Street Photography Magazine

correction built into their firmware that often

causes interpolation errors. Image noise can

also cause color errors, and brightly lit objects

can produce fringing due to oversaturation.

The image sensor itself can also be the

source of fringing effects, due to smearing or

blooming. Blooming often occurs in older

cameras that are equipped with CCD sensors,

especially if used to shoot a bright subject

(such as the sun) using a wide aperture. Newer

cameras with CMOS sensors are less sensitive

to this type of error.

Color errors and ghosting can also occur

if you photograph a brightly lit subject using

a poor-quality lens. It is often quite tricky to

differentiate between the exact causes of

these types of effects.

Software Filters

are a Proven Solution

Chromatic aberrations are some of the more

irritating image errors that can occur, and are

obvious even to the untrained eye. They occur

regularly in various forms, even if you have

invested a lot in high-end equipment.

Software filters are a proven way to take

the edge off lateral aberrations, whereas axial

aberrations are more difficult to correct

digitally. As for all other types of lens errors,

chromatic aberrations cannot be completely

eliminated, even using the most sophisticated

tools, so it is essential to use the best lenses

you can and appropriate shooting techniques

to keep them to a minimum.

An accepted way to prevent axial

aberrations from occurring is to use

the optimum aperture. This is the

smallest aperture at which your lens

produces its best sharpness. The

optimum aperture depends on a

series of variables and can be quite

complicated to determine. Generally

speaking, it will be somewhere

between f8 and f11 for a conventional

DSLR, although the precise value will

vary from lens to lens. Other systems,

such as Micro Four Thirds, have

greater overall depth of field than DX

or full-frame cameras and are thus

less prone to chromatic aberrations.

The only reliable way to determine

the optimum aperture for your

particular setup is to subject it to a

controlled lens test.

Optimum Aperture

Typical axial aberrations: only the

branches in the foreground show a

magenta cast and ghost-like ‘doubles’.

The trees in the distant background are

not affected.

Image: Thomas Saur

Axial aberrations
occur when the
images formed by the
individual color
channels focus at
different places along
the optical axis of the
lens. The effect is
particularly evident
at wide apertures
and results in
fringing and
psychedelic-looking
double images.