Take an image that you have processed as the reference standard, with some edge detail and some smooth areas. A portrait is ideal – with the eyes carrying wanted detail, and the skin smooth areas that you do not want to be over-sharpened. For the reference image, make sure that you have applied no software sharpening.
Now make three more versions, each with a different degree of sharpening. There will be a certain amount of trial and error in this, but make sure that the weakest of the three is quiet close in on-screen appearance to the unsharpened original, and that the strongest is noticeably aggressive.
Print all four (unsharpened original plus three differently sharpened versions) at full size. Next, with neutral white lighting next to the computer screen, compare these prints with each other and with the 100% magnification images on-screen. You may be surprised at the difference in appearance between the same images as it looks on the screen and as a print. Use a magnifying glass to inspect the prints in detail.
Write down the difference you see, and also your assessment of which degree of sharpening seems to your taste to be the most appropriate for the image in print form. Note the results in your learning log.
I have made a couple of changes to the requirement of this exercise. I was not able to find an ideal portrait shot as suggested above, so, looking through my image bank I came across a photo, taken during the summer, while I visited a county show close to my hometown in the UK.
My decision to use this image of an owl was because of the detail contained within it’s plumage, which although is already quiet sharp, I thought it could be improved upon so that the birds head really stood out within the frame.
Aperture Priority; Shutter Speed 1/500; Aperture f5; Focal Length 78mm; ISO 400; Spot Metering; Auto White Balance
As you can see in the original image, this is an already bright and well-focused shot, with the blur as it should be, in the crowded background, with our full attention focused on the owl.
Upon closer inspection, detail around the beak, where the hair is finest, is quiet blurred and fuzzy, so this is where I wanted to improve the shot and bring out the highlights all around the face.
Opening my image in Adobe Camera RAW, I controlled the clipping and lightened the blacks just slightly, and then went into the details feature and made a minor adjustment to the noise by increasing the luminance slider a fraction. Upon completing this work, I opened the image in Photoshop.
I went into the unsharp mask filter, to look at the details of my original image, which read; Amount 36%, Radius 0.1 Pixel(s) and Threshold 10; these would be my benchmark readings.
Making my first copy, using the unsharp mask filter, I left the threshold at 10 and on the advice given by the various literature I had read and watched during my research, increased the radius to 1-pixel. Doing this allowed for sharpening within the fine detail, my aim for this exercise, I then changed the amount to 50%. Doing this met with the exercise requirement of there being little change between the original image and my first sharpening filter.
As you can see, there is very little change between these two images, although a small amount of brightening is present around the eyes.
Next, I copied this image and set about my second pass with the unsharp mask filter where I left both the threshold and radius unchanged, but moved the amount up to 200%, which has greatly improved the shot by continuing to brighten some of the finer feathers around both the eyes and mouth.
When comparing this image to the previous one, the definition around the eyes is beginning to make them really stand out even though the lightness around them has not changed too much.
For my final image, I duplicated this image, and as before left both the threshold and radius the same, but cranked up the amount to 500%, the highest value allowed by the slider.
Here we can see the biggest change of all, especially in comparison to the original shot. The eyes really pop now, and the brightness has migrated down to beneath the beak and onto the breast making the individual strands stand out more, thus giving the impression of improved sharpness. The difference between these four images can be seen below, where each image has been cropped tighter to highlight the owl’s face.
For this part of the exercise, we are required to print our images and compare them with their on-screen counterpart. I have done this, but my printer here is not as good as the one in the UK, so I have muddled on as best I can.
Looking at the cropped images above and comparing them with their printed counterpart, I actually feel that the images look better on the computer compared to those in print (the printed images can be found in my sketchbook), but I feel that this is down to both the quality of printer and paper used during the exercise. On screen, all of the images look vibrant and almost lifelike, but in print, the images are a little dull in comparison, although on closer inspection the printed images, especially the final two are very crisp and the detail well contained.
I feel that this level of ‘high-end’ sharpening has a place, and this place should be centred on subject matter and viewing arrangements. Even though I really like the last image produced with the highest level of sharpening, I think image three, sharpened at 200% is the nicer shot as it appears more in kin to the bird in real life than the over sharpened image.
As with most of the exercises conducted during DPP, this has been very interesting and quiet enlightening. I have always thought that the images I choose to share are in the sharpest focus that I can produce, but now I see that with a few minor tweaks, images can be perceived as being even sharper and more detailed within their frame.
It continues to amaze me how much light can influence our images, yes, I know that photography is all about light and they way we capture it, but who would have thought that by changing the brightness of a shot it can actually make it appear sharper? I am looking forward to adding the unsharp mask filter to my post-processing workflow, as I can see this will be a handy tool to master in the future.
I continue to learn that using Photoshop to improve my images is not such a bad thing, as long as I am true to my beliefs and do not cross any ethical boundaries. An odd tweak here and a minor alteration there is okay, but that should be where the line is drawn.
Cambridge in Colour. (n.d.) Guide to Image Sharpening [online article]. Available at: http://www.cambridgeincolour.com/tutorials/image-sharpening.htm [Accessed 8 November 2013].
Walsh, J. (2010) Photoshop CS5: Michigan’s MI Learning, 0902 PS CS5 (Unsharpen Mask) [iTunes U podcast]. Available from the iTunes store.