In this final blog I would like to share some of the photographic techniques that I found useful in digitally enhancing faint rock art motifs. These can be done on a desktop computer with available software.
The study involved illustration and photography of rock art motifs using colour negative film, digital photography and computer enhancement of faint images. Digital images were enhanced more effectively than colour print images by altering: brightness; contrast; colour balance and saturation. Many of the faint motifs recorded were further enhanced using software to reveal deeper red ochres and outlining that was not visible to the unaided eye.
This is illustrated in the central anthropomorphic ‘reptile-like’ figures at Pym’s Road shelter (see Figures 1, 2). Other faint images in a granite shelter near Palmer show connected anthropomorphic figures that also responded well to this technique (see Figures 3, 4). The digital photo imagery show features in natural daylight and computer colour enhancement of the same motifs. This method can also be used on scratched figures that overlie paintings to show the contrast between the two and the rock patina.
The steps to achieve this on Windows 7 are: Open a daylight digital photograph (preferable taken on an overcast day) in ‘Windows Live Photo Gallery’; adjust exposure (top tool bar on right hand side); click on ‘adjust colour’, displayed will be: Colour Temperature, Tint and Colour Saturation. Hold the mouse over the horizontal adjustment bar and manually drag to the right or left. I usually drag the colour temperature to the right a little, and then the saturation bar almost all the way to the right. You can edit the controls to give a brighter or dimmer view. Then make a copy to save in a safe location.
The comparison between the unaltered and enhanced image will give you a greater depth of ochre colours. The background surface will appear green to blue which contrasts the orange-red motifs at the other end of the colour spectrum.
Another method is to use image enhancing software that can be downloaded for a free trial, such as “Imaging Concept.” This software was developed at Charles Sturt University for medical imaging. It is possible to enhance imagery of Aboriginal rock art with this program by manipulating colour histograms via a look up table (i.e. numbers of pixels in specific colours) it makes it easier for the unaided eye to observe (Faith Coleman pers.comm. 2013).
Figure 1. Faint red ochre figures photographed in daylight at Pym’s Road Shelter.
Figure 2. Same image as above but edited with Windows Live Photo Gallery.
Figure 3. Faint red ochre motifs photographed in daylight in a shelter at Palmer.
Figure 4. Same image as above but edited with Windows Live Photo Gallery.
Good blog and I’m very interested in trying to use the Windows photo editor.
As a side note, dstretch is another similar program and is also free to use. I’ve never had the patience to try using it though!
Hi , came across a couple (well what my totally untrained eye thinks are) sites in Macclesfield , clealand + above mt lofty trail …. mostly rock placements? Rock chipping piles? Some rock carvings? Couple of paintings? Some what appear man dug shelters poss dug for ochre+shelter ? Anyway I’d love too forward what i found to robin ….