The Hagner EC1-L Screen Luminance and Film Density Meter is a compact instrument for measuring the luminance of luminous screens, for instance of film and slide viewers, X-ray viewers etc., and for easy calculation of film density. It has both an automatic zeroing and an on/off switch and the only controls needed are a four position range selection switch and a hold button to retain the displayed value.
The opening of the detector, which should be pressed against the screens, has a round aperture with an area of 100mm2. The meter is normally calibrated to read from 1 cd/m2 to 2,000,000 (2x106) cd/m2 in four measurement ranges.
This calibration is suitable for X-ray viewers. Other ranges, for instance from 0.1 - 200,000 cd/m2 can be supplied on request.
The calculation of film density requires also a simple calculator which will give the logarithm to base 10 of a number (LOG10).
Measurement of film density
- Measure the luminance (Ls) of the blank viewing screen and enter into the calculator.
- Measure the luminance (Lf) of the film when placed over the screen.
- Film density is then given by: D = LOG10 (Ls/ Lf)
Screen luminance is 1,352,000 cd/m2
Film luminance is 107.2 cd/m2
Density is D = LOG10 (1,352,000/107.2)=4.1
If the value of screen luminance is stored in the memory of the calculator, the density at several different positions on the film can be calculated very easily.
|Detector||Silicon photodiode Vλ– filtered|
|Measurement range||1 - 2,000,000 cd/m2 or 0,1 - 200,000 cd/m2|
|Accuracy||Better then ±3% (±1 in last digit)|
|Power supply||9 Volt battery type PP3 (lifetime 350 hours)|
|Dimensions||130 x 75 x 35 mm|