The film is loosely based on the book De Profundis Valsa Lenta [Into the Deepness, Slow Waltz] by José Cardoso Pires (JCP) published in 1997. The book is an autobiography retelling the period in which JCP, an already established author, forgot who he was and who other people were, and forgot how to speak, write and read. This happened in result of a blood clot in his brain, to which the author fully recovered to the point of being able to write about it. The film starts in 1995, the day he woke up "feeling funny" and gradually plunged into another realm of white shadows as he describes it. The film then progresses to show us the challenges he and his family went through during this period, and intercalates with flashbacks that give us more details of JCP’s life and scenes of “real Lisbon” that inspired scenes and characters in his books. Sometimes we go back to the 1950s and see how he and his wife Edite met or when the censorship office “informed” him of the changes needed in his latest book. Sometimes we go back to the 1970s and find JCP talking with one of the Captains of the 1974 Carnation Revolution that ended the Estado Novo [New State] right-wing dictatorship (1933-1974). 

The primary audience of this film is viewers familiar with Portuguese history and socio-semiotic practices and conventions. They will know that JCP is a writer even if they are unfamiliar with his works. They will be able to recognise spaces such as Lisbon from the panoramic and street view shots, clothes and costumes from the 1950s, 70s and 90s, and the Lisbon taverns that will be difficult to find in present times (2025).
The subtitling of Clear Shadows was planned for film festivals in Europe. The audience was considerably undefined and it included viewers from different socio-semiotic spaces, i.e., different age groups, different countries of origin, different levels of acquaintance with Portuguese history and practices, etc. 

The main challenge was thus to ensure understanding and engagement by an audience to whom little/no common socio-semiotic knowledge could be assumed regarding the aspects mentioned above.

If we have a multimodal text in which meaning is erected through different visual and auditory elements coming together, I argue that we cannot create the conditions for an audience in a different semiotic space to access such text (and the meaning it is expressing) by translating only some of the auditory and visual modes. At times, the level of non-sharedness might come because the audience is deaf or hard of hearing and cannot access the auditory modes. Other times, the level of non-sharedness might come because the audience might not be able to recognise or interpret some of auditory and visual elements.

The very fact that subtitles appear inflexibly in the same place on the screen means that they necessarily reorganise viewing patterns by imposing a different axis between focal points and subtitles (Fox 2016). This new axis is most often divergent (or even the opposite) from the one planned in the source film, potentially interfering with the viewing experience or the ability to notice specific elements on screen. The inflexible placing of subtitles also means that subtitles will often appear on top of the focal point, disrupting or covering important visual elements.

Understanding films as an inherently visual production, it was deemed important to add subtitles that followed as much as possible the visual composition of the film and avoided introducing a different aesthetics onto the film. The integration of subtitles in the film (building on Fox's (2016) term “integrated subtitles”) was thus also achieved through the form and timing in which they were displayed on screen. This was achieved by considering alternative options regarding the subtitles’ colour, font type, font size, effects such as fading and rhythm in which subtitles appear on the screen.