Light Metering

1. Know the Process

   Have you ever wondered why your chromes look great on the light table, but so often disappoint you when you see them in print?

   One simple reason is the density range. That transparency can show you a range of more than 6 f/stops from brightest to darkest shadow. Once that image becomes ink on paper, that range drops to the equivalent of 4 f/stops on your light meter. Somewhere in between the two is a color separator who will decide what part of that visual information will have to be lost - someone, in effect, reinterpreting the look of your work. We are going to show you a few simple steps which will help you to gain control over the production process and, ultimately, the way your images appear in print.

2. Measure

   Controlling the reproduction process means to measure the contrast range of your images.

   To reproduce accurately, all important information (from shadow detail to highlight with detail) should fit within 4 metered f/stops. For accurate measurements with large format cameras, you should use a film plane meter. The most important points for you to measure in your image are:

   • The midtone (e.g. Kodak Q-18 gray card)
   • The darkest area where you want to hold detail
   • The brightest area where you want to hold detail

   Remember, the contrast difference between those two points should be no more than 4 f/stops.

   The most accurate way to take an exposure reading is through the lens with a metering probe in the film plane. This means any point can be read and the contrast range determined.

   The practical advantages of reading in the film plane are:

   • The photographer measures behind the camera looking towards the subject, and can concentrate fully on the camera and the image composition.
   • It is unnecessary to calculate exposure lengthening factors (filters, extension, etc.).
   • Exact readings can be taken for the important points in the pictorial composition.

   The photographer decides on the tonal values, uninfluenced by the often varying size of image areas with different luminosity. Maintaining the permissible tonal value tolerances in contrast ranges when taking the shot is a prime requirement for good image rendition.

   

3. Communicate

   Without proper communication, the lithographer has no guidance when interpreting your image:

   1. What detail should he keep, and what can be lost?
   2. What areas should he pay attention to for color balance?
   3. Where is the midtone?

   By simply marking the points you measured on a Polaroid or on a overlay, you can communicate this information to the lithographer. Some of the important information you can relay this way is:

   Midtone, darkest shadow detail and brightest highlight detail.
   • Areas which can go solid black or pure white, no detail necessary.
   • Areas which require special attention for color, such as skin tones or important saturated areas of color.
   • Actual light measurements of specific points, for reference. For example, indicate a point metered as 1 stop above midtones +1, or 2 1/3 stops below as -2 1/3.

   Communication must be approached as a team effort between the photographer, the client, the lithographer and the printer.

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