ANSI IT4.31-1998 pdf download Photographic Inertness of Construction Materials – Test Method and Specification
For example, if the average density dfference for corresponding steps between pairs of strips processed on different days is 0.032, the upper control limit is (3.27) (0.032) i.e. 0.1046, or 0.10 when rounded. The lower control limit is 0.00. From this data, it would be expected that virtually any pair of strips, processed under the same conditions on the same day, would not differ in densities at their corresponding steps by more than 0.10. Density differences are absolute values, ie., without regard for sign.
4 Establishing the variability of the photographic test process
4.1 Equipment and techniques Actual processing equipment and techniques can be used if practical. The test shall be representative of the normal process.
4.2 Test strips Select a set of 10 to 20 controlled exposure test strips of a photographic material that is appropriate for the processing solutions being considered. Test strips exposed by the flm or paper manufacturer may be used if such strips are available for the process being considered. To minimize variability due to latent image change, exposed test strips shall be held at least 24 hours at room temperature before use. Control strips and sample test strips shall be handled in a like manner. It is recommended that all strips be kept under refrigeration after the 24-hour holding time and brought to room temperature just prior to use.
4.3 Processing Process two strips separately each day for at least five days.
4.4 Determination of the control limit Measure the densities (as described in either ANSI/ISO 5-4, ANSINAPM IT2.17 or ANSI/ISO 5-2, ANSINAPM IT2.19) of the processed test strips at the fog, minimum, midscale, and maximum density regions. For each pair of strips, determine the difference in density (range) for each of the corresponding density regions (steps). List these density ranges in groups; for example, list the five or more midscale ranges. Calculate the average range of each group, and finally calculate the upper control limit for each group by multiplying the average density range by 3.27. The lower limit is zero for any density region. An example is ilustrated in annex A using red filter densities for color film. Similar density measurements and computations should be made using all filters appropriate for the process concerned.