I’ve hopefully by now established that the index is a sign with a physical connection to its referent, which might, but may very well but not necessarily also share with it a visual likeness. In my last post, I touched on process as being a key component of indexicality – that it is the process by which something comes into being that makes it indexical or not. If a chemical photograph can be considered an index by virtue of its method of production forcing it to correspond ‘point by point to nature’  can this not also apply to digital media?
Consider a Microsoft Kinect depth sensor. The Kinect works by sending out beams of infra-red light that reflect off objects back towards the sensor, by measuring these beams the computer is able to determine how far the object is from the sensor and construct a virtual 3D model accordingly.  The Kinect records a physical presence in the world using an array of numbers, as anyone who’s ever worked with the Kinect in Processing applications will know. These numbers do not necessarily have to be used to create a 3D model – depending on the software they’re fed into they might be output as colour, or as sounds, or any other expression the programmer chooses – but no matter how they are output the numbers themselves remain constant: forced to correspond point by point to nature.  Does this not constitute an indexical trace?
Susan Sloan has previously argued that motion-capture data acts as a certificate of presence in much the same way that a photograph does; and, therefore, it constitutes an indexical trace.  Furthermore, she points out that motion-capture data is unique to each individual – and although it can be cleaned up in post-production – you cannot capture the motion of no-one in particular, much in the way that you cannot take a photograph of no-one in particular.  It could be argued that the very fact that this data exists proves that something was placed before the sensor, in much the same way that Barthes saw the existence of a photograph as proving the existence of its referent.
However, as Sloan points out, this data can only really resonate with the viewer when it is presented in a form that they can easily comprehend – presented as a line graph for example, the same data has none of the effect it does when applied to an animated figure (as in Sloan’s 2011 work Studies in Stillness).  This does not undermine the data’s potential as an index, as the underlying data remains constant, but highlights its reliance on iconical modes of representation. In other words, for data captured digitally, no matter what it may be, in order for it to resonate with the viewer it must be ‘performed’ as opposed to simply made available.
Boris Groys, who I cited in my PhD proposal, made a similar argument for the digital photograph, the screenic display of which is also a kind of performance. According to Groys, because the digital image is mobile, free to move across networks and be displayed on different screens,  each visualisation is a unique event. Therefore, it is not enough to simply exhibit a digital photograph, it must be “staged, performed” in a manner akin to a musical score.  Interestingly, these are the same terms Ansel Adams used to describe the printing of a negative in the darkroom.  This suggests that there is also an element of staging and performativity inherent in analogue photography.
Assuming for a moment that the kind of data discussed above can be considered an indexical trace, does this not open the door not just for a renewed discussion of the indexicality of the digital photograph, but for other data captured digitally? In the V2_ publication New Aesthetics, New Anxieties, David M. Berry and his collaborators make the following observation:
[…] so far, the New Aesthetic has been presented as screenic images. […] We constantly require attentiveness with such surface reading, as it entails a kind of flattening of the digital. A flattening which may, or may not, have a presumed indexicality such as place and subject. We might also want to think about the metadata implications for a digitally constructed indexicality provided by geo-location, technical specs and so forth embedded in the image. 
Essentially, what the authors are warning against here is the tendency of many works that fall under the loose banner of the ‘New Aesthetic’ to focus too much on the surface of the image – the fact that it is composed of pixels – at the expense of the metadata attached to the ‘back’ of the image. Metadata is intrinsic to digital photography and can be used to establish, for instance, whether or not a photograph was taken in a specific time and place. The authors of New Aesthetics, New Anxieties suggest that this might constitute a “digitally constructed indexicality” in addition to the “presumed” (or as Mary Ann Doane put it “imaginary” indexicality ) already present in the photograph.
Writing in the New Yorker, Craig Mod suggests that photographs without this additional metadata now seem “strangely impoverished”, which suggests that our daily interaction with digital photography are prompting us to expect more than just an image:
[…] networked photography provides access to forms of data that go beyond pixels. This information, like location, weather or even radiation levels, can transform an otherwise innocuous photo of an empty field near Fukushima into an entirely different object. If you begin considering emerging self-metrics that measure, for example your routes through cities, fitness level, social status and state of mind (think Foursquare, Nike+, Facebook and Twitter), you realize that there is a compelling universe of information waiting to be pinned to the back of each image. Once you start thinking of a photograph in these holistic terms, the data quality of stand-alone cameras, no matter how vast their bounty of pixels, seems strangely impoverished. They no longer capture the whole picture.  [my emphasis]
It should go without saying that there is a huge difference between the data taken from a GPS sensor and Facebook, but what’s interesting about Mod’s statement is the emphasis on non-visual data supplementing the photograph. If this data measures a physical quality of the thing photographed, provides some connection to the real, can it be argued that this constitutes an indexical trace? Or is it simply a caption?
 C.S. Peirce, The Essential Peirce: Selected Philosophical Writings, eds. Nathan Houser and Christian Kloesel (Bloomington: Indiana University Press, 1992), 6.
 Using only one Kinect will not give a full 360˚model of an object, only the side facing the Kinect.
 Richard Kolker’s 2013 series Shadows uses a Microsoft Kinect to ‘photograph’ young teenagers. See: http://www.richardkolker.com/shadows1.htm (accessed 4th November 2014).
 Susan Sloan, The Synthetic Photograph [Panel Discussion] (London: The Photographer’s Gallery, 14 March 2013).
 Boris Groys, Art Power (Cambridge, MT: The MIT Press, 2008), 83.
 Ibid, 88.
 Ansel Adams: Photography from the Mountains to the Sea [Exhibition] (London: National Maritime Museum, 2013).
 David M. Berry, et al., New Aesthetics, New Anxieties [Online] (Rotterdam: V2_ Institute, 2012), http://v2.nl/publishing/new-aesthetics-new-anxieties (accessed 11 October 2012).
 Mary Ann Doane, “Introduction,” Differences 18(1) Spring 2007: 5.
 Craig Mod, “Goodbye Cameras” [Online], The New Yorker, 29 December 2013, http://www.newyorker.com/tech/elements/goodbye-cameras (accessed 4 November 2014).