- Convert JPEGs to TIFFs (16 bit preferred) and only resave as JPEGs once you are
done editing your image and ready to send to the microstock library. - Don’t repeat save JPEGs as this causes cumulative image degradation.
Chromatic Aberrations
Called CA for short, chromatic aberrations are color fringing on edges
in images caused by lenses not focusing different wavelengths accu-
rately on the sensor. The microstocks are sharp on too much CA, so
check your pictures, particularly the edges of the frames, for this
problem.
Take a look at Figure 5.12A and the cropped section indicated in
red. Figure 5.12B illustrates a cropped section showing fairly bad edge-
of-frame CA; notice the color fringing at the areas of high contrast.
Figure 5.12C shows the corrected version.
If you shoot raw, then your raw fi le converter may include the
facility to remove or reduce CA before decoding the fi le. The built-in
raw converter with Photoshop CS3 has just such a facility. If not, or
if you shot the photo in JPEG, then you can still remove CA by judi-
cious application of Photoshop’s Lens Correction fi lter (Filter > Distort
Lens Correction). I used the built-in CA-removal tool with my stan-
dard raw converter, Silkypix, on Figure 5.12B.
Moiré and Color Noise
Moiré is similar to the color aliasing normally visible on fi ne detail as
the limits of the sensor’s resolution are reached. It manifests itself as
ABC
FIGURE 5.12A–C A illustrates buildings
and cutouts. B and C show before and after
shots of chromatic aberration.MOIRÉ AND COLOR NOISE 93