Nowadays, in the process of product development, many designers use advanced 3D graphic tools to create realistic product renderings for evaluation of shapes, colors, and textures of new concepts before building physical mock-up models. In such situations, a viewer needs to be convinced that the synthetic object in the product rendering really exists in reality. The goal of the research was to determine if the techniques such as image-based lighting and background removal could improve the functional realism of product rendering, for products with the materials commonly used in design, compared with standard lighting and original background image. We conducted a psychophysical experiment to measure the realism of computer renderings, by asking subjects to observe the physical models with specific surface treatments before assessing the renderings attempting to illustrate the corresponding materials. The results suggest that the image-based lighting technique significantly improves the functional realism of product renderings with the use of medium reflectivity material while keeping the original background image. On the other hand, standard lighting method contributes to higher realism in the absence of a background.