*3.3. Exposure and Color Correction*

In cinema, a scientific approach to questions concerning the control of color and exposure when shooting has long been employed. It is common for all image- and videoediting programs to implement procedures with externally calibrated measurements [45], using very accurate meters and different procedures to control EVs, as well as employing Color Checker. These procedures, which are also described in the literature specialized in photogrammetry [29,45] were used in this project to solve the color-characterization problem and to avoid occlusions due to exposure problems. By obtaining RAW and compressed JPEG files simultaneously, a safety margin was established in the acquisition that neutralized the risks associated with working with natural light. In fact, during the days of data capture, the sky was very cloudy in Granada and at times quite dark. The use of RAW files allowed us to vary the exposure values and, to some extent, to correct the fluctuations and prevent over- or under-exposure.

In terms of focus, there is always a moment when the image is zoomed in when the circle of confusion is no longer small enough and, therefore, when further scaling up means losing sharpness. Obtaining the correct focus in the shot is very important both for the subsequent definition of the textures and for the photogrammetry program to determine where the points of interest are, and to be able to identify the homologous points. In this project, according to the previsions made in pre-production, we wanted to ensure a minimum aperture of f/8 in order to obtain a sufficient depth of field. In this way, the details of the decorations (4 cm fretwork or longer muqarnas) could be captured without the need to correct the focus at each rig position. Such a decision implied a trade-off that increased the exposure time, which ran the risk of blurring the edges and consequently of increasing the time needed for stabilization and exposure. This time can be carefully calculated so that it is less than the time that would be invested in an eventual focus correction. An alternative solution would be to increase the sensitivity, which was kept at 100 ASA, but such an operation would have the consequence of increasing the noise in the images, which is detrimental to the unequivocal obtention of homologous points. Finally,

thanks to this set of decisions, it was ensured that the results surpassed what the playback or viewing platforms are currently capable of resolving in terms of fluidity and sharpness. what the playback or viewing platforms are currently capable of resolving in terms of fluidity and sharpness.

determine where the points of interest are, and to be able to identify the homologous points. In this project, according to the previsions made in pre-production, we wanted to ensure a minimum aperture of f/8 in order to obtain a sufficient depth of field. In this way, the details of the decorations (4 cm fretwork or longer muqarnas) could be captured without the need to correct the focus at each rig position. Such a decision implied a tradeoff that increased the exposure time, which ran the risk of blurring the edges and consequently of increasing the time needed for stabilization and exposure. This time can be carefully calculated so that it is less than the time that would be invested in an eventual focus correction. An alternative solution would be to increase the sensitivity, which was kept at 100 ASA, but such an operation would have the consequence of increasing the noise in the images, which is detrimental to the unequivocal obtention of homologous points. Finally, thanks to this set of decisions, it was ensured that the results surpassed

### *3.4. Photorealism 3.4. Photorealism*

Shading and look-dev processes are crucial for making the scenery, assets and characters appear photorealistic on screen, but lighting and environmental effects are also equally important. In this project, a detailed study of each character in the environment, light and optics was carried out (see Figure 13a–c), and such a challenge requires a lot of time with conventional methods, so it is recommended, after the experience, to use a rendering engine for testing. Shading and look-dev processes are crucial for making the scenery, assets and characters appear photorealistic on screen, but lighting and environmental effects are also equally important. In this project, a detailed study of each character in the environment, light and optics was carried out (see Figure 13a–c), and such a challenge requires a lot of time with conventional methods, so it is recommended, after the experience, to use a rendering engine for testing.

*Heritage* **2022**, *4* FOR PEER REVIEW 16

**Figure 13.** (**a**,**b**,**c**). Some of the lighting, framing and environment tests that were carried out with the captive character. Note the variations in the depth of field due to the use of different optics in the simulation. **Figure 13.** (**a**–**c**). Some of the lighting, framing and environment tests that were carried out with the captive character. Note the variations in the depth of field due to the use of different optics in the simulation.

Sometimes a large number of possibilities for configuration or modification can be counterproductive in achieving clarity in the final results, even making them less convincing. Nevertheless, such tools make it possible to obtain well-integrated scenes that give the illusion of coming close to what historical reality must have been like, or what could now be interpreted as such. In this sense, the audiovisual industry's way of proceeding consists of trying to make the integration of the different elements invisible, so that even experts find it difficult to reverse engineer and extract the method that was used to achieve this result. Sometimes a large number of possibilities for configuration or modification can be counterproductive in achieving clarity in the final results, even making them less convincing. Nevertheless, such tools make it possible to obtain well-integrated scenes that give the illusion of coming close to what historical reality must have been like, or what could now be interpreted as such. In this sense, the audiovisual industry's way of proceeding consists of trying to make the integration of the different elements invisible, so that even experts find it difficult to reverse engineer and extract the method that was used to achieve this result.

Photorealism aims to provide the audience with a product that seems natural, such that studies of user experience and acceptance should be considered in order to determine if this is achieved. Strictly speaking, by definition, no image can be photorealistic if it is intended to portray a past era, as it will resemble, at best, what other previous artists have imagined those realities to be. If 3D artists are given the opportunity to work closely with those in charge of the care of monuments and with specialists such as archeologists and architects, many possibilities open up for their conservation, or at least for the simulation of interventions and recreations. Photorealism aims to provide the audience with a product that seems natural, such that studies of user experience and acceptance should be considered in order to determine if this is achieved. Strictly speaking, by definition, no image can be photorealistic if it is intended to portray a past era, as it will resemble, at best, what other previous artists have imagined those realities to be. If 3D artists are given the opportunity to work closely with those in charge of the care of monuments and with specialists such as archeologists andarchitects, many possibilities open up for their conservation, or at least for the simulation

In this project, the starting point was a narrative script that placed the story in the realm of fiction. However, under certain conditions and scales, the use of photorealism is of interventions and recreations.In this project, the starting point was a narrative script that placed the story in therealm of fiction. However, under certain conditions and scales, the use of photorealism is not incompatible with the possibility of obtaining the necessary and sufficient data to make the HBIM of the heritage sites usable by conservators and restorers, from a data-collection method that is more or less accessible and rigorous with the color parameters and with elements of anchorage or location. For the objective of photorealism, accuracy and fidelity are not as important as the feeling of naturalness and coherence with the imagination of the audience.

It is true that the desire for photorealism pushes a project towards obtaining an excessive amount of data, thereby generating problems of manageability. For now, not all systems and formats can handle all of these models and sometimes the rendering capacity is insufficient. However, if the scenes have been set up with consistency and are ambitious, the renderings can be improved and adapted to systems with better performance in the near future.
