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Measurement by the incident method is far more accurate and reliable to establish the correct
exposure setting than the calculating of a mean value obtained with the reflected light measurement in
your camera. In the latter case, the reading depends upon the range of contrasts of the subject.
However, there is not always a uniform distribution of bright and dark areas of equal importance within
the subject. Incident light measurement is also imperative with inaccessible subjects.
For this purpose it is necessary to select a point that has the same lighting level as the subject. And
then a meter reading is taken that lies parallel with the projected connecting line between the actual
subject and the camera. This very convenient method of light metering at a point with the same lighting
level is highly recommended for outdoor shots. The measurement is performed with a complete 180°
turn in front of the camera so that the reading is taken with the meter pointing towards the camera, i.e.
opposite the actual picture shooting direction.
Incident light measurement, i.e. with diffuser, also gives a precise reading of the brightness range of the
lighting. Both kinds of lighting – flash and ambient light – are measured with great accuracy by the
incident light method with diffuser.
In addition to this, the DFM 3 also offers the reflected light measuring method. In this mode the diffuser
dome must be taken off and the meter is pointed from the camera towards the subject. The meter now
only measures with angle of 25 degrees the light reflected by the subject. Consequently, the reading
always depends upon the inherent brightness of the subject!! This means that inherently brighter
subjects are not precisely measured and therefore rendered darker. If readings are to be taken
exclusively by the reflected light measuring method, then it is advantageous for the professional to use a
grey card (18 % reflection) in this mode. The reflected light method is used to measure the subject
contrast which is displayed by the DFM 3 on its analog scale (see Section 3.2.4 Contrast measurement,
page 11).
