[filmscanners] Re: PS sharpening

["Julian Vrieslander" <julianv@mindspring.com>]

On 8/7/02 12:55 PM, "Alex Zabrovsky" <alexz@zoran.co.il> wrote:

> I would be interested to know how people use Unsharp Mask in PS to make the
> images sharper, especially following high settings of GEM (produced by Nikon
> IV ED)
> I'm still trying to establish the range of best Unsharp Mask settings for
> different cases (scenic, portraiture and other kinds).
> Let's assume the scanning resolution is 2900 dpi  and 1000 dpi.

My workflow usually goes as follows

1) Sharpening is not done until after all other image manipulations are made
in Photoshop, at original scan resolution.

2) Set "Image > Image size" to final desired size and resolution.

3) Set "Image > Mode" to "Lab Color" and select Lightness channel.  Image
now appears in greyscale on screen.

4) Set image magnification to 50% or 100%.

5) Bring up "Filter > Sharpen > Unsharp mask" and set params as follows:

Amount = 125%

Radius = dpi/200.  For example: if image is set to 240dpi for inkjet
printing, the radius is set to 1.2 pixels.

Threshold = 0 to 8.  Use the higher values if the film is grainy, or when
you do not want the sharpening to emphasize skin texture in portraits, etc.

These recommendations are only starting points.  Vary the params and look at
the effects.  The optimum values will depend on the image, the properties of
the output display media, and your own experiences/preferences,

6) Set "Image > Mode" back to "RGB".  Save or print the file.  You may want
to keep another copy of the file in unsharpened state at original
resolution.  You might need different sharpening settings when the image is
used for another purpose or set to a different size and resolution.

The above method applies sharpening only in the luminosity (lightness)
channel, which reduces color-changing artifacts.  You can get the same
effect by sharpening in RGB mode, then immediately selecting "Edit > Fade
Unsharp Mask" and choosing Luminosity from the popup menu.  But I find it
easier to choose the optimum sharpening effect when viewing the image in
greyscale.

There are many ways to sharpen.  Bruce Fraser's articles (mentioned in
another message) are worth reading.  You can find many more tutorials on the
net with other good ideas.  The best advice is not to over-do it.  If you
see thin light halos around dark edges, you have applied too much
sharpening.

--
Julian Vrieslander <julianv@mindspring.com>

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