetrametersThe common p
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of the same thickness as the specim
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Chapter 9: Industrial X-ray FilmsMo
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Figure 70 indicates the direction t
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the lead letters on a radiation-abs
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Therefore, protection requirements
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5. Avoid pressure damage caused by
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Paddles or plunger-type agitators a
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slow, and the development time reco
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ubbles make their way to the surfac
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When development is complete, the f
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soften considerably with prolonged
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Figure 77: The roller transport sys
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Rapid Access to Processed Radiograp
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Figure 78: Film-feeding procedures
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Chapter 11: Process ControlUsers of
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3. Age of the developer replenisher
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Figure 80: Control chart below for
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DiscussionDensitometric data and pr
Page 129 and 130: Figure 82: Plan of a manual x-ray p
Page 131 and 132: Figure 83: A schematic diagram of a
Page 133 and 134: loading-bench activities are carrie
Page 135 and 136: KODAK Quinone-Thiosulfate Intensifi
Page 137 and 138: Methylene-Blue MethodTwo variations
Page 139 and 140: KODAK Hypo Test Solution HT-2Avoird
Page 141 and 142: In summary, use of the test papers
Page 143 and 144: narrow angle would be very thick, e
Page 145 and 146: When radiation passes through a spe
Page 147 and 148: Figure 89: Demonstration of the eff
Page 149 and 150: Figure 90: The amount of gamma radi
Page 151 and 152: The radiograph exposed in the right
Page 153 and 154: To illustrate, let us assume that t
Page 155 and 156: Figure 95: High-speed x-ray picture
Page 157 and 158: Figure 97: Two methods of neutron r
Page 159 and 160: Duplicating RadiographsSimultaneous
Page 161 and 162: Sometimes, as when sets of referenc
Page 163 and 164: PhotofluorographyIn photofluorograp
Page 165 and 166: discontinuities or of segregation i
Page 167 and 168: from the camera or by reaching down
Page 169 and 170: Figure 106: Schematic diagram of th
Page 171 and 172: valuable technique, for instance, i
Page 173 and 174: The position of the spots is determ
Page 175 and 176: Powder Diffraction File, Internatio
Page 177 and 178: Processing TechniquesRadiographs on
Page 179: Since this formula applies only to
Page 183 and 184: Figure 113: A: Representation of a
Page 185 and 186: Figure 115: Characteristic curve of
Page 187 and 188: film fairly well. If high densities
Page 189 and 190: Density = 1.5 Density = 2.5Film Rel
Page 191 and 192: In most industrial radiography, the
Page 193 and 194: e noted here. Although the average
Page 195 and 196: Chapter 17: Film Graininess; Signal
Page 197 and 198: The ratio of signal to noise has a
Page 199 and 200: Chapter 18: The Photographic Latent
Page 201 and 202: Thus, the change that makes an expo
Page 203 and 204: Figure 130: Stages in the developme
Page 205 and 206: electrons by successive Compton int
Page 207 and 208: Development is essentially a chemic
Page 209 and 210: Chapter 19: ProtectionOne of the mo
Page 211 and 212: duct is brought into the x-ray room
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