This isn't intended to be a detailed technical description of why grain anti-aliasing is an issue, its an introduction and an overview of how we overcome the problem.

Grain anti-aliasing is one of the main reasons why high quality scans sometimes disappoint (compared with traditional prints or slide projections). It happens with scans from any source, but is more pronounced with a small original such as a 35mm slide than with a 5x4. Good scanners, particularly operating at high resolutions, can sometimes produce a 'grainy' effect. So that smooth pale blue sky begins to look granular; rather being a single colour it begins to look like a mosaic.

Along with dust and scanner noise grain is the third thing we wake at night worrying about.

You'd expect a scanner that out resolves your camera (as ours do) would produce a better scan. So why does this happen? First, at high resolution a digital scanner begins to see the difference between the individual grains that make up the surface emulsion. You get a data value not just for the grain but also for the bit of emulsion in between. Instead of a stream of pale blue data you get a lot of pale blues, plus some others.

Second, a slide projector or an optical enlarger flatters and this can help an image. The individual light path that transmits pale blue overlaps slightly with its neighbours, thus contributing to the smoothness of the blue.

With top flight scanners grain anti-aliasing means more can be less. You expect a better scan than the print you got from a High Street print shop, but no, it looks worse. Crazy? Yes, but you can't avoid the problem.

We decided to do something about it. We found very clever software which will look at each image and identify the tell-tale signs of grain. Each scan is examined and using advanced mathematics a set of corrections is applied. The result is better smooth tones in open areas (sky, solid blocks of colour, shadows) and better detail. This process also reduces scanner noise at the same time.

It naturally takes time as each scan has to be reprocessed, a computer intensive task, but the results are worthwhile. We can now offer our discerning clients the top quality images they demand.

Questions?
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01277 222 398 or 07960 325 207.

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