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Spatial Frequency Sensitivity

If the constant intensity (brightness) Io is replaced by a sinusoidal grating with increasing spatial frequency (Figure 12a), it is possible to determine the spatial frequency sensitivity. The result is shown in Figure 12b .

Figure 12a Figure 12b Sinusoidal test grating Spatial frequency sensitivity

To translate these data into common terms, consider an "ideal" computer monitor at a viewing distance of 50 cm. The spatial frequency that will give maximum response is at 10 cycles per degree. (See Figure 12b.) The one degree at 50 cm translates to 50 tan(1deg.) = 0.87 cm on the computer screen. Thus the spatial frequency of maximum response fmax = 10 cycles/0.87 cm = 11.46 cycles/cm at this viewing distance. Translating this into a general formula gives:

where d = viewing distance measured in cm.

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