Using a Printer as a Sensitometer

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A widely used and invaluable technique that is essential in duplication is the production of a "print through". In order to establish that an image is printed onto the required straight-line portion of a duplicating material it is necessary to print a series of exposures from the original material onto the duplicating film. This can be done in several simple ways.

• Print a standard negative that includes a small step wedge, onto the duplication stock. The standard negative can be one produced by the Society of Motion Picture and Television Engineers in USA, or the British Kinematographic Sound and Television Society in the UK, or one produced locally by a laboratory. In every case the grey scale should be large enough to measure with a 3mm densitometer aperture. The steps can be marked as corresponding to the highest and lowest discernible densities that exist within original work images, and used for the density plots in the set-up procedures described below. This procedure is less accurate than using a control strip, as there are fewer steps and it is less easy to interpolate. The standard negative is particularly appropriate to the LAD system.
• A control strip exposed by a sensitometer and processed for process control purposes can be used as a test strip. The steps that correspond to the highest and lowest image densities can be marked on a control strip and the "print through" image of this strip will show the resulting densities. This technique is the one most often used in the 2-point set up procedures that follow.

The procedure is most easily used on a rotary contact printer, but an optical printer can still produce sufficient of each step to be read in a densitometer even though a frame line may obscure some of each step.