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Title Page Section 1 Section 2

Image Digitisation

Section 1

Why Digitise?
Discussion on Digitisation
Digitisation Decisions

Why Digitise?

2 Fish - Finding Nemo There are many reasons for digitising images and texts. By digitising something, images for example, we open up a whole new world of analysis. By creating a digital representation of an image we can easily share that image around the world for anyone to view so that they may experience the image and examine it. For example, the Mona Lisa - in the Musee du Louvre a handful of people can see the painting at a time, through digitisation a limitless amount of people can view it. Digitisation also allows reduction in wear and tear on a image, researchers can study an image without ever needing to touch what could be an already very fragile and damaged image. They may even find that they can open up whole new lines of analysis through digitisation as an image can be enhanced and studied in great detail on a computer. The image could even be scanned in a variety of lights to open up hidden secrets to it that were previously naked to the human eye. The potential of digitisation is immense, opening up a whole new realm of accessibility and new forms of study of images. However, it is not a replacement for preservation; we can not just scan the Mona Lisa then throw it away. Because no matter how advanced digitisation gets, no matter how detailed it becomes, it can never replace the actual look and feel of its real life counterpart, the only thing digitisation will never be able to replicate is sentimentality, the emotion of a piece.

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Discussion on Digitisation

Digitisation: the conversion of an analogue artefact into a binary form. This includes taking a photo with a digital camera, scanning, faxing etc. The thing about digitisation is that it can either be done very well or very badly. The key to good digitisation is the care taken at the scanning stage. The more time one spends getting the most accurate copy at scan stage means the less time spent fixing the mistakes of a poor scan stage. There are things to remember to ensure a good scan: Resolution: images are made up of pixels, and resolution determines how many are used in representing the image. Basically the more the better Bit-depth: Bits are the basis of any computer; each pixel has a bit-depth. This determines the range of colours that could be displayed by that pixel. From a monochrome image of just either black or white to millions of varieties of colours - the higher the bit-depth the wider the range of possible colours displayed. File format: The important thing to remember here is what an image is for. For archival copies, one should aim to store all the information about the scanned image, therefore the TIF format it used, here all the information about every pixel is stored. Post archiving an image can be converted to suit its need. The most common file format nowadays is JPEG. JEPGs use mathematical algorithms to reduce the size of an image by displaying only colour visible to the human eye. This leads to high quality looking images with lower file sizes that we could not distinguish from the original. It is because of this that JEPG has become the file format of choice in digital photography. It is a lossy form of file format, but one where ignorance is bliss - we do not actually miss anything that has gone missing. Another popular form of file format is GIF; this is good for simple images that only use a small range of colours such a company logos on the internet. It uses a lossless conversion but because it only displays a few colours, has a small file size. All these factors contribute to the final file size of an image. A high resolution, high bit-depth image stored as a TIF will have a very large file size due to the vast amounts of data stored about each pixel in the image. These large files are mainly archival as they would be too large to effectively use on a day to day basis. However, with high speed internet and faster computers, these archival copies can now be shared very easily, between institutes of higher learning for example. A JPEG of the same image is the most likely culprit to be used for analysis and sharing. A TIF converted to a JPEG at the same resolution would result in a much lower file size, whilst still producing a perfectly good image to work from. When it comes to file size, the best way is to work from the top down. In other words, start with your largest file, decide upon the usage and adjust accordingly - resize, crop the image, change the colour depth, alter the file format. However it must be remembered that when changing the image to always keep a master copy of the archival TIF and once an image has been cut down, it has been cut down. It is much harder to make something bigger once it has been made small.

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Digitisation Decisions

A BLue Sully - Monsters Inc

As previously stated, it is extremely important to get the scanning stage done well to avoid needless time consuming alterations to an image post digitisation. Simple things such as the cleanliness of the scanner can affect the outcome of a digitisation project. Therefore a digitisation project manager must consider many elements when digitising. The ultimate goal of the project must be in the forefront of their mind, what quality of image must they produce? And in many cases it would be best if they thought ahead, should the highest quality be produced in case a future project needs to utilise that better file? The equipment is also a consideration, if the piece being digitised is fragile, should it be photographed rather than scanned. Also what light should the piece be scanned in, based on what research will be done on it. The project manager must also strive to achieve a scan closest to the look of the original as possible, making sure the brightness and contrast of the digital counterpart look the same as its original. More often than not the digital image should be the best achievable, it should have the highest resolution the scanner can actually achieve (not digitally enhanced versions) with the highest bit depth. Because of this the file format for storage should be lossless too. That said, a digitisation project could be as simple as scanning in a photo to send to relatives in an email, in that case, the digitised image could be produced at a lower resolution, with a lower bit-depth and stored as a JPEG to facilitate a smaller file size. The main factors that must always be considered for the best outcome are:

  • Storage capabilities.
  • Purpose (current or future) of the digitised image.
  • Look of digitised image being the same or as close as possible to its real world original.
  • Source of image. Some sources such as newspaper use halftone printing, whereby a series of varying black and white dots are used to create greys, these dots can become very evident in scans, resulting in the rows of dots becoming visible. Likewise, images printed on inkjet printers are made up of dots and can become apparent in the digital image.

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