Capturing images

One of the first steps is to determine what in your collection is to be digitised. The types of materials selected for digitisation will determine the imaging equipment used. Image capture from objects by means of film or a digital camera is a time-consuming process and may require substantial resources. A thorough inventory should be made of existing photographic or film-based materials such as slides and prints to determine whether any of this material can be used for the digitisation project; digitising photographic materials may be preferable because of lower costs if the required results can be attained. Tests should be done on each format to determine the results.

Hardware & software

It is easy to be overwhelmed by the wide selection of digital imaging hardware and software available. However there are many very successful examples of small scale digitisation projects that utilised very basic equipment to successfully digitise collections. In 1997 the Irwin District Historical Society in central Western Australia, began digitising 2,000 of their historic photographs to produce a website and family history database. The  equipment and software they used was basic: a Pentium II, PC with 32 MB RAM, running Windows 95 and Access; a Pentax 35 mm SLR; HP Laserjet printer and flatbed scanner. Much of the equipment was borrowed and some purchased, but the result has been a widely used education database for the local high school and a much visited website - http://www.wn.com.au/idhs/. However even the Irwin District Historical Society spent considerable time researching their software and equipment needs and paid careful attention to the following factors:

Computers

Operating system.

The most popular operating systems for stand-alone systems are Microsoft Windows and Macintosh OS; UNIX is the most common for networked workstations. Consideration must be given to your institution's current platform.

Processor.

Image manipulation software requires substantial computing power. The faster the processor, the more efficient the image manipulation process. The processor should be a recent model to ensure that current image software can run on it and that it will accommodate intensive image editing.

Memory

Also referred to as Random Access Memory or RAM. Advanced imaging software applications normally require three times the image file size; therefore, 30-MB image files require 90 MB of memory. More memory may be required if additional software is used simultaneously. Complex image operations will tend to increase the amount of RAM required.

Hard disk space.

Allow space not only for the imaging software but also for its working files, work in progress and an accumulation of images. Disk space requirements can be substantial, depending on the image archival process used.

Display monitor.

This is a key part of the system for image processing and verification. Monitors should be as large as possible, be capable of displaying 24-bit colour (16.8 million colours), support a 72 Hz refresh rate, and have a video board with sufficient memory. High-resolution images are often captured at a level that is beyond the capability of the display monitors; therefore, the most advanced display technology should be used, consisting of large monitors (19" or better), and 24-bit display with a corresponding display card.

Archival drive.

Required for archiving master images such as CD-R, DVD-R or tape, if the master images will be written to an offline format. Alternatively, images may be written to a network drive (requires workstation connected to a network drive).

See more on storage devices and media in the Managing Images module.

Scanners

Flatbed scanners. The most popular image capture device for capturing images, the flatbed scanner can be used to capture non-transparent objects and transparent materials such as 35-mm slides unless the quantity of transparent materials warrants a separate film scanner.

The following are some of the features to consider:

Film scanners: Dedicated film scanners may be required if large quantities of transparent materials are to be scanned. Although more expensive than a flatbed scanner, a film scanner will generate a higher quality image because its scanning process is specific to this medium. Although expensive, a film or slide scanner will produce the highest quality digital images. Some film scanners are capable of capturing larger transparency formats, thus producing very high quality digital images. An alternative to a film scanner is a flatbed scanner with a transparency media adapter (TMA). This method will not produce as high a quality a product as the film scanner, but may be sufficient for your needs. The following are some of the features to consider:

See further information on scanning images.

Digital cameras

Digital cameras can be used in the same way as film cameras, eliminating the need for film processing and creating immediate digital images that can be reviewed as soon as they are created. High-end digital cameras are more expensive than flatbed scanners, but less expensive than a film scanner. Like traditional film cameras, digital cameras can be used in different settings, although they are limited in the number of pictures that can be captured at one time because of the large image file sizes required for high-quality purposes. Digital cameras also require intense light sources in a studio setting, which may pose conservation problems for some objects.

Increasingly digital cameras are falling in price, whilst the quality of images they produce is steadily improving. If you intend to only create a web page that contains a small selection of objects, it may be worthwhile buying a digital camera. However, you still get what you pay for. If you spend a small amount of money you will get a camera capable of producing relatively low quality images. Whilst they may be suitable for a website, they may not be useful if in future you wish to publish them in a book, prepare a newspaper advertisement or create a CD ROM.

When buying a digital camera the following are features to consider:

See further information on digital cameras.

Scanners and digital cameras can be used to capture many of the same formats such as prints, documents, large maps, etc. For some items, a digital camera may be more appropriate than a scanner, whereas a scanner may be better suited for capturing other objects.

See further information on scanners vs. digital cameras.

Traditional film

It is possible to capture images of two and three-dimensional objects using traditional film cameras, then digitise the film images with a scanner. If your institution already has a photographic process in place, with an experienced photographer, you may want to continue using the traditional film format. Careful consideration must be given to the advantages and disadvantages of each method. Substantial resources will be required for the handling of objects during the photography process. A conservator should advise about the handling of the objects during the photography process.

See further information on film.

Capturing the collections may mean choosing between traditional photography and the new emerging digital photography. Several factors may decide the choice, which may depend on factors such as the available expertise and the use of the images.

See further information on digital vs. analogue cameras.

Imaging software

Although several types of freeware and shareware products are available on the World Wide Web, to optimise images, high-end commercial imaging software such as Adobe PhotoShop should be used. During the image capture process, little or no image enhancements should be made to the master images created for archival purposes. This will ensure that the consistency of the image capture process is retained and will match the recorded information (metadata).

Imaging software should be able to handle all the necessary manipulation of images that is required. The following are some of the features to consider:

• Import and export file formats
• Operations such as cropping, brightness/contrast adjustment, resizing
• Multiple images open at a time
• Ability to handle large size images
• Multiple undo levels
• Batch and macro facilities for repeat operations
• Support for TWAIN or ISIS standards (Click here to see more on software interfaces)
• Save workspace settings to pick up work in progress where it was left off
• Built-in image management 
• Cross platform operation

See further information on image manipulation software.

Printers

There are a range of printers on the market, many of which approach the level of quality you get from traditional photofinishers. However, you need to choose a printer whose capabilities match your needs.

As with cameras and scanners, resolution is the key issue for printers. To print photos, your printer should produce output at 600 dpi or better. High resolution printers produce images that are more realistic and are better at capturing details from your digitised images. Ideally, your printer should be capable of outputting images without sacrificing quality, colour accuracy and resolution.

Getting the best possible image from your printer requires supplies or material that is optimised for that printer or printer technology (e.g. printing inks). In many ways, the paper or transparency film (for overheads) you choose is as important as the printer you select, since creating the best image requires high-quality materials.

See further information on printing images.

Exercise

When you photograph or scan any collection items it is crucial that a range of image details are recorded on an Image Production Record. The process of recording these details will act as a quality control mechanism and ensure that the equipment is correctly calibrated each time. The recorded information will also allow for the production of further identical images, should the need arise, as all the crucial settings will be known. As a way of familiarising yourself with this process you may wish to take a sample set of between ten and twenty potential images and see if you can fill in the following details:

Sample Image Production Record

Image Production Record. Date_________________

Sample record adapted from www.rlg.org/preserv/diginews/diginews4-1.html William Blake Archive and Western Australian Museum Digitisation Workshop.

This sample Image Production Record was developed for film materials. It can be adapted for other materials and to your project needs.

 Do you understand:

• Which equipment you will need for your particular project?
• The necessary quality assurance procedures you must set in place?

Date published: 1 August 2001