## 4 Discussion  
This study's results confirmed that ultra-realistic, snapshot, digital holographic portraits can be recorded using a limited number of cameras. Because of the image interpolation implemented by the neural network, the maximum angle between the two cameras was fixed at 20\({}^{\circ}\); beyond this angle, unnatural deformations appeared. Only seven cameras were required to record a half-parallax portrait and twelve for a full portrait. The images were recorded almost instantaneously, and the models remained perfectly intact without any unnatural eye movements. Complex elements, such as writing, can also be perfectly reproduced.  
The two recorded CHIMERA portraits presented a fine 3D reconstruction of the models' heads, with the full-parallax portrait being the most realistic. However, the half-parallax method has several advantages. It requires fewer cameras and shorter shots (100 ms versus 300 ms), thus resulting in fewer errors. The time required to interpolate all images was also faster (5 min versus several hours), which shortened the time between shooting and delivery of the final hologram to a client. Moreover, when the portrait is hung on a wall, most observers do not perceive that the hologram only contains a horizontal parallax.  
This new camera-based technique has several advantages and is much easier to implement than pulsed lasers for recording portraits of living subjects. These methods do not require expensive lasers or advanced technical holographic skills. As the recording of the images is performed in the light and not in the dark, the operations are easier for both the photographer and model. The recording is so simple that we can consider creating an automated shooting studio or \"holo-booth.\" It is not necessary to record and develop an H1 hologram to assess the final result because the photographs recorded by the cameras can be viewed instantly on a computer screen. The recording time with the pulsed laser was 20 ns, and the model did not move during the shooting. A longer recording time with synchronized USB cameras (100 ms) can sometimes lead to slight model movements. This is not a problem if it is possible to repeat the operation as many times as necessary until the most satisfactory portrait is obtained.  
A pulsed H2 portrait has a spectacular 3D rendition and very high-resolution features; however, it is monochromatic with limited parallax. The CHIMERA portrait had the same 3D rendition characteristics. If the resolution is lower (with 250 \(\upmu\)m hogels) the grid is  
Figure 6: Full-parallax snapshot portrait. The cameras arranged on three levels recorded 12 photographs in less than 300 ms (**a**). After the interpolation of 49,152 images and calculation of the hogels, a 15 \(\times\) 20 cm ultra-realistic, full-color, full-parallax CHIMERA was printed (**b**).  
nearly invisible to the naked eye. The CHIMERA parallax is also more important (up to 120\({}^{\circ}\)) depending on the number of cameras used.  
The largest difference is the addition of colors, which make the portrait much more natural and pleasant for the observer. The use of UV glue to seal the CHIMERA and the use of LED lamps to illuminate them allow faithful reproduction of the original colors, which is very important in the case of realistic human portraits. Moreover, a pulsed H2 portrait is always rendered on a 1:1 scale, whereas a CHIMERA hologram can be printed at all reduced or enlarged sizes. Finally, because the CHIMERA portraits can be used as masters, they can be reproduced in large quantities on industrial photopolymer films and disseminated on a large scale. Furthermore, the portraits were recorded from a series of photos that can be modified using a graphic editor or artificial intelligence program to embellish or rejuvenate the model or change the background. The CHIMERA also allows the printing of black-and-white holograms.