Photography Problems

These problems relate to digital imaging in general, whether photographed or scanned.
The examples here are from a copper plate print of Stonehenge scanned at  2321 x 1646 pixels.
Note the 'banding' in the area of clear sky toward the top-right of the picture.
This is the optical interference between the reduced picture resolution and your display monitor resolution.
As the image is enlarged (Fig 2 and Fig 3) the composition lines become more distinct and the interference banding is reduced.
The banding problem is acute on prints with a lot of clear sky or still water, and maps that have a lot of hatched sea around coasts.

Fig 1 Display picture 500 x 355 pixels The individual lines that generate the sky's detail are not visible, but their presense is interfering with the horizontal lines generated by the camera at the time of taking.
Fig 2a Section of sky from 1000 x 709 pixels version. Picture lines are now visible, and the problem has been reduced.
Fig 2b Section of sky from 1000 x 709 pixels version. As above, but  skewed by 2 degrees. Note the vertical bands caused by the interference of the 2 degree lines of the print and the 0 degree lines of your monitor.. With the side-bar move this image up and down and observe the columns of interference marked by the arrows.
Fig 3 Section of sky from 2321 x 1646 pixels version. This shows the lines from the engraving in greater detail. Note the spacing of the lines does not hint at the banding shown in Fig 1.

A Past Pages Information page      www.pastpages.co.uk              Tony Nicholls  2008