Words of Wisdom - Ron Cork

Simon Galbally discusses some of the key comments made by Ron Cork whilst judging images in the April 2009 MCC EDI Competition.


The judging last week by Ron Cork highlighted a few important reminders for both digital camera users and film/scan shooters alike. The three key points he raised, and which somewhat dominated his judging comments, were those most often overlooked when we prepare images for both projection and printing alike:

  1. Sharpness - sharpening (as opposed to focus);
  2. Focus - image sharpness and depth of field;
  3. Size - the limitations of file sizes.

He further highlighted how contrast, colour depth and techniques such as dodge and burn as well as vignetting can enhance an image's impact - optimising how we can better communicate what we are seeing and want to convey to others.


He provided us with an excellent demonstration of these factors using a collection of images. Often our camera files and film scans only appear their best after even minor "tweaking" of contrast, colour saturation and sharpening.


Firstly, with regard to sharpness, he reminded us that as a matter of physics, digital sensors and scanners alike do not natively produce truly "sharp" image files. Post-processing is essential to getting the best from what our cameras or scanned film captured. The use of the Unsharp Mask is an essential tool; but, as he demonstrated, an essential tool to be used with great care. An over-sharpened image becomes quite ugly to the viewer.


A good tip to keep in mind when applying the Unsharp Mask to an image is to look for artefacts and if the amount of Unsharp Mask required is causing a rather unnatural look then you have applied too much. This means the image was out of focus in the first place or you have oversized the image beyond the amount of data in the file.


Secondly, he reminded us about where certain types of images require critical focusing to avoid disappointment. Critical focusing is the single critical point at which the lens must be 100% in focus - such as a person's eye or a flower's stamen.


An important tip for those of us using auto-focus lenses is to never assume that the lens focus points will always focus at the exact point we think it has (in my own opinion this is where multi-point AF lenses can be a hindrance and on many occasions we are well advised to revert to a single point focus setting).


Furthermore, the use of depth of field and "selective" depth of field can greatly enhance an image. Depth of field ensures sharp focus from foreground to background, letting the composition and scene "tell the story", whereas "selective" depth of field (a great feature of tilt and shift lenses and large format cameras) helps to eliminate distractions while providing an understanding of the object's context.


Finally, he pointed out the risks of degrading images by over-enlarging them - for EDI and prints alike.  Here we must be mindful of the image file size (for both digital camera files and scanned film files). The amount of data limits the enlargement size and this has not changed since film. Like film, the various digital camera formats and sensor resolution (data file size) limit the practical print and EDI image sizes. To over-enlarge digital files, like film frame sizes, risks creating unattractive images. Worse still it encourages us to try to compensate by over-sharpening the images, which simply exaggerates the problem.


So, we are well advised to understand our cameras' (digital and film) image enlarging capabilities. Those of us who grew up with film understand why many owned 35mm cameras and medium format cameras - providing vastly different image enlargement opportunities and limitations while maintaining their very best image quality. The lesson is not to push our equipment beyond its intended capabilities, that way we will project or print optimal quality images even if a bit smaller than we'd ideally like!