by Mike McNamee Published 01/04/2013
Having successfully installed one wall with bespoke wallpaper, we became curious about the other options that were available especially those from Epson. We had seen the giant SC-70600 at photokina; at 64-inch throat it is an impressive machine. The gamut should be equally large as it has C M Y K Lc Lm Lk O inks along with white and matt black. The offer for a play on the thing was too tempting and so plans were hatched to make a wall-covering for Gallagher's new office.
This article looks in some depth at the requirements and methods for making and preparing the massive files required for wall covering jobs.
The Size Problem
For many wall paper applications the minimum resolution is set at 72ppi. Presently the largest file size available from a 35mm footprint DSLR is that of the Nikon D800. This delivers a 103MB file which is 7,360 x 4912 pixels and represents an image of 102" x 68" at 72ppi. Now a typical wallpaper drop is around 72 inches (by 21 inches wide) so our D800 looks good for about five drops. We now rely on 'interpolating' the image up to the required printing resolution which is a goodly fraction of the 1,440 dpi the print head works at and is normally preferred in the range 300 to 360ppi. Thus we require an interpolation of about fivefold (72 to 360) to get our image ready for printing. The subject of interpolation is complex and gets its own sub-section later but for the moment let's consider the ways and means of providing more pixels at the shooting stage of the operation. There are a number of reasons to need interpolation or expansion and the mismatch between the aspect ratio of the image and wall area is one of the key factors.
The aspect ratio of the wall is a critical parameter which, unless the wall has a ratio of 4:3, always degrades the number of pure pixels available. By way of example, Paul Gallagher's wall, featured here, is almost square and thus loses almost 30% of the pixels right off! When considering the choice of file therefore the aspect ratio of the wall to be covered should be the first thing you calculate.
This is not interpolation, this is devising ways of adding to the image size with pure, thoroughbred non-interpolated pixels. There are a number of ways.
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