The discontinuation of conventional photographic spot-reading transmission densitometers -including the widely adopted X-Rite model 310- due to the rapid decrease in demand for analogic photographic laboratory work has had a broadly felt effect in the conservation community. In the cultural heritage conservation field, instruments like the X-Rite 310 are widely used, specifically in the performance of the Photographic Activity Test (PAT) for the preservation of photographic materials. In the present research, five possible alternate metrics were investigated as substitutes for the increasingly unavailable spot reading transmission densitometers in Status-A readings as mandated by the current PAT. The analyzed metrics were: (1) ratio in reflection using normal illumination geometry and circumferential 45° viewing (0/45:c), (2) contrast ratio in reflection using diffuse illumination and 8° viewing geometry with specular component included (d/8:i), (3) contrast ratio in reflection using diffuse illumination and 8° viewing geometry with specular component excluded (d/8:e), (4) Ortho-transmission densitometry and (5) UV- transmission densitometry.
The contrast ratio metric can be obtained with commonly available reflection spectrophotometers, such as the X-Rite 939 and the X-Rite SP64. The use of contrast ratio metric could open up new possibilities for measurement in the field of art reproduction and cultural heritage preservation to analyze changes in density and opacity. The proposed work analyzed the readings obtained by three measurement instruments: (1) X-Rite 361T, (2) X-Rite 939 and (3) X-Rite SP64, in a set of three achromatic transmission step-wedges (15-Step Transmission Stouffer© Graphic Arts T1530CC step-wedge) used as a surrogate for the colloidal silver strip used in the PAT.
The goal was to evaluate the performance of the five proposed metrics and geometries as a possible alternative to transmission densitometry measurements when recording data using the Photographic Activity Test.
The results indicate that there exists a near-perfect linear relationship between the readings using the X-Rite 361T in Ortho-transmission densitometry channel and the readings from the Status-A transmission density using the X-Rite 310 across the entire densitometric range represented by the Stouffer wedge. The UV channel measurements also exhibit a near seamless linear regression model with the Status-A readings. Both relationships were found to be statistically significant. On the other hand, the measurements with the setups using contrast ratio measurements did not exhibit the same linear relationship when the entire measurement range is considered. However, in readings of less than .95 opacity, the contrast ratio measurements did exhibit a meaningful linear relationship when compared to the Status-A transmission readings with a density value of less than 1.8, albeit still with lower correlation than both readings with the X-Rite 361T.
Library of Congress Subject Headings
Photographs--Conservation and restoration--Equipment and supplies--Evaluation; Densitometry
Print Media (MS)
Department, Program, or Center
School of Media Sciences (CIAS)
Bruce Leigh Myers
Monroy, Ishtar Laguna, "Using the contrast ratio method and achromatic transmission densitometry as a substitute for Status A transmission densitometry with the Photographic Activity Test For Enclosure Materials" (2013). Thesis. Rochester Institute of Technology. Accessed from
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