This is my learning log for the OCA Ditigal Photographic Practice course

Saturday, 25 January 2014

Part five–The final image

Project: Finishing

My back-up regime is as follows:
Download image files from my camera’s SD card to an external hard disk drive. My transfer software automatically backs up the files to my “C” drive. All editing is done with the files on the external drive and when the editing and processing is completed, the resulting folders are burned to DVD.
My printing processes have been detailed in previous posts. I am using a basic four colour ink jet printer and the proofing software provided in the Capture NX2/ View NX editing suite.
I find that this provides adequate prints at A4 size.
Sharpening This is something I do very little of, if at all. Sharpening for print is not something I have considered seriously. This exercise will be interesting.
Exercise: Sharpening for print
This is the image that I chose to sharpen and print. The only adjustments I have made are; resize for print, crop and white balance.

Most of my techniques for post processing come from the book Capture NX2 – industrial strength production techniques by Ben Long. I have learned about the Unsharp mask tool  and the following is a description of the process:
The need for sharpening comes about mainly because the High Pass Filter which sits in front of the sensor applies a very slight blurring to the image (necessary for colour calculations) although a lens that does not produce a particularly sharp image when focussed can also be corrected. The principal behind sharpening is to increase the apparent sharpness of the image by making the edges in the image appear more acute. (an edge being a sudden change of contrast made up mostly of light and dark lines). The unsharp mask identifies these lines and increase the lightness and darkness along these lines making the image more contrasty. There are three controls associated with the unsharp mask:
  • Intensity % (the degree of contrast)
  • Radius % (how many pixels of ‘halo’ are created)
  • Threshold (controls how much contrast change is needed before the filter registers an edge  - by pixel brightness value 0-255)
Experimenting with the sliders determined that the ideal radius for this image was no more than 10% and the threshold was left at zero. I produced four different versions of the image as well as the unsharpened one, changing the intensity from zero to 10, 25, 35 and 50%.
Looking carefully at the prints with a magnifier, I found little appreciable difference until the 50% intensity setting. At 0% the skin of the Julie’s face was smooth but the eye detail was less defined. At 35% the eye detail and the skin texture was acceptable so it looks as if this is the ideal setting for this particular image.
Other features of the image the details of the necklace and the fibres in the scarf became more detailed and defined at 50%.
On the monitor, the differences were easier to see. I have added some cropped screen shots below. What is apparent from the screen and not from the print is the ‘halo’ effect. A balance needs to struck between the different areas of the print and it may be that selective sharpening may be required, in this example, on just the eyes, leaving the skin texture smooth

image image
0% intensity
50% intensity
image image

Conclusion: It appears that sharpening has a very subtle effect and may be used to give definition to the most important areas of the image. As illustrated above, selective sharpening could be used to improve just one area of the image. This is a very important tool and each image must be assessed carefully to decide on how much and to which areas of the image needs to be processed to produce a satisfactory print.

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