Oldal 22 [22]
150}
100;
Relative power
50}
e A
0 a 4. 4. a
400 450 500 550 600 650 700
Wavelength A (nm)
Relatíve power
60 Fale — ps0
= DSS
400 450 500 550 600 650 700
Wavelength A (nm)
Figure 1-10. Visible-reflected image of a detail from a wall painting fragment from the British Museum
(Winged youth from the Tomb of the Nasonii, 1883,0505.5) captured with (a) tungsten lamps
(represented by the CIE standard illuminant A) and (b) flashes (represented by the CIE standard
illuminants D50 or D55).°°
The manner in which cameras process images (see Chapter 3, section a) will also have an
effect on the reproducibility of luminance in reflected images. The sensors used in DSLR
cameras are linear, i.e. the number they generate for each pixel is proportional to the
amount of light at that point. However, because the sensitivity of the human eye to light is
different to that of a camera (Figure 1-11(a)), a function, or “gamma” is often applied to the
captured image when this is converted into a standard J PEG or TIFF file by the camera or
Version No. 1.0 Date : 14/10/2013
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