Timer system Accuracy
Ultimate Timer Accuracy
24 December 2009 14:34
There is no point having an accurate meter or time base if other parts of the system or the material characteristics rob you of their benefit.
All our f/stop timers use compensated control: They allow for bulb warm-up and cool-down times, such that, 15 1-second exposures give the same result as 1 15-second exposure. The Analyser always uses a compensated timing system, whereas the StopClock has alternative timing systems. As well as linear and f/stop modes, it also has a compensated mode.
The StopClock also features dry-down compensation and 1/24th f/stop control, the most precise f/stop timing available in the world, for critical applications, usually at high contrast settings. Using a number base of 24, gives useful coarser increments of 1/12, 1/6, 1/4, 1/3 and 1/2 f/stop. Systems that use 1/10th are less friendly - we too had it in our original products but changed over, as customers found it awkward in practice to do familiar fractions.
As soon as a StopClock is coupled to a ZoneMaster meter, it switches over. In this way, irrespective of the enlargement size or aperture, a consistent print in guaranteed from an exposure reading, without new test strips.
Above, an extract from Agfa’s data sheet for Multi-Contrast Classic shows how, just as with film, as light intensity falls, the emulsion’s sensitivity reduces too. (MCC is now manufactured and sold by Adox).
In our research we found faster, cold-tone papers are slightly less affected and warm-tone papers more so by the exposure intensity.
In general, it amounts to an exposure error of about 1/12th stop per stop, 10x greater than the advertised accuracy of some meters, that do not compensate.
The really cool thing is you don’t have to worry about all this, these calculations are going on in the background and your prints just benefit from the results of our in-depth practical knowledge. Just like a Mac, ‘it just works’.
