A complex subject.
Jpegs made by a camera are already sharpened and most users would not feel
they need additional sharpening, which can introduce many artifacts.
RAW digital images and scanned film require sharpening for best results,
either print or video/web display.
How much sharpening is an aesthetic as well as technical choice.
The ubiquitous unsharp mask is a good tool for sharpening. If you have
recent Elements/Photoshop the Smart Sharpen tool is more flexible.
There are many books and web based tutorials that cover the subject better
than an answer here.
Sarath <CSarath@gmail.com> wrote:
>Dear All,
>
>I am a beginner in photography.
>
>Actually is it really required to sharpen every image? Also heard the
Yes, virtually every image will be improved by at least
some sharpening (the grain structure with film
accomplishes the same effect but is very hard to
manipulate, while that is easyr to do with digital).
>cameras have built in capability to sharpen image to an extend.
If the camera produces JPEG images they are almost
certain to have some sharpening done. Most cameras
offer optional amounts of sharpening, but the problem is
that how much is correct depends on such things as the
size of the displayed image and the subject matter,
which makes it very difficult to correctly choose
sharpening in the camera. Generally the camera is
probably best set for minimum sharpening (because it
cannot be removed), and if it is useful extra sharpening
can be added later.
If you shoot RAW or to a format like TIFF, it is not
sharpened by the camera.
>When I done a small search, it is found that Unsharp Mask technique is
>widely used for sharpening image. Why people selects that?
USM, or UnSharpMask, is *not* the same as "Sharpening".
It does have a similar effect on the image though,
making it appear overall to be "sharper".
Both USM and Sharpening can be applied with good effect
to many images. USM should probably be done first.
Most people agree that Sharpening is just about the last
thing done before an image is printed or otherwise
displayed.
>Could you please give more info on Sharpening an image?
Go back to Google, and do more searches! There are many
many web pages with descriptions and examples that go to
any technical depth you wish, and almost any of them
will be much better than any text description which can
be supplied on Usenet.
--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@apaflo.com
Sarath <CSarath@gmail.com> writes:
> Actually is it really required to sharpen every image?
Yes. Without sharpening, digital images look soft and dull.
> Also heard the cameras have built in capability to sharpen image
> to an extent.
Correct. If you shoot JPEG, the camera will by default sharpen
the image for you. More advanced models let you select the amount
of sharpening to apply in-camera, but all JPEGs are sharpened
in-camera. If you shoot RAW, you are expected to apply the
sharpening yourself.
> When I done a small search, it is found that Unsharp Mask technique
> is widely used for sharpening image. Why people selects that?
Because the so-called "unsharp mask" (USM) technique is widely
available and simple to use as a ready-to-use filter in most image
editing programs. There are other sharpening techniques in use, but
they require more work and skill.
The USM digital filters that people now use was adapted from a
technique that originated with film. The origins of the technique,
and how to best simulate the original in Photoshop (i.e. without
using the built-in USM filter) is explained here:
"Sarath" <CSarath@gmail.com> wrote in message
news:1188434014.042391.161740@m37g2000prh.googlegr oups.com...
> Dear All,
>
> I am a beginner in photography.
>
> Actually is it really required to sharpen every image? Also heard the
> cameras have built in capability to sharpen image to an extend.
>
> When I done a small search, it is found that Unsharp Mask technique is
> widely used for sharpening image. Why people selects that?
>
> Could you please give more info on Sharpening an image?
>
> Regards,
> Sarath
>
Sharpening depends on the image. Due to the way the data from the sensor is
processed, the image is a bit soft looking, so most cameras sharpen the
image by default. I find that some cameras over use this and the images look
overprocessed or have video like appearance. Some cameras allow you to turn
sharpening down and you can do sharpening in your photo editing software.
You may find that you can do a much better job than the camera. Learn how
the various settings affect the image when using the USM (UnSharp Mask) tool
by practicing on an image.
One problem I found with the newer high resolution point and shoot cameras
is the image is noisier and the camera has to apply noise reduction to
remove it. The noise reduction is not as effective along the edge of
differering contrast in the image (Like the edge of a persons face). When
you try to sharpen an image like this, it makes the edges have a bumpy
appearance.
> Dear All,
>
> I am a beginner in photography.
>
> Actually is it really required to sharpen every image?
No. It depends on the aesthetics of the individual image. Most people
sharpen images pretty much as a reflex action, but some images look better
if they are softer rather than sharper - indeed some classic images have
the subject totally out of focus, albeit perhaps against a sharp
background. This can lend an air of mystery, romance, or even dynamism if
the subject appears to be moving. Try experimenting with sharpening just
some aspect of an image, e.g. the eyes in a portrait. Sharp details will
help focus attention on that part of the image.
> When I done a small search, it is found that Unsharp Mask technique is
> widely used for sharpening image. Why people selects that?
Unsharp mask is useful because it does not indiscriminately sharpen
everything (e.g. image noise). Instead by choosing a suitable pixel radius,
you can sharpen detail of a particular scale without sharpening very fine
detail which is probably just noise. It is not perfect, but it can be
better then simply using a normal sharpening tool. You should experiment
with different methods and see which gives the best result for each image.
Sharpening is also related to how the image is viewed. When printing a
picture, the resolution will usually be much higher (e.g. 300dpi) than when
viewing it on a computer monitor (typically 100dpi). If you are going to
sharpen an image, then you will want to sharpen it more if printing it out
on paper than you would for viewing 1:1 on your monitor, otherwise the
effect will be too subtle to notice.
Sharpening Really required? 
Linear Mode
