Las redes sociales corporativas como herramientas en la comunicación interna

The concepts of resolution and colordepth, already mentioned earlier, are crucial when discussing the hardware needed for digitizing films, as these are the two parameters that have the biggest influence on how a film is digitized and how much of its components (in terms of details and colors) will be trans-coded to digital data. Also, these are two critical aspects in the debate on the digitization of archival films within the field, and are often sources of disa-greement.

resolution refers to the capacity of a means of reproduction to describe detail, which can be quantified by measuring the amount of smallest distin-guishable elements in the image. These elements are grain in photography

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and film, and pixels in digital imagery. The higher the number of grain or pixels per frame, the better the capacity to describe detail and, therefore, the

resolution.

While grain in a photograph or in a film frame is a randomly distributed system of crystals of variable dimension and shape, pixels form a system of identical elements arranged in an orderly fashion. The ^resolution of a pho-tochemical system is therefore hard to compare with that of a digital one, as they reproduce images by means of two different forms of representation.

High and low ^resolution in digital imagery are defined in analogy with tra-ditional photography and film. In this phase of the transition to digital, any

resolution below 2^k (where 2^k represents the number of pixels in a horizontal line of the image, namely, 2,000 pixels in width) is considered lower than the

resolution of photochemical film.⁷⁶ In today’s practice, for film production and film archiving 2khas become the accepted minimal required resolution

for a film intended to be shown in cinemas. Although this might change in the near future with the increase of digital storage capacity and of data rate, the agreement on 2^kresolution, although once again transitional, is important because it has been largely accepted and adopted in the practice for at least a decade now and it has recently been adopted also in the dcispecifications and published as a standard by SMPTE.

According to a number of sources, the typical minimal resolution of a modern 35mm color film, expressed in digital terms, is about 4k or 12,750,000 pixels per frame. As stated in the guidelines issued by the European Broad-casters Union (EBU), Preservation and Reuse of Film Material for Television:

Technology is now available to scan and digitize the full information available in film images. Experience with such equipment shows that a pixel pitch of 6µm (about 160 pixels per mm) is considered sufficient to reproduce current film stocks. This corresponds to a scan of 4k x 3k

Example of resolution expressed in photographic grain (left) and digital pixel (right)

| 77 (actually 4096 x 3112) over the full aperture on 35mm film. If film is

scanned at lower resolution (corresponding to a larger pixel spacing), less information is captured and more aliasing artefacts are introduced.

(EBU, 2001: 60)

This statement has been challenged by many, and even the EBU has further commented on it in a supplement to the 2001 document quoted above (EBU, 2004: 10):

There are many opposing views on the resolution and bit depth needed to record film images, and the areas of contention may be summarized by reference to a number of different philosophies. These range from concepts that originate from intrinsic film characteristics (the nature of film and processed film emulsions themselves) to others that take more pragmatic approaches.

Interestingly, the statement above acknowledges “different philosophies”, or rather perspectives, from which one can look at the resolution issue. This is indeed the kind of debate going on in the film archival field with regard to film digitization, for instance, around the question of the number of pixels neces-sary to properly digitize film grain. As will be argued in the next chapters, when discussing technical matters involved in digitization, such as ^resolution, dif-ferent theoretical frameworks and concepts are at play and, depending on the framework of reference, different technical factors can gain more or less relevancy. If, for instance, one film archivist could argue that film is art and that the digitization of a film is acceptable only when it can guarantees that nothing of the original film artifact is “lost in translation”, another archivist could maintain that digitization allows us to reach a larger audience and that is an acceptable trade off for losing something in translation. As discussed in Chapter Two, both positions can be defended and they can even be combined when, on the one hand, long-term preservation of the film artifacts is guaran-teed and, on the other hand, digital access to the same films, even if at lower quality (e.g. lower resolution than film), is made possible.

However, with respect to the resolution issue, according to the guide-lines of the EBU, only a digital reproduction system with a ^resolution equal or superior to 4^k can be an acceptable alternative to film. The figure on page 78 shows the ^resolution expressed in terms of pixels of some rather common formats, from the analog magnetic VHS tape to high ^resolution digital film.

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If the previously mentioned limit of 4k is considered as a standard of refer-ence for safeguarding the integrity of original information of a film, the loss of detail that occurs by copying a film on the various formats is obvious. In terms of pixels, choosing to make a digital copy with a ^resolution of 2^k means los-ing 75% of the original details. This loss is higher than 80% for both television formats (SDTV and HDTV). At the lowest end of the spectrum lies the tradi-tional VHS format in which only 2% of the resolution is preserved.In reality, it is necessary to bear in mind that not all films have the same grain resolution

to start with and that a pixel resolution lower than 4k might be sufficient for the larger part of archival film. Indeed, unfortunately, in most cases they are not original negatives, but just projection prints two or more photographic generations down the line, as the negatives have been lost. Since each photo-chemical duplication results in an unavoidable loss of ^resolution, even when duplicating onto a (potentially) higher ^resolution format, it can be concluded that most archival films in fact have a resolution lower than 4^k. As pointed out in the already mentioned EBU document (2004: 12):

At present 35 mm Academy images on Eastman or Fuji color negative films exceed the capabilities of digital cinema although it is clear that given optimum projection specifications and high quality original mate-rial, digital versions can exceed most multigenerational film duplicates in terms of viewing quality.

Anyway, one of the aims of film archives is to safeguard the integrity of the cin-ematographic heritage. To do so the original information (e.g. image details

Comparison between different formats in terms of pixels (horizontal lines, vertical lines, and area) and of resolution expressed relatively to VHS format (VHS = 1)

| 79 and colors) contained in films should not be lost during digitization. On the other hand, a standard value to quantify the resolution needed for correct digitization of a film does not exist, since for every film (and for every scene or shot within the same film) a different ^resolution might be sufficient to guar-antee that all information is safely digitized.

But^resolution is not all there is to it. Another fundamental concept to be introduced is that of bitdepth, also referred to as colordepth, which defines the capacity of a pixel to describe gray and color tones.A “bit”, short for binary digit, is the smallest unit of data in a computer and consists of a single binary value, either 0 or 1. A pixel able to depict only black and white (2 tones) has a

bitdepth equal to 1. A pixel able to describe also gray tones (256, typically) has a ^{bit depth} of 8. For pixels able to describe tones for the independent colors (red, green and blue) the ^bitdepth is typically 24 (corresponding to 16.777.216 tones).⁷⁷ (See figure 1 in the color insert).

It should be noted that in cinema, differently than in other disciplines like photography or graphic design, a different terminology is in place by which a 24 bit depth is referred to as 8 bit depth.⁷⁸ To complicate things even more, such color combinations can be quantified by means of a linear or logarithmic scale. The latter is much more useful when converting an image from analog to digital:

[…] as all electronic light sensors are linear, they produce an output proportional to the light they see, in this case, representing the transmit-tance of the film. This means a large portion of the numbers describes the black and dark areas, and too few are left for the light areas where

‘banding’ could be a problem – especially after digital processing. Trans-forming the numbers into log[arithmic] by use of a LUT [^{look uptable}] gives a better distribution of the detail between dark and light areas and so offers good rendition over the whole brightness range without having to use more digits. (Pank, 2002:12)

Film digitization is carried out by using a film scanner. This is the first hard-ware used in the process, by which the information of every single frame of cin-ematographic film is translated into digits. The scanners’ maximum capacity of ^resolution today is 6K.

Scanners were originally designed for contemporary production to tize newly shot film for special effects. Nowadays they are mostly used to digi-tize the entire footage to create the ^digital intermediate described earlier in this chapter. Film restorers and laboratory technicians involved in restoration of archival films are not a primary target of hardware manufacturers and they are therefore used to adapt standard equipment for their own goals. In the

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case of scanners, they have adapted the feed system of the film, to be able to handle fragile and shrunken films, where deterioration has made the distance between perforations irregular.

Some of the scanners used for restoration of archival films have also been equipped with a ^{wet gate} to allow partial removal of scratches during digiti-zation, as described earlier. Other solutions have also been introduced, such as the use of diffused light in the gate. It is certainly important to eliminate as many scratches as possible in this early phase of the process because, once digitized, a scratch is treated like any other piece of information contained in the original image. For a computer, there is no difference between a wrin-kle on the lined face of old Buster Keaton and a scratch on the surface of the image. Elimination of scratches during scanning reduces significantly the time needed for digital restoration and the risk of mistakes by the software (e.g. any unintentional removal of image detail).

Scanners’ speed is a point of concern, especially when aiming at a cost-effective workflow. There are scanners today able to scan film at “real-time”, that is to say 24 frames in one second, but this is still slower than some tra-ditional printers. Sometimes with extremely damaged films it is necessary to feed the scanner frame by frame. A modified printer for shrunken and dam-aged film is usually still friendlier than a scanner, and can go through a film with less human intervention.

The use of so-called digital telecines is also possible for digitizing archi-val film. Here the digital grading (discussed in the first part of this chapter in relation to the di process) is carried out during digitization. This practice has the advantage that a lower bitdepth is needed and consequently the resulting files will be smaller. On the other hand, in this way there will be no room left in the digital format for a further refinement of the colors.

dynamic range is another important factor determining the quality of a scan. The ^dynamicrange is the range of tonal difference between the lightest light and darkest dark of an image. It is governed by the ^bitdepth at which a film is digitized and is of course influenced by the system performance of the scanner used. The system performance is the overall quality of the scanner, depending on the quality of its components, in particular of the optics, and on the general level of maintenance. Of course, as in all analog processes, and also for digital ones, the critical judgment of the operator defines the quality of the overall result.

Before discussing the software used for restoring the film image, let us already move to the last step in the chain of the restoration in the digital domain, that of the re-recording of the data back to film. This is done using a special printer that provides a function specular to that of the scanner in the digitization process. Also in this case a machine is used that was not

specifi-| 81 cally designed for film restoration, although here there is not really a

differ-ence in procedure since both for modern productions as for restoration the data is written back on modern film stock. However, one obstacle is created by the fact that every re-recorder is typically pre-calibrated for a limited range of film stocks. In the process of restoration, on the other hand, it is important to have the freedom to choose the type of film stock most suitable for achieving a result as close as possible to the original look. A film stock that gives the best result when reproducing an original film in Technicolor from the 1950s will not necessarily give such good results for a Kinemacolor film of 1912. In a case like this, technical modifications of the equipment become necessary. These kinds of modifications require the creation of specific ^{look up tables} (^lut), which are conversion tables used to transfer information between two related systems. The use of ^lut is functional to the calibration in the whole digital workflow for post-production of a new film as for restoration of an archival one. Calibrated equipment (scanners, monitors, digital projectors and data-to-film re-recording machines) within the same workflow will display the image exactly as it will end up on screen when the film will be ready.