You may freely adjust the size of the light spot by defocusing the optical head. However, the size of the spot will not be specified. This value is important to properly evaluate the average Dose accumulated in the illuminated area of the sample. If you can control the light spot diameter, enter the value in Options.
If a precise diameter is provided, the calculated Photometric and Radiometric Doses will be correct.
You may still get valuable time evolution of color change even if the spot size is unknown. However, the characteristics of color change induced by the accumulated dose will be misleading.
