As is all of photography there are no one right way to do things, although seminar speakers may disagree arguing that only their way is the one, true perfect road. I disagree. There is no “my way or the highway” in photography; In my world you get to choose the way that works for you. Even a road less traveled is OK; if it produces the results you want. If it doesn’t, its time to look at some alternatives and fine-tune them to your favored subject matter and preferred way of working.
If we have a hand-held or in-camera manual meter setting of 1/500 sec at f/11 and want to use a slower shutter speed allow for subject or camera motion and set choose 1/125 sec you will have to adjust the aperture (make it smaller) so that that the same (equivalent) amount of light will fall on the sensor. By selecting aperture (Av) or shutter priority (Tv) mode, your camera does the equivalent exposure for you, eliminating the all of the guesswork.
Fifty years ago, a group of investors led by Johnny Weissmuller created a hotel called Los Flamingos that was located on Acapulco’s high cliffs. Areas such as this lanai capture those feelings today and if the porch isn’t 18% gray it’s close enough for a substitute reading. ©2012 Joe Farace
When using the substitution method, you replace an object within the scene with an object of known reflectance, such as a Gray Card and take a reflected-light meter reading from this object. (See Metering Limitations below) You can substitute objects that match the light reflectance quality of the object in the scene. Don’t have a gray card? Back in the film days I used to take a meter reading of grass (if there was any in the scene) and open up one stop but I don’t remember the last time I tried this old “rule of green thumb.”
Metering Limitations. Reflected light meters are calibrated to give an accurate exposure when pointed at subject with reflectivity near 18%; the exact value varies and the details are complex with some handheld meters measuring 12% with other meters at 14%. By placing a Gray Card in the scene to be photographed and taking a reading off of it with a reflected light meter, you can expect consistent exposures but sure be sure to read the fine print instead of just accepting the reading as correct. The instructions packed with the Kodak grey card, for example, contain the following advice about adjusting meter readings:
- Normal subjects: “Increase the indicated exposure by ½ stop.”
- Light subjects: “for very light subjects decrease exposure by 1/ stop”
- Dark subjects: “If the subjects is dark or very dark increase the indicated exposure by one to one and one-half stops.”