Very Sharp Practice

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Don't Try This Unless You Are Serious!

Test 1
The first test was to pre-sharpen in Adobe Camera RAW – only. This is an attractive proposition for a busy photographer as the sharpening is applied once only and can be applied to all images in a set or folder. It has the advantage also of being reversible as it is applied to a RAW file. The workflow is akin to shooting JPEG and passing the files right off to press or to album printing. Martin Evening has published settings as shown below.

We took the 'detail' settings as being appropriate for the bird subject and applied them at progressively stronger and stronger values before making a composite print without performing any interpolation. This was then printed at 360ppi using 2880dpi, High Speed off and Max Detail on an Epson 3800 printer, ie the best conditions we could muster. The composite print was then presented to 50 photographers experienced at viewing prints, and they were asked to vote which was the 'most pleasing' level of sharpening. In addition, the print set included a further group of images sharpened using the default 'detail' settings but with varying levels of Clarity applied in ACR

Only one out of the 50 went for the unsharpened image, the remainder went, in rising numbers, for the pre-sharpened values (without any Clarity), in rising order of strength. The highest vote was gained by values of 150 Amount, 1.5 Radius and 80 Detail. As the graph shows, the graph did not tip over into 'over-sharpened' territory, a flaw in the experiment. We expected Clarity to influence the result because negative Clarity softens an image and positive Clarity seems to produce an apparent increase in sharpness – it increases mid-tone contrast. Our viewers were not fooled! Any amount of Clarity drew a few more votes over the baseline, but not a significant jump. This was unexpected, but statistics do not lie (really?).
 

 

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)?

At the time of writing, this is looking like a topic that will run and run, we do not anticipate having seen the end of it yet! If you are bugged by a sense that you are not as sharp as you might be, start with the values from samples 5 or 6 in the table then print a few shots with opacities ranging from say 20% through to 80% and take a look at real, full-size prints. Once you decide on some values, write an action and run with it for a period of time and see how you get on – modify only on the basis of looking at prints.

 
 

 

 

Sharpening for the web
All that has been written on the previous pages has little bearing on preparing images for digitally projected competitions or website use. Here we defer to the work carried out by Italian professional wildlife photographer, Juza (see www.juzaphoto.com). Juza keeps a website populated with images of superb technical quality, especially in regard to their sharpening. He also details his preferred workflow for creating web images. It is a two-stage process, stepping down from camera resolution to 2,400 pixels and then to 1,200 pixels with inter-stage Smart Sharpening.

We modified his methods in line with a desire to end up with a 1,400 pixel image for digital competition. We presharpened in RAW as before, then reduced the scale to 2,800 pixels using Bicubic Sharper as the interpolation method. We then sharpened using Smart Sharpen (see table) followed by another reduction to 1,400 pixels and a lower level of Smart Sharpen. This was followed by a 'Save for Web' routine to create a JPEG file, tagged with an sRGB profile. This final file was then compared with a RAW pre-sharpened file that was scaled directly to 1,400 pixels using Bicubic Sharper. The screen grab below indicates the results – which were visible on the monitor, but might not show up in print.

 

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