articles/Nature/verysharppractice-page5

Very Sharp Practice - part 5 of 1 2 3 4 5 6

by Mike McNamee Published 01/06/2010

Test 2
Test 1 showed some flaws in our experiment so we went back and re-organised the tests. This time we applied the three levels of presharpening followed by Martin Evening's recommendations for 'inkjet post-sharpening'. This was carried out using the values and methods from the PixelGenius software but we wrote our own action script to carry it out. A matrix of 12 images was made using three levels of presharpening and four opacity levels of 'PixelGenius' sharpening (see callout box). These were then presented to our viewing group.

RESULTS
To test the sharpening levels we again consulted a group of experienced photographers, showed them a matrix of images and asked them to vote for their preferred choice. Although they were unaware of the settings, they were in fact three levels of presharpening followed by the PixelGenius settings for pre-printing sharpening but presented at layer opacity levels of 0%, 30%, 66% and 100%. The viewers showed a preference for the images with IDs 5 and 6. That is higher pre-sharpening than Martin Evening but lower opacity on the High Pass Layer (ie 30% preferred to the nominal 60% specified by Martin Evening).

One interesting interpretation of the result is that the viewer's sensitivity to the overall level is quite mild (ie insensitive). Note that on paper, bumping the Amount from 80 to 150 and the Radius from 1.0 to 1.5 may seem a lot, but both received similar preference scores. In both cases, the image looked over-sharpened at 300% zoom view but had obviously turned out about right in print.

A question that arose from this finding was just how much sharpening is being applied by the photographers who enter competitions with massively over-sharpened images and why they do so? Should they be wearing spectacles (or if they already do should they be using their 'readers' rather than their varifocals)?

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