Usability of Digital Cameras for Verifying Physically Based ...
Usability of Digital Cameras for Verifying Physically Based ...
Usability of Digital Cameras for Verifying Physically Based ...
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i \ j 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15<br />
0 26.16<br />
1 25.12<br />
2 25.53<br />
3 24.76<br />
4 25.63<br />
24.57<br />
23.67<br />
23.76<br />
22.90<br />
23.80<br />
23.32<br />
22.08<br />
21.06<br />
19.73<br />
19.67<br />
19.84<br />
18.92<br />
17.64<br />
16.26<br />
16.35<br />
16.31<br />
16.05<br />
14.77<br />
14.02<br />
14.17<br />
14.74<br />
14.10<br />
12.51<br />
11.61<br />
11.43<br />
13.69<br />
12.97<br />
11.19<br />
9.52<br />
9.12<br />
11.59<br />
13.37<br />
12.93<br />
10.06<br />
6.28<br />
Table 3: Standard deviation <strong>of</strong> all 80 submatrices <strong>for</strong> D65 and dimmer setting<br />
100%.<br />
11.59<br />
13.37<br />
12.93<br />
10.06<br />
6.28<br />
In order to find the optimal position <strong>for</strong> placing the color chart, we were<br />
searching <strong>for</strong> a subarea <strong>of</strong> the size <strong>of</strong> a color chart, where the standard deviation<br />
<strong>of</strong> the difference in luminance distribution is minimal. The GretagMacbeth Color<br />
Checker SG has 4x5 white patches in the boarder area. As we chose our meas-<br />
urement points according to the distance between two <strong>of</strong> those white patches, we<br />
have to find the 4x5 submatrix in our 8x20 matrix <strong>of</strong> measurements, that has the<br />
smallest standard deviation. The number <strong>of</strong> possible candidates is 80, as we have<br />
5 submatrices in vertical direction and 16 submatrices in horizontal direction. We<br />
simply calculate the standard deviation <strong>for</strong> all possible submatrices and choose<br />
the one with the smallest result. Tables 3, 4, 5 and 6 show the results <strong>of</strong> these<br />
calculations; the smallest results are emphasized. For the submatrices with the<br />
most even luminance difference distribution the standard deviations are 6.28 <strong>for</strong><br />
dimmer setting 100%, 1.61 <strong>for</strong> 50%, 1.12 <strong>for</strong> 25% and 0.96 <strong>for</strong> 15%. Figure 42<br />
shows Mathematica plots <strong>of</strong> the same results. These results clearly show that <strong>for</strong><br />
D65 the best position <strong>for</strong> the color chart is in the middle part <strong>of</strong> the front region.<br />
Our results <strong>for</strong> lightsource 840 at dimmer settings 100% and 50% are shown<br />
in figure 43 (a) and (b). Again we scaled the values <strong>of</strong> 50% by 2 (see figure 43<br />
(c)) and visualized the difference to the values <strong>of</strong> 100% (d). Figure 44 shows<br />
the according plots <strong>for</strong> lightsource CWF. Standard deviation <strong>for</strong> dimmer settings<br />
100% and 50% are shown in figures 45 (840) and 46 (CWF). The maximum values<br />
are 40.39 cd/m 2 (840) and 40.30 cd/m 2 (CWF), which is considerably higher<br />
than 26.16 cd/m 2 <strong>for</strong> D65. The lowest values <strong>for</strong> 840 are also in the middle part<br />
60<br />
13.69<br />
12.97<br />
11.19<br />
9.52<br />
9.12<br />
14.74<br />
14.10<br />
12.51<br />
11.61<br />
11.43<br />
16.31<br />
16.05<br />
14.77<br />
14.02<br />
14.17<br />
19.84<br />
18.92<br />
17.64<br />
16.26<br />
16.35<br />
23.32<br />
22.08<br />
21.06<br />
19.73<br />
19.67<br />
24.57<br />
23.67<br />
23.76<br />
22.90<br />
23.80<br />
26.16<br />
25.12<br />
25.53<br />
24.76<br />
25.63
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