Light Meter Calibration Constant

In your example the second reading is higher because the light meter is picking up light from the other lights in the area.

Light meter calibration constant.

With a flat receptor iso 2720 1974 recommends a range for of 240 to 400 with illuminance in lux. Calibrate option if you have a calibrated light meter or known. The update speed is how often a new measurement is displayed. K is calibration constant per lambert s cosine law if we have a perfect diffuser then reflectance r is r pi l e pi k cwhere l is luminancee is illuminance k is the calibration constant for a reflected meter andc is calibration constant for an incident meter for an 18 gray card r 18.

Set the same iso value e g. A common choice is 12 5 canon nikon and sekonic. 4 time constant options. Properly the meter calibration constant as well as the iso speed should be stated but this seldom is done.

Switch the camera to manual mode and deactivate all functions that affect the exposure. The time constant can be set to 0 5 seconds 1 second 2 seconds or 5 seconds. The light meter then gathers the reflected or incident light levels as per the type used. Graph shows the time depedence of the light.

The app will average the data over the time constant weighting it with a linear fall off over the length of the time constant. Using k 12 5 the relationship between ev at iso 100 and luminance l is then. Hold it down for few seconds while pointing it on the light. A value of 250 is commonly used.

For rapidly changing light levels a lower time constant is best. To calibrate your meter we recommend the following method. Light meter calibration light meters are utilized in a variety of industries and applications including photography cinematography osha compliance security quality assurance photosensitive materials regulatory requirements process controls and clean room standards. Light meter ap 881e light meter for plants illuminance meter lux meters with display 3999 range from 1 300 000lux unit lux fc max min back light data hold data storage by aoputtriver 32 99 32.

Iso 100 in the external exposure meter and the camera and make sure that all correction values are at 0. A flat receptor typically is used for measurement of lighting ratios for measurement of illuminance and occasionally for determining exposure for a flat subject. The incident light calibration constant depends on the type of light receptor. Calibrate a light meter.

Flat cosine responding and hemispherical cardioid responding. Values for the reflected light calibration constant k vary slightly among manufacturers. Firstly you need to hold the meter in front of the subject. Is is almost impossible to measure the amount of light given off by 1 light in the conditions you describe.

Autoscale or manual pinch pan y axis.