The problem of missing separation records.

In processes where separations were made for permanent safe keeping [from colour negatives or as PM’s -protection masters - from camera original separations] just one is rarely lost. In the Technicolor process it seems that one separation was sometimes removed from storage on it’s own, just for a grader to check something, and never returned, or returned to a new location and lost. Surprisingly often, a laboratory is called on make a new print or modern colour negative from two separations.

Usually a third separation must be made - a neutral, balanced positive can never be produced from two separation records, if the usual colour duplicate negative exposure methods of red record through red filter, green through green and blue through blue, is used.

However, a reasonable result can be made by using different “primaries” in much the same manner as the two colour system worked. This is particularly effective if the Blue record is lost. The red record is exposed through a Red/Orange primary filter and the Green through a Green/Cyan primary filter. Both Kodak Wratten and Lee make filters of this character.

If a green record is lost a surprisingly good result can be made by producing a new separation from a combined, i.e. a contact overlay, of the other two! Presumably this is due to the fact that green is visually the brightest colour visually and combining the other two approaches the relative brightness of neutral colours. Combining the other two works less well in other cases. Using one separation for two colour exposures works to some extent if the green is also used to also make a blue record at a lower final print exposure. Although it is usually possible to achieve neutral greys and so the overall print appears “correct” or “to balance”, some or many colours may be inaccurate!

Loss of the red separation is the most serious, resulting in the least acceptable result.