Paddle steamer captains’ river navigational chart

The Barka / Darling is one of the longest rivers in Australia, wandering from its source near Brewarrina and Bourke in north-west New South Wales across roughly 1500 kilometres of mostly flat plains to meet the Dhungala / Murray in the south at Wentworth.

Object No. 86/1251 is a navigation chart, or river map, that was drawn and used by Australian paddle steamer captains on the Barka / Darling River in New South Wales between 1870 and 1890. The river’s course, landmarks, woolsheds, hotels and homesteads from Menindee to Wentworth were hand drawn on the chart in iron gall ink with notes about rocks and dangerous river sections.

— Powerhouse Museum, 2024

Capturing a 39-metre almost-2D object, a metre at a time

When the Powerhouse digitisation team began capturing the entire map as a digital object, an early decision was to unroll and shoot one metre at a time on the floor of a studio. The images of each section would then be ‘stitched’ in sequence during digital post-production to create a single long scroll. The team also chose not to flatten it beneath glass, as that risked damaging the map.

Working with a team of conservators, photographer Linda Warlond gently unrolled the object to reveal just over a metre for each shot and positioned its bottom edge as straight as possible against reference markers on a backdrop.

The digitisation team allowed 100 mm extra map length either side of the metre to give the postproduction team some overlap during the image stitching and included a Macbeth Chart for colour calibration at the edge of each frame. Warlond also set up copy lighting from each side, which provides flat, even illumination over the whole object:

‘Each frame, each section, we’d light meter all four corners as well as the centre to make sure there was even distribution of light,’ says Warlond. ‘You don't want one stop of light difference between any point because you'll end up with a vignette effect. And when you’re stitching those images together you’d get those vignettes joining up.’

With the camera locked in place on an overhead rig, Warlond systematically captured all 39 metres on a digital SLR camera using a 50 mm lens in a little over an hour.

‘I shot it at f/16 and ISO 100, the native ISO speed of the camera, to make sure everything was in focus and we captured as much detail as possible,’ she notes. ‘Every image was named in the order it was shot, otherwise you would really struggle to put them all together in post-production, with so many long snaking curves in the river. It really is just being methodical, the process of it, and to avoid damage we only wanted to handle it once.’

‘It broke the jpeg image limit’

— Powerhouse Museum, 2024