Geometric unsharpness, radiographic equivalence factors for exposure technique transfer between metals, and typical steel half-value thickness by energy
◉ ASTM E94/E94M-17 · NOT A REGULATORY SUBMISSION TOOL
⚠ Older edition, and a technique guide with no accept/reject criteria. Source: ASTM E94/E94M-17, read from its own text. The current edition is E94/E94M-22, two revisions ahead of this copy; confirm nothing material changed for your use before relying on it. E94 states plainly that "designation of accept-reject standards is recognized to be within the cognizance of product specifications" (§1.4) — this guide covers exposure technique, not defect acceptance, and has no pass/fail criteria to check against. Table 2's equivalence factors are themselves labelled "approximate" by the standard.
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1. Geometric Unsharpness (§15.1, Eq 1)
U\u1d4d = F\u00b7t / d\u2092. F, t and d\u2092 must be in the same units; source size is usually fixed for a given source, so U\u1d4d is essentially controlled by the d\u2092/t ratio (\u00a715.1).
2. Radiographic Equivalence Factor (Table 2)
Steel is arbitrarily assigned a factor of 1.0. Multiply actual thickness by the factor to get the steel-equivalent thickness for exposure-technique transfer (§8.1); blank cells mean the standard gives no factor for that metal/energy combination.