STANDARD FOR PHOTO DOCUMENTATION Updated 02.01.2002
Image documentation
Image documentation is an important link in work with the protection of rock art. In addition to verbal documentation, the Rock Art Database also includes images in the form of photographs, tracings and sketches.
Photographic documentation should be done in a medium or larger format. It should make use of colour negatives or positive material. Documentation should not be done using a digital camera.
Up to eight photographs from each survey (rock art panel) can be placed in the database.
This means that examples from photographic documentation are placed in the database.
Original material is stored in a separate photo archive, and is recorded in Chapter 4 in the database. This standard is intended as a guide in connection with photographic documentation of rock art. The standard includes a minimum standard for photographic documentation. If a museum or county wishes to expand beyond this point, it is obviously possible for this to be done.
Structure
The photo standard is based on the principle that one can, through seeing the images, obtain an understanding that one is moving from the general to the specific. From the overview photograph that shows the locality in the terrain, overview images of the different panels and down to close-up images of individual figures and excerpts of these.
The photographs should show the position of the locality in the terrain, also including the view from the locality. In addition, one moves closer by photographing the locality, the panel, different motif groups/scenes, the individual figures as well as excerpts of
individual figures if desirable. It is recommended to take photographs/macro-photographs of damages and other special conditions.
There are many opinions about which light conditions, etc. one should have when rock art is photographed. In this photo standard, we have taken into account that conditions are not always optimal when photographing, and it is seldom possible to wait for optimal conditions. In our example, photographs are taken in daylight with strong sun. The IFRAO scale17 or something analogous should be used on selected individual images.
Night photography, photographing of wet rock carvings, chalking of the figures (applies to carvings) before photographing, tracing, etc. are assumed to be documentation
methods of individual figures at a more detailed level. We wish to reiterate that this suggested photo standard represents a minimum standard and that each institution is free to choose motifs/methods in addition to this minimum standard.
Examples
All of the photographs are from the locality Begby in Fredrikstad municipality, Østfold.
The examples illustrate how one approaches the locality first from the general area (overview), then to the level of panel and group and finally down to individual figures.
1. The locality: Overview of the area with the locality
17 Can be requested from the Directorate for Cultural Heritage.
2. Panel I 3. Panel I
4. Panel I, scene/motif group 1
5. Panel I, scene/motif group 1, individual figure
6. Panel I, scene/motif group 1, individual figure with scale
7. Panel I, scene/motif group 1, individual figure (combination figure)
8. Panel I, scene/motif group 1, excerpt of individual figures (combination figure) 9. Panel I, example of run-off
10. Panel I, example of weathering
In addition, one can take additional photos as needed, for example:
11. Illustration photo: Surroundings of the locality 12. Illustration photo: Technique for overview photo 13. Illustration photo: Don’t step on the rock!
Format, resolution and size, digital images
When one scans, it is important to understand that images can be used for different purposes. Images that will be published/printed out have totally different specifications than those that will be placed in the Rock Art Database only for screen viewing. When scanning, many choose to accommodate different types of use for the same image. In this case, one must scan the image in high resolution and then make a copy using the correct screen resolution based on this image. One can always scale DOWN a scanned image, both in terms of resolution and physical (centimetre) size, but cannot scale UP to any extent. If one wishes to scan the image in high resolution for future re-use, such as for publication, it is important to remember that the image files take much more storage space (see below). It is up to the individual institution to decide how this should be done, and it is an advantage to check which routines and formats are used within the institution.
Colour photographs are both scanned and stored in RGB mode. RGB represents colours for screen presentation. If the image will later be published, it must be converted to CMYK, which is colours for publication.
If one has scanned high resolution versions, these can be stored as .TIF and .JPG files.
TIF takes the most space, but preserves the image best. JPG is a compressed format that removes some information in the image. An image file that takes up 4 MB in .TIF format will take up ca. 1.7 MB stored in .JPG format. If one uses .JPG format, it is important to use the highest quality, that is with the least compression. Each time the images are stored again, additional information is lost.
The Rock Art Database only accepts image files that stored in .BMP format. In addition, the file name before the file extension is restricted to eight characters, and excludes the Norwegian letters æ,ø and å. All other letters, all numbers and _ (underline) can be used, for example begby_01.bmp.
Resolution has an effect on the degree of detail and grain density of an image.
Screen resolution is generally 72 dpi (or pixels per inch). It is therefore not necessary for an image shown on screen has a higher resolution than this. If the image will be printed or published, the resolution should generally be as follows:
Colour images: 300 dpi
Grey tone images (black and white photographs): 450 dpi Line drawings (only pure black and pure white): 800 dpi
There is a very close agreement between an image’s centimetre size, resolution and file size. A 5 x 5 cm image will take up 1 MB at 300 dpi (dots per inch), while a 10 x 10 cm image will usually “take up” 4 MB. The same 10 x 10 cm image will only take up 235 KB if it is stored at 72 dpi. A 20 x 20 cm image will take up 16f MB at 300 dpi. At 72 dpi, it will be 942 KB, that is less than a megabyte.
Here are the same image sizes in pixel-size:
5 x 5 cm at 300 dpi: 591 x 591 pixels 10 x 10 cm at 300 dpi: 1181 x 1181 pixels 10 x 10 cm at 72 dpi: 283 x 283 pixels 20 x 20 cm at 300 dpi: 2362 x 2362 pixels 20 x 20 cm at 72 dpi: 567 x 567 pixels
For the Rock Art Database, the images should not be wider than the screen, which is most often 800 pixels, the equivalent of ca 28 cm at 72 dpi.