Differences in perception between projector projections in hybrid images

Hybrid images[1] are images created by combining two images, a high-frequency image that is easy to recognize from a close distance and a low-frequency image that is easy to recognize from a far distance, so that different images can be seen depending on the viewing distance.
On the basis of these previous studies, this study investigates whether there is a difference in the way hybrid images are perceived depending on the medium in which they are drawn. In fact, we investigated the difference between the perception of the hybrid image when it is viewed and the hybrid image created when it is projected using a projector. The investigation was conducted twice, each time with a black and white hybrid image and with an EPSON-EV100 projector.
The first investigation was a projection mapping of the hybrid image, which was carried out in December 2019. This one investigated whether it is possible to distinguish between high and low frequency images by projecting hybrid images with a projector. When the hybrid image (Fig.1.) was projected on the wall of a shopping center, many people said that it was difficult to distinguish between the high and low frequency images. The following were speculated as the causes: the light level in the exhibition space was difficult to adjust, making it difficult to recognise the pictures themselves; it was difficult to view the images while moving around; and the structure made it difficult to recognise the high and low frequency images from each other.
Based on these results, we conducted a second survey. Unlike the previous study, we adjusted the amount of light in the exhibition space and the size of the projected images to design a viewing space with a shorter viewing distance. In particular, when creating the hybrid image, we tried three different ways of creating a composite of the high and low frequency images: overlapping the characteristic parts of both, reducing the surface where the motifs overlap, and completely overlapping the motifs. As the location of the experiment was a university classroom, the hybrid images (Fig.2.) were displayed in a narrower space from the projection surface, so the images were zoomed to become larger and larger, which was more recognisable than in a shopping mall. In particular, of the three hybrid images, the one created using the "method of overlapping the characteristic parts of both" resulted in the easiest discrimination between the high and low frequency images. The same result was obtained when these images were printed on paper and viewed.
These studies show that it is possible to discriminate between high and low frequency images by projecting and viewing hybrid images. It was also found that the same hybrid image did not differ significantly in recognizability depending on whether it was printed on paper or projected, but that the contrast of the hybrid image when projected on a projector had a significant effect on how it was perceived, depending on the intensity of the colours.