2 Processor monitoring is accomplished with the performance of daily sensitometric tests. These evaluate the performance of both the processor systems and processing chemicals. Sensitometry measures the relationship between the intensity of radiation absorbed by the film and the optical density that is produced.
3 EQUIPMENT NEEDED Sensitometer Densitometer Thermometer Radiographic filmProcessor Control Chart
4 The sensitometer is an instrument designed to expose a reproducible, uniform, optical step-wedge pattern onto a film
5 The densitometer, also known as a transmission densitometer, measures the optical density of a portion of an image with a 0 to 4 scale
6 PROCEDUREA fresh box of film should be selected and dedicated to sensitometric testing only. This box of film is known as the control box and should be clearly labeled and stored under ideal conditions (e.g., no light, ionizing radiation, or chemical fumes).Control Box
7 Expose a sheet of film from the control box with the sensitometer (in the darkroom under the safe light conditions) and process it.Green/blue spectral matching switch. Determine the color sensitivity of your sheet of film.Exposing the film with the improper light color will cause the data obtained fromthe strip to be invalid.
8 Calibrate the densitometer. The display should indicate 0. If not continue adjusting the knob on the arm until you obtain the desired reading of 0 OD.Calibrate the densitometer.Obtain the reading by depressing the arm of the densitometer. No film is being used at this time.
9 Obtain B +F readingThe B + F reading should be obtained from the clear portion of a film .Acceptable limits 0.1 to 0.25
10 Determine the speed indicator This is a measure of the amount of exposure energy necessary to produce an optical density of 1 above the B + F. Once the B + F is determined, find the step with an optical density closest to 1 above this value. The value of this step is always measured and recorded as the speed indicator, regardless of the value obtained. For example, if the B + F is 0.2 on the first day and step 8 of the sensitometry image yields an optical density of 1.27 , then the speed indicator is 1.27.In the next sensitometric reading we just obtain reading from step 18.104.22.1681.32The closest to (B+F) = 1.20
11 Determine Minimum Density 0.31Minimum density (Dmin) or low density (LD). Dmin, or LD, is the optical density of the step closest to 0.25 above the B + F, which approximates the low end of the diagnostic range of optical densities. For example, if the B + F is 0.2 on the first day and step 3 of the sensitometry image yields an optical density of 0.47 , then the Dmin is In the next sensitometric reading we just obtain reading from step 3.0.470.59The closest to (B+F) = 0.45
12 Determine Maximum Density Maximum density (Dmax) or high density (HD). Dmax, or HD, is the optical density of the step closest to 2 above the B + F, which is close to the upper value of the diagnostic density range.. In the next sensitometric reading we just obtain reading from step 15.2.072.242.45The closest to (B+F) = 2.20
13 Contrast indicator or relative density difference (DD) Contrast indicator or relative density difference (DD). Because contrast is defined as the difference among optical densities on the processed image, a contrast indicator can be obtained by calculating the difference between the Dmax and Dmin values during each day's sensitometry test.2.24 – 0.47 = 1.77
14 Once all of the previously mentioned values are determined, they should be plotted on a control chart . This helps monitor chemical activity and processor performance and document the quality control activities for accreditation or government agencies. Because control charts have data plotted for an entire month, any trends in processor performance may appear and need to be addressed.
15 Connect the dots to observe the trend Day 1Day 2Step 15Connect the dots to observe the trendSecond day 1.87 (step 15 –step 3)0.1 above the first day readingStep 32.24 – 0.47 = Place a dot in the middle of the control chart. This is a reference value
16 Plot the Mid Density value on the chart for day 1
18 Day 1Day 2Temperature values for the fixer and developer should be measured with the thermometer. However, in order to avoid the contamination of the chemical solutions these values will be obtained from the processor’s display panel.
19 Plot the H and D curve for the day 1 strip Steps