The final part of the zone system trinity is development time. For much the same reason as film speed is personal, so too is the 'normal' development time. The right personal time for any developer you use is very simply established. Use exactly the same shooting and processing procedure as you did to find true film speed. Indeed, it is convenient to do it at the same time. When making exposures of the test target, as well as doing those at zone I, just off black, make some bracketed exposures at zone IX, just off white, by increasing the indicated zone V exposure by four stops. Keep notes of the various exposures. You will probably need two more rolls or sets of sheets with zone IX exposures too, so save time and eliminate variables by making them at the same time. Process the first film for 20% less than the maker's stated time, as described for the film speed test. Find the bracketed exposure at zone IX that is the same film speed as the zone I exposure that proved by test to be the real film speed; i.e. if the true zone I negative was one stop slower than thc maker's speed, find the zone IX frame that is also exposed at one stop less than the maker's speed. Print this frame exactly the same as the zone I frame, i.e. at the same intermittent print exposure and with the same processing. Logically, this print at zone IX should be a very pale grey barely different from white. To check this, process a piece of unexposed paper in the same way and dry them both before comparison. If there is no difference, the film is overdeveloped, ie the zone IX negative frame has too much density and is printing as zone X (white). Remember, development has a progressively greater effect the higher up the zone range you go. In this case, you will need to cut development (try a further 10% cut) and repeat the test. On the other hand, if the zone IX print has more than the merest trace of grey tone, the development time was too short causing zone IX to print too dark, and you should extend it by, say, 10% and try the print test again. Usually with two tests like this you will be so close that you can make a very accurate estimate of the precise development time needed for a zone IX exposure to print as zone IX grey. This estimate can be verified by a further test usually tagged on the end of a film or set of sheets in normal use. . This procedure establishes your normal ('N') development time. I have never known a case where the correct time proved to be more than the maker's stipulation, and it is often less by 30%. Using the maker's time will therefore produce negatives with blocked highlights, and the difference in grain is very marked. I still don't understand why, but the depth of field also seems more with the shorter development - perhaps it's just an illusion. Sometimes when a subject is metered before taking we realise that the brightly lit areas are measuring above zone IX and will therefore print as paper base white, when we need them to show some tone. These tones can be 'pulled in' to printing range by further reducing development time. The exact reduction is found by repeating the development time test, but this time use a frame exposed five stops over the meter's indicated zone V reading to achieve zone X. By finding a development time that yields a print of zone IX grey from the zone X frame, we have compressed the scale by one zone. This is known as N-1 development. To pull in by two zones, retest with a zone XI exposure processed to print as zone IX. This will be your N-2 time. Take care with this amount of compression however. All the zones get compressed and, though proportionately more at the top end, it begins to show badly in the middle tones which can look muddy in the print. Film speeds will probably also fall a little further, requiring either precise further testing or the usually sufficient rule of thumb addition of an extra half stop exposure. In a low contrast scene where the range of subject brightness falls short of all the zones, the contrast can be expanded to fit.

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