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5) If site constraints allow, position the reference standards as recommended in section b.
A scale may also be inserted in the image if required.
6) If working outside the studio or in the field, use the recommended procedure of “twin”
images, described in section b.
7) Turn on the visible/IR radiation sources and ensure that both the subject and reference
standards are evenly illuminated, checking with a light meter if preferred.
8) If using flashes, set these to their lowest setting and check that these are synchronised
with the camera. The room lights overhead may remain on.
9) If using continuous radiation sources such as tungsten lamps, turn the room lights off
now.
Camera capture settings
10) Camera settings will vary according to the equipment used but some general camera
settings are recommended in section b.
Exposure settings
11) The exact exposure settings will vary with the equipment used but some general
exposure recommendations were made in section b.
12) Particular recommendations for acquiring visible-reflected images:
(a) Aperture settings in the middle of your lens range (e.g. f8) are usually a good
Starting point for maximum sharpness, but choose depth of field according to
dimensionality of subject, as advised in section b;
(b) The high irradiance of visible/IR radiation sources usually allows the use of smaller
apertures (high f-stop number), especially if using flashes;
(c) Shutter speed will vary according to whether continuous radiation sources or
flashes are used but can generally be quite short (e.g. 1/8 sec for continuous
sources and 1/200 for flashes). Adjust this as required for correct exposure.
Obtain an image of the uniform reflective board (If site constraints allow)
13) Place the uniform reflective board so that it is evenly illuminated and fills the frame of
the camera. As far as possible the board should be in the same plane as the subject so
that the illumination on it is representative of the illumination on the object.
14) Focus on the board. Defocus slightly. Take the image.
15) Check the image exposure. The RGB values of the image on the image histogram
(Figure 2-23) in playback mode are a good indicator but note that these values pertain
to the preview J PEG generated by the camera not the RAW data (see Chapter 3).*"
Version No. 1.0 68 Date : 14/10/2013