Oldal 77 [77]
hel CHARISMA AL.
(a) The RGB values must not exceed 255 grey
levels.
(b) Ifany ofthe pixels are saturated either:
— Move the light sources further away from
the subject
— Stop down the aperture (increase the f- M 66)
stop number) = 11.98
(c) Retake the image until it is not saturated. 121/122
(d) Note that if the lighting conditions or
geometry change, this image should be Figure 2-23
retaken.
White balance
16) Note that the image of the uniform reflective board can also be set as the custom white
balance if required. Follow the manufacturer's instructions for the camera model in use.
17) Otherwise the white balance can be set to a camera standard preset corresponding to
the illumination source being used, (e.g Tungsten). Note that the correct setting here is
not crucial as this can always be modified in post-processing (see Chapter 3).
Obtain the visible-reflected image
18) Set up the image by using either the eyepiece or preferably the live view mode on the
screen if this is available.
19) If using the live view mode, adjust the focus by zooming all the way into the frame.
20) Take the image.
Evaluate the visible-reflected image
21) Check the framing by looking at the image in playback mode.
22) Check the focus by zooming into the image in playback mode.
23) Check the exposure by ensuring that the white patches on the Macbeth colour chart
and the Spectralon diffuse reflectance standards are not saturated. If any of these are
saturated either:
(a) Move the light sources further away from the subject; or
(b) Stop down the aperture (increase the f-stop number)
Retake the image until it is not saturated, and if the lighting conditions or geometry have
changed, retake the image of the uniform reflective board under these conditions.
24) Check the tonal range by checking the image histogram in playback mode.
Version No. 1.0 69 Date : 14/10/2013