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Sharpening

Photos may benefit from a bit of sharpening to enhance the edges in the image and make the subject stand out more.  Examine the close-up from the last page (on the left).

                                  

The features around the face, although more noticeable since we increased the brightness and tweaked the contrast, are still somewhat blurred.  We can enhance the image some by sharpening, in which the computer increases the contrast between adjacent pixels which have different levels, such as the edge between a light and dark area.  I've had the best luck with the Unsharp Mask command (which I've learned from magazines and from other photography websites).  This command applies a small blur and then compares the original image  to the blurred.  If a pixel in the original image is greater than the threshold brightness difference (user set) from the blurred, then the contrast is increased.    The image on the right has been sharpened using the unsharp mask command using a radius (for blurring) of 1, and a threshold (number of brightness level difference between adjacent pixels for sharpening to be applied) of 10, applying at 75% of full effect.

There is not an incredibly large difference between photos, but you can see shadows and edges are more pronounced, and his face has less of a "softened" look that comes with a mild blur.  The effect of the sharpening is muted to some extent by lower resolution set for the monitor display.  Still, the effect comes through.   Sharpening does have its tradeoffs though.  Examine the background and around his temples.  There is a more grainy appearance.  Sharpening can increase the contrast on random noise in the photo, so using this command tends to be a balance between sharpening the image and not filling the photo with noise.  Note that we applied the sharpening after we did the cloning to fix scratches, etc.  If we had sharpened beforehand, the sharpening would have exaggerated the effects of the defects in the photo.

Another example of using Unsharp Mask on a modern photo can be seen here.

So, the final image:

Just to remind you, compare to our original image:

As you can see, digital photo editing can be a powerful tool to restore old images.   We have been working on digital editing of my wife's family photos, and storing them to CDs.  This allows easy distribution of images to family members, and gives us some assurance that the images will be preserved, in case of damage or deterioration of the original photos.

I wanted to make a note about working with the images prior to finishing the section.   You have seen a series of jpeg files (with moderate compression) documenting the restoration of the images.  These jpegs are set for 72 dpi (display on the monitor), and are not set for maximum quality.  I did not want to torture all those people who access the internet via a modem (as I'm doing to upload this site).  The original uncompressed TIFF file is over 5.5 Meg (and if I could have scanned the image it would have been larger) - you would most likely still be downloading the first image if I had this on the site.  Jpeg files are great for the web, but you do not want to use this format for saving files in between steps of working on an image.   The jpeg format compresses file size of images, but it is not a lossless compression.  For a high quality jpeg, the loss is only a small amount, and may not be visible to the naked eye.  But, if you have a jpeg file with a small loss of quality, open and modify it, and save it with a small additional loss in quality, and so on, and so on, the effects of the compression may add up.  My method for dealing with this is to work with TIFF files (they are uncompressed files, big but you don't suffer the quality loss) until I'm finished with the image, and then save it to a jpeg file should I so desire.  So for each step in this tutorial, I have used TIFF files on my machine, and converted the image that I wanted to put on the web from TIFF to JPG.

One final topic I wanted to cover was composite images, on the next page.

 

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