This paper gives a concise overview of the techniques we have used to find out the degree of measuring the quality of rendered
images and a level of noise in particular. First part of the paper presents designed and conducted psychophysical experiment involving human
subjective judgment. Then, two of the existing numerical image comparison methods are considered in the context of assessing the level of
noise produced by global illuminations algorithms. The results of the participants' subjective responses are correlated with the data obtained
from objective mathematical metrics. The main goal of research was to determine the objective and perceptual measure of quality for images
with fixed sampling strategy. The results will help to establish the measures of identifying the human perception in the assessment of images
generated with global illumination algorithms.