Final answer:
Option 2: Filtration is an indirect effect on radiation dose rate being used in radiographic imaging. It modifies the spectrum of the x-ray beam, affecting image quality and potential dose, but does not directly alter the dose rate.
Step-by-step explanation:
You've asked which factor is considered to be an indirect effect on the radiation dose rate being used. From the options provided, Filtration is considered an indirect effect. To clarify, filtration is a method used in radiographic imaging to absorb low-energy x-ray photons.
It does not directly alter the dose rate but instead modifies the spectrum of the beam before it reaches the patient or detector, thereby affecting the overall quality of the image and the potential dose. Collimation also indirectly affects the dose by limiting the x-ray beam size, thus minimizing exposure to non-targeted areas. Fluoroscopic room illumination is unrelated to radiation dose but is important for the visualization of fluoroscopic images. On the other hand, kVp (kilovoltage peak) and mA (milliamperes) are direct factors, as they determine the energy and intensity of the x-ray beam, thereby influencing the dose rate administered to the patient.