Digital cameras generally do very
well in a brightly lit scene, but some 'noise' can creep in for dark
areas or those in which the ISO (equivalent digital 'film speed') has
been increased for low light level conditions. The short
explanation is that in any electrical sensor there is some very small
random signal ('noise') present. For a digital camera image
sensor, dark areas of a photo correspond to very little signal (light)
reaching the sensor. Thus the desired signal is not much
larger than the random 'noise', which can lead to a speckled
appearance. Turning up the ISO setting for a low light level
magnifies this noise. Some higher end cameras have various
techniques for dealing with this, but you can still end up with the
grainy appearance in your photos.
minimizing noise can begin with the exposure settings on your camera,
as discussed in this Expose
(exposing for maximum Signal/Noise -
S/N - ratio by moving the bulk of the histogram
towards the 'right' or higher signal end.
and Paint Shop Pro both have built-in software capabilities for
reducing digital noise, and there are a number of other products on the
market developed specifically for this purpose. Here is
Of Noise Reduction Software
. I have found
Picture Code's Noise
to work very well. Below is an example.
The left pane is the original image, which was badly
underexposed. The second pane shows the result of adjusting
the RGB levels to obtain a better exposure. The exposure and
colors are much improved, but at the cost of a very grainy/speckled
appearance. The third pane shows what Noise Ninja was able to
do for reducing the noise.
of Color For Scanned Photos
very big advantage of digital imaging is being able to archive and
restore old film photos. Once in digital form it will never
fade, and very often much of what was lost can be restored.
Before simply buying the first scanner you find, however, you
should learn a bit about scanning so you do not later have to repeat
what you've done. A
few scan tips
is an excellent resource for getting started.
This resource has been around for awhile, but the basics in
terms of resolution, dynamic range, histograms, etc. have not changed.
is also a very worthwhile read before
Some basic photo editing skills can
easily do a great deal to correct many faded and color shifted
photographs without any additional software. The earlier
these skills are applied in the scanning process, the better the
overall result. However, satisfactory results can often be
obtained by adjusting only in the "post processing" phase of things, if
that is all you have to work with. Here is one Restoration of
Plug-in for Photoshop
which greatly automates the
For an advanced reference,
has loads of good information.
Finally, a good scanner and software can do much right during
the scanning phase. The scans below were made using the Nikon
with the automated Restoration of Color option turned
off (left) and on (right). The image on the left is pretty
much what you see when you hold the slide up to the light.
This same effect can be approximated with the scan on the
left in post processing, but not as well. That is because the
scanner is able to use the full 16-bit depth from the scan sensor to
create the 8-bit final result. When post processing, you are
starting out with an 8-bit image and 'stretching' the more limited
amount of information, which can result in 'banding' and a blotchier
Enhancing Dynamic Range By
a photo with a wide range of lighting can be very difficult, as the
image sensor can only capture a range of lighting levels much lower
than the eye is capable of seeing. For a dynamic, moving
scene there is little you can do about this, but for a stationary scene
you can use a tripod and make multiple shots at various exposures.
Many cameras will allow you to automate this by using an
"auto bracketing" setting, which will quickly and automatically take
multiple shots at a range of exposure settings. If done
correctly, even the lightest and darkest regions will be properly
exposed in at least one of the images. All that remains is to
then combine the correctly exposed portions from each. There
are at least two ways to do this, one of which is a manual method using
layers and masks, and the other is highly automated using special
method does not require any software other than your normal image
editing application, and gives you complete control over the result.
One very good description of this technique is described by Larry
Bracketing and Layers Tutorial
. As the details are
well covered in the tutorial (along with some stunning examples), I
won't say any more about those. Below are two examples of
this method, both of which show the original images as thumbnails,
along with the final result.
Automated Software Method
are a number of automated packages which accomplish essentially the
same thing. One which I have found to be highly effective is Photomatix
not only automates the combination of exposures as seen above, but also
adds a Tone Mapping option. This is additional processing by
the software to enhance local contrast details. The result
can sometimes be surreal, but is often very dramatic. See the
web site for some excellent examples. The image below shows a
comparison of methods for a single image. In this case there
is only one exposure, which is shown on the left. The
exposure is good for the clouds, but all else is underexposed.
It was easy to adjust the levels to obtain proper exposure
for the tree and windsock, but at the cost of losing all sky detail.
The second two images are combinations of the original and
adjusted image. In the layers and masking method, the two
images were placed in separate layers of a single image. The
tree and windsock were 'selected' using Photoshop's selection tools,
and then masking was used to pick which layer was used for the selected
region. This was a slow process, and some small areas where
the selection were not perfect (bright white areas in the tree foliage)
are apparent. The third pane shows the automated result from
Photmatix, with the Tone Mapping option turned on.
Depth of Field Trade off - Aperture vs Diffraction
to Wind Drifter Home
In Macro Photography
is tempting to set the maximum aperture number (minimum diameter opening) to
obtain the maximum Depth of Field, and then blast it with enough flash to get
the correct exposure. However, you may end up gaining depth of field but losing
sharpness if you go too far. That is because of Diffraction
. As the aperture opening becomes very small, diffraction
begins to degrade the image. At what point this happens depends on the sensor
(actually, the individual pixel) size and other factors. However it is easy
enough to determine with your own camera and lens.
The above pic shows a folded text page that was used. The left side was parallel to the lens,
and the right side was folded away from the lens. The lens was focused on the left side. A series
of pics were taken at different aperture settings, and then combined and labeled as shown below. Click
on the image to see the full size result.
Check the full size result carefully. You will see that more of the text on the folded
right portion comes into focus as the aperture (f-stop number) is increased. But also pay
close attention to the 'R' on the left side. The camera is correctly focused for this
region of the page, and it is sharp and clear for all the low f-stop numbers, but begins to
lose sharpness somewhere around f20, and is quite degraded by f45.
Now, none of this means you shouldn't go to the very high aperture numbers if you absolutely
need to get the depth of field, but realize that the depth of field comes at a cost. If you
can get the photo with a lower aperture, then that is the best choice. Do your own tests, and
decide what works best for you.
Depth of Field (DOF) Via Multiple Exposures
photography is relatively
simple for completely flat surfaces. However, for 3D objects
it can become very difficult to get more than just a very small region
into focus. I won't go into the why of that here, as this Depth
of Field Tutorial
Articles and Information
provide a wealth of information on
the topic. I tried several methods of combining multiple
exposures (similar to the Enhancing
method describe above), but with much less
success. This included several different software packages.
I finally found one package that works well and is reasonably
priced. The images below were combined using Helicon
in a mostly automated process. The software
can even adjust for small shifts in the image between frames.
Note: the image below is of a small bit of dried plant matter
of no particular interest in itself. It just happened to be
handy to the microscope when I was looking for something to experiment
There are a number of adapters on
the market which will adapt nearly any camera to a microscope or
telescope. I bought the complete MaxView
This kit has adapters for a variety of telescope and microscopes, and
interfaces to the camera by an additional, special adapter.
To switch to another camera only the adapter for that camera
needs to be bought. There are also many other adapters
available. Here are 3 samples using the MVP kit with a Nikon
5700 camera. The left image is a prepared slide viewed
through a Nikon microscope. The middle photo is of a bee's
eye, made using only the MVP adapter. The right photo of
Saturn was made through a Meade 8" Schmidt-Cassegrain telescope.
Photography - Some Legal Information
In the world since 9/11 many
people have become sensitive to people taking photos in public places.
This can even lead to confrontations with Law Enforcement
personnel who may not be completely familiar with the laws themselves.
I make no claim to offer any legal advice here, however here
are some links that may provide useful information:The
has a down loadable Adobe PDF file which is printable
guide to common photography law, written by a lawyer. It is a
handy guide to print and carry in your camera bag for those times when
you may be accosted by well meaning, but mis-informed individuals.State
by State Privacy Guide
is a compilation of laws by state with
respect to photography and invasion of privacy legal rulings.
Some Processing Tutorials
(updated August 15, 2012)