THERMOCHROMISM OF EKTACHROME-100 PLUS PROFESSIONAL TRANSPARENCIES UPON PROJECTION

Spectral transmittance measurements of single-color Ektachrome 100 Plu s Professional slides were statistically different when measured in a typical spectrophotometer than when projected. Furthermore, the mismat ch was nonuniform and varied for different slide colors. CIELAB Delta E values were as great as 10.3 and frequently were larger than 5, thu s easily perceptible in pictorial images. Instrumental differences acc ounted for an average Delta E(ab) of only 0.3. The spectral changes w ere shown to be thermochromic, caused by heat from the projector light source. Moreover. the thermochromic effect was reversible, although r eversibility was affected by film degradation caused by projection.