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Chemical   Certification
Plotting Gamma or CI on a Process-Monitoring Chart

Photography (Advanced) - Advanced manual for photography and other graphic techniques
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When  you  are  using  a  new  developing  solution, time-gamma   or   time-contrast   index   charts   (as appropriate) must be developed for the variety of films to be processed in it. Given time, temperature, and agitation for each particular film in the developer, you  will  be  able  to  see  the  results  on  these  time charts. After the developer solution has been proven, you should process a sensitometric strip with each process- ing run. Each sensitometric strip should be read with a densitometer and plotted on the appropriate pro- cess-monitoring chart. As a minimum, you should process and plot a control strip after start-up and before shut down or at the beginning and end of each work  shift.  Once  the  densities  are  recorded  and plotted,  an  accurate  graphic  representation  of  the activity of the process is provided. QUALITY  ASSURANCE CONTROL  CHARTS In  photographic  processing,  control  charts  are  used to monitor the status of specific solutions and the physical process. A list of numbers can be studied carefully to see whether they are out of line; however, when the numbers are plotted on a chart, you can see instantly whether there is data out of order. Photographic quality assurance control charts can be prepared for gamma or contrast index, minimum and maximum density (D-min and D-max), average density (    ), gross fog, temperature, pH, specific gravity, or any other variable that may be required by your quality assurance program. To be useful in your quality  assurance  program,  you  must  collect  and record  data  relative  to  these  and  other  specific factors. From the recorded data, you can calculate the mean or average, and determine the upper and lower limits. If, for example, the control gamma in an aerial film processor is 1.50 and the desired average density is 1.65, you must have a method for indicating when the gamma or     varies to the point where the end result  is  no  longer  desirable.  When  the  gamma tolerance limit is ±0.05 and the    tolerance limit is ±0.07, the control chart appears as shown in figure 2-12. Figure  2-12.—Control  chart. 2-23







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