Basic metering and exposure
Zone 5This page addresses the way a calibrated system responds to metering on a specific subject area (spot metering) and using the resulting meter reading as the exposure. Light meters are calibrated to reproduce subjects as middle grey. Middle grey is the printed value that reflects 18% of the light striking it. At this website, the printed value of middle gray is referred to as either Zone V, Zone 5, middle gray or 18% reflectance. The 18% reflectance value is approximated on the left.

Technically speaking, it is not strictly the case that light meters are calibrated for precisely 18% grey reflectance. Some manufacturers veer slightly from that standard. The amount of departure from the 18% reflectance standard is known as the K-Factor for a particular meter. This presents one of several problems which can be overcome by careful testing and calibration of a photographic system (camera, light meter, shutter, lens, film/developer, enlarger, enlarging timer and photographic paper/developer combinations).

Your light meter and camera are conspiring to reproduce everything as middle gray. The meter has no way of knowing whether it is pointed at a light area or a dark area. The Zone System uses this bit of understanding to build a set of tools which allow you to soar into new regions of photographic control.

So if you want to reproduce something as middle gray, there is a chance it will work. First point your meter at the subject you want to be middle gray, meter on it, then use the indicated reading. That is the exact thing that the meter does for you; it calculates a combination of F-stop and shutter speed, at a given film speed, to reproduce the area it is reading as middle gray.

There are problems getting this to work in real life. Your shutter could be off a bit, the f-stop could be off a bit, the meter could be off a bit, and the film may not react to light at its exact stated film speed. This set of problems can be overcome by carefully testing and calibrating your system. More about calibration and testing later.

A few words about the Zone System simulator
The emulator form and (baseball player) drawing can be used to simulate how a calibrated system will respond if you meter on a given subject area and then expose the film at the indicated light meter reading. The emulator can be further pressed to simulate other concepts that will be covered as we proceed through the real strengths of the Zone System.

In practical terms, achieving the level of calibration represented by this simple simulator is quite challenging. Nevertheless, conceptually, this simulates a key building block in the Zone System.

In a calibrated system, under normal exposure development and print conditions, the subject area that you meter on, will reproduce in the print as middle (18%) grey. Persuade yourself of this by clicking on a subject button below (effectively metering on that subject), then submitting the form to update the picture.

Some of the best information at this site will be found by interacting with the emulator. While the author's best energies at verbalizing the concepts of this material may help augment your understanding of the subject, the thing which needs to be understood is fundamentally visual. The simple emulator will go a long way toward instilling many of the photographic concepts being discussed at this site. However, please do not figure that one or two passes will be enough. A few hundred passes will help. A thousand even more so. Look at the emulator, think about the controls you are applying to the simulator, submit the changes and repeat ad nauseum. Try many combinations. Try to anticipate where each of the five active subject areas will fall on the grayscale. Don't become impatient though. You have to develop skills at counting Fstops, calculating placements and film developments and thinking Zone System thoughts. So go easy on yourself. Actually, there are only about 275 possible drawings with this emulator.

Part of the emulator system is a series of 'helpfiles'. Helpfile 1 will walk you through metering on each possible subject area then reproducing that area as 18% gray in the print. If you are using a small screen, you may prefer to load helpfile1 in a separate window.

About the billboards in the drawing:


The drawing has five interactive areas. The billboards are for fun only. Please keep the flames about the tobacco down y'all, we hail North Carolina after all. However, neither the webmaster nor anyone the webmaster has ever known in the field of medicine recommends that humans consume tobacco in any form. Tobacco smoke is disastrous in the darkroom too. Its presence often causes variations in the print contrast.