Tests of Kodak Films:
Supra 800 vs. Elite Chrome 200
M42 on Supra 800 Film: Normal development, default scan with Polaroid 35Plus:
At this exposure the central Trapezium area is burned out, yet very little of the extensive peripheral nebulosity is visible. Note the marked blue-cyan shift of Supra film when exposed for 20 minutes. While the color could be shifted back toward normal in Photoshop, it was at the cost of shifting the background toward brownish-red.
M42 on Elite Chrome 200 film: Normal development, default scan with Polaroid 35Plus:
Elite Chrome 200 and its identical twin, Ektachrome 200, have been accepted as among the best films for long-exposure astrophotography and this quick-and-dirty M42 shot shows why. Color balance is good and sensitivity to the dim peripheral nebulosity is excellent compared to the Supra 800 (in spite of the fact that negative films generally have greater dynamic range than slide films and the Supra is rated for a daylight speed 4 times greater than the EliteChrome).
To evaluate the effect of metamerism on the apparent shift toward cyan in the M42 emission line source shots above, test shots of star clusters --- presumably emitters of continuous spectrum light --- were made. M13 was shot on Supra 800 (left) and Elite Chrome 200 (right).
Note that Supra 800 again shows a strong shift to cyan, whereas the Elite Chrome remains well-balanced, with younger bluer stars and older yellowish stars well-represented. The faster speed of the Supra is established by the burned out core, but the severe reciprocity failure is revealed by the relative lack of dimmer stars in the periphery. In effect, the reciprocity failure of the Supra results in a shorter dynamic range for Supra 800 than for EliteChrome 200 --- the reverse of what one would expect.
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