Preserving mountain art
Preserving Mountain Art
Photographic and art archives – the challenges of the digital world
by Guest Writer: Tony Riley
We’ve an article by photographer and mountaineer Tony Riley.
Tony looks at some of the challenges in moving to the digital realm, both as a mountain photographer, and from the point of view of handling the large archival collections of mountain photography and art that exists.
Article Copyright Tony Riley – A print version was published in 2007 by The Alpine Club in their Journal.
Digital technology has introduced major changes in photographic imaging, some aspects of which are particularly relevant in the context of mountaineering photography.
It has also enabled new methods for the digital preservation of visual information in heritage collections, and new levels of accuracy in art reproduction.
The changing scientific basis of these topics, from photographic to colour science, should be of interest to all institutions such as the Alpine Club that have photographic and art archives, since funding bodies could increasingly favour digitisation projects that show an awareness of the new scientific guidelines currently in development.
About the Author
Tony Riley qualified in Imaging Science with a dissertation in the measurement of colour difference in art reproduction(9), and he has a special interest in the digital preservation of heritage.
Having spent most of his life as a mountaineering cameraman, professional photographer and lecturer, he has enjoyed photographing mountain areas for over half a century, and now runs an art gallery in the English Lake District.
His website contains further articles on the topics in this paper.
Mountaineering and photography seem to have strangely aligned histories, maybe by developing over a similar period.
Certainly high light levels in mountain regions made them a natural environment for getting the best from the first very slow film emulsions.
Photography and climbing
The unending supply of great pictures in climbing publications is a tribute both to the popularity of photography with climbers, and their documentary and artistic skills. A love of mountains finds natural expression in photography, and few climbing teams are without a camera.
Each advance in camera technology has been rapidly assimilated by climbers, through early rollfilm formats to 35mm then the compact cameras.
They have been slower to change to digital cameras over the fifteen years that consumer models have been available, especially given that digital cameras have been outselling film cameras for the last few years.
There are probably good reasons for the slower uptake of digital cameras in mountaineering, mainly loss of battery power in extreme cold.
But digital cameras actally have some advantages in cold conditions, namely fewer moving parts to freeze, less detail-obscuring image noise or ‘grain’ than film, and the possibility of more accurate colour reproduction.
Right – Blea Tarn – the possibility of more accurate colour with digital.
For the professional cameraman/photographer, film equipment can be degreased and low-viscosity lubricants used to combat freezing. I well remember burying a movie film camera in a snow slope at 25,000ft, rather than carry it back down only to have to haul it up again. I was surprised to find it working a week later.
The purpose of this paper is to draw attention to the advantages of the new science replacing photographic science in digital imaging, rather than trying to compare all digital capture with all film photography. The simplistic answer to this comparison is that some digital images are better quality than some film images, and vice versa.
Photography in the Cold
One advantage of digital cameras used in extreme cold can be a reduction in the ‘grainy’ texture caused by electrical noise in the image signal. This is easily identifiable in digital images in areas of even tone like skies, and shadow areas.
The image to the right shows a magnified crop from a 3200 ISO exposure, which exaggerates the effect.
The improvement at low temperature can be pronounced enough for some scientific digital cameras and professional scanners to incorporate cooling systems to reduce noise in the charge coupled device (CCD) or CMOS sensor that initiates the image capture sequence.
We accept grainy texture in photographic film images, but the better digital camera images are much closer to reality in the sense of reducing this effect, that can have the same effect as film grain in obscuring fine detail.
Film images are also affected adversely by exposure to heat, but the effect is additive, and something that occurs frequently on expeditions.
This can cause both selective and overall colour casts in the colour layers in film emulsions that are designed to work in parallel.
What is the relative colour ‘accuracy’ of digital and film capture?
Film dyes produce a limited range of colour compared to a silicon camera sensor, given the colour gamut of pixel filters and subsequent data processing.
Digital capture also enables more ‘accurate’ colour than photographic film dye, as we see later in looking at the digital preservation of heritage.
Many films also deliberately distort colour rendition and tonal reproduction for aesthetic reasons.
An impeccable scientific experiment (1) in comparative colour accuracy between film and digital sensors, when recording real scenes, placed a custom built IBM system top and a consumer digital SLR second, as having the least colour error.
Although, the ‘subject’ brightness range is the same whether you’re using film or digital sensor, some sensors react to it with a wider inherent dynamic range than some films. Digital sensors also record much lower noisy/grainy images in low light levels, than film. Indeed one method of ISO speed rating for digital cameras is based on the acceptability level of noise in the image (2).
Fortunately, most photography doesn’t have to produce accurate colour, merely a pleasing picture (3), since pictorial images are rarely compared with the original scene, and perceptual processes can be shown to distort colour memory (4).
The great mountain photographer Ansel Adams recognised very early in his work both the way film distorted tonal distribution and how the picture in his mind differed, compared to the way the actual measured light in the scene was distributed tonally.
He sought a way of recording an image that would allow him to print, not the image he ‘saw’ in front of him, but that image in his mind, “previsualisation” as he called it. Working predominantly in monochrome to achieve this, he co-invented the Zone System of exposure, that reinterprets film exposure in the light of perceptual behaviour.
How would Ansel Adams have worked today?
Probably like photographer Joseph Holmes, whose beautiful images (5) also straddle the art/science divide, using colour science and colour management to solve the same problem.
Right – ‘Clearing Winter Storm’ in Yosemite Valley.
Photograph © Joseph Holmes (used with permission)
The disadvantage of film’s photographic science is that it is based in brightness measurement, not measuring colour separately.
Digital photography however is based in colorimetry, which uses the spectral composition of colour, allowing us to separate brightness from colour in the same way that the eye does.
Colorimetry defines colour in terms of it’s spectral content, plotting it in three- dimensional ‘spaces’ that take account both of the spectral sensitivity of the cones in the retina, and the subsequent reworking of this retinal response into a different signal set before the information ever reaches the brain.
Joseph Holmes works with very high quality scans of large format film, and has designed the colour spaces used by many discerning photographers.
I often get asked for suggestions about learning more about the nuts and bolts of Colour Management.
My usual suggestion is Bruce Fraser's Real World Colour Management. My own copy is well thumbed. It's my first port of call if I'm asked a question and I feel I don't quite understand an issue well enough to be absolutely sure of an answer.
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The management of colour refers to the practice of measuring the unique colour characteristics of individual cameras, monitors, scanners and printers with a spectrophotometer, and recording differences in a digital file (or ‘profile’) that can adjust colour appropriately in image production workflows.
Many photographers now use a spectrophotometer to calibrate, profile and monitor their colour workflows. Colour ‘accuracy’ is however crucial when we consider the digital preservation of our heritage collections and art reproduction.
Whereas archivists are rightly concerned with the preservation of the original artwork or artefact, even now creating the UK’s first low oxygen storage facility at the British library, digital preservation is concerned both with capturing and maintaining scientifically accurate image information, for its portability to future technology.
Cameras and scanners sense ‘raw’ image information, but introduce proprietory changes in processing this data, so it is important to record the raw data prior to changes.
The individual characteristics of the capture equipment, including lighting, should be measured for image re-evaluation in future technological systems.
How ‘accurate’ can you get in digitally preserving heritage, and how is it quantified?
Colour can be compared to its reproduction, giving units of colour difference on a scale called, among others, delta E (6).
Up to 2 units of difference are considered imperceptible to human colour vision. From 2 to 5/6 is considered acceptable, and more than this is increasingly unacceptable to the average observer. In the colour science lab, accuracies of less than 1 unit have been achieved.
Archiving and restoration
For institutions like The Alpine Club that archive mountaineering heritage, a relevant science-led revolution is taking place in the digital preservation, archiving and reproduction of heritage imagery.
Traditionally this has been done either by photography, often a large format film transparency that is subsequently scanned, or by scanning direct on a flatbed scanner.
But in trying to freeze the visual appearance in time while the original inevitably continues to change, photographic dyes, lighting and individual film scanner and digital camera filters impart their own colour characteristics.
These characteristics can be measured and included in the metadata (information about the image data) along with the actual visual information.
Images for ‘The Crux’
In 2005, Gordon Stainforth and the author applied ‘digital restoration’ to the images compiled by him for The Crux, a photographic exhibition for Kendal Film Festival.
This presented 25 classic photographs from British mountaineering and rock climbing from 1880 onwards.
A principle of digital restoration is to maintain or even uncover image integrity, meaning to remove artefacts that are added at each image stage as a result of whatever processes it goes through.
We rarely had original material to work from, and were dealing with the grain structure produced by the original film or plate chemical processing, noise from the original film scan or print, noise from a scan of that print, and in some cases the screen dot pattern in scans from a book reproduction added to any characteristics of that scanning process.
Sometimes a duplicate transparency added its own emulsion characteristics to the original film.
Most of the work consisted of grain/ noise reduction with a complicated sharpening process that incorporated some image processing.
Although not used for The Crux exhibition, digital restoration can also include Fourier processing.
This is the image processing version of the hi-fi filter that removes ‘crackle’ from audio recordings.
The work enabled us to clarify a third figure and section of rope in the Abrahams brothers’ 1915 Scafell Central Buttress picture, that wasn’t clear in the scan we had to work from.
The most fascinating and difficult picture by far for me was T. Howard Somervell’s picture of Edward Norton at 28,100ft on Everest in 1924, and I did slightly lighten the area surrounding the figure to help distinguish it from the background.(detail – right)
The area round the ice axe remains particularly puzzling. It helps to be a mountaineer in restoring mountaineering pictures.
There comes a point working close in where it is difficult to tell if certain image detail is actual rock detail against the snow, debris left from film processing chemistry, or system noise looking similar to film grain.
Rock against snow has a characteristic feel to how it looks; the bottom line is – if unsure, leave it in.
Colour science isn’t new, but digital colour is, and when it was realised that their combination could provide significantly improved digital preservation of the visual information in art and other heritage collections and archives, there was an explosion in the funding made available for research.
Digital capture and reproduction
Art reproduction has become a hot topic in colour science labs worldwide, and perhaps leading the research is the Rochester Institute of Technology’s Munsell Color Science Laboratory (MCSL).
Together with the Image Permanence Institute, MCSL recently completed a survey in benchmarking the digital capture of artwork in 52 American museums (7).
The study is remarkable both in defining the problem (current practice being based in photographic science, with different institutions taking their own approach), and the answer (colour science methodology plus an art historian).
The report notes the dedication of staff but many inconsistencies in imaging practice, and a lack of understanding of colour science principles.
It also gives a recommended best- practice methodology for institutions that are unable to provide scientific skills or facilities.
Since the background work culture of these scientists is that of ISO committees in photography and imaging, it seems reasonable to predict an eventual ISO standard for the digital preservation of heritage.
The change from photographic to colour science is not yet widely reflected in best practice advice to archivists, and funding bodies could well begin to favour digitisation projects from institutions that show an awareness of the scientific lead being given, and that show they are following the practical guidelines.
It’s also possible of course for the applicant to educate those supplying the funds.
A major problem in digitising photographic collections can be the scale of such projects, especially if planned at print resolutions.
The Paul Nunn Archive for example, recently donated by his family to The Fell and Rock Club, contains over 17,000 images.
I would propose that for digitisation, such projects are scaled down into stages.
Large collections can be batch processed relatively cheaply direct to low resolution, but scientifically more accurate, ‘raw’ files.
This gives a good quality, repurposable, thumbnail image collection that enables cataloguing of the content, perhaps as a basis for selection of the important material for a high resolution digitisation funding application.
It also enables the selection of individual images for higher resolution scanning for specific purposes.
Above all, it makes archives accessible without the cost of a large scale digitisation project, rather than them being hidden away.
The new technology has other advantages for institutions concerned with heritage preservation. It gives electronic accessibility via internet websites where art artefacts are fragile.
A state-of-the-art example is the Vatican Library Project (8), which was able to make previously unseen art available worldwide.
Content management system websites now enable easily-managed picture galleries that can hold thousands of images.
Also, superb quality short-run art reproductions are available via digital inkjet printing.
Because the process is not designed for mass print runs, much better quality inks, pigments, art papers and paper receiver coatings can be used, and a properly produced fine art print can now have a longevity rating (period before discernible fade) in excess of 100 years for colour and 200 years for B/W.
So, should you chuck the film camera away? Well I haven’t yet, but it is gathering dust.
- (1) Berns, R. S. (2001). The science of digitizing paintings for color-accurate image archives: A review. J. Imaging Sci. Technol. 45
- (2) ISO 12232, (1998). Photography – Digital still cameras – Determination of exposure index, ISO speed ratings, standard output sensitivity, and recommended exposure index
- (3) Hunt R.W.G., (2004). The Reproduction of Colour. Wiley (6th Ed.)
- (4) Fairchild M.D., (1998). Color Appearance Models. Addison-Wesley, Reading, Massachusetts
- (5) Joseph Holmes http://www.josephholmes.com/index.html
- (6) Stokes, M., Fairchild, M.D., and Berns, R.S. (1992). Colorimetrically Quantified Tolerances for Pictorial Images. Proc Tech Assoc Graphic Arts part 2
- (7) Berns R.S. and Frey F.S., (2005). Direct Digital Capture of Cultural Heritage – Benchmarking American Museum Practices and Defining Future Needs, Rochester Institute of Technology
- (8) Mintzer F. et al. (1996). Toward on-line, worldwide access to Vatican Library materials, IBM J.of Research and Development, Vol 40, No. 2
- (9) Riley T., (2003). An evaluation of the colour fidelity of digital hardcopy in the reproduction of a watercolour artist’s work. BSc Degree Dissertation, Univ. Coll. of St.Martins, Lancaster, Dept. of Radiography and Imaging Sciences. Also available as a PDF file from firstname.lastname@example.org
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