Page 309 - Friedman Archives

Lens Comp. 309

6.29.2 CHROMATIC ABERRATION
The next setting usually occurs only
in telephoto lenses. As you know,
optics are designed to bend light.
And as you also may know, optics
might also have the ability to bend
light like a prism does – that is,
different wavelengths get bent by
different amounts (Figure 6-25). To
combat this, many expensive
telephoto lenses employ something
called “apochromatic” glass which is
designed to bend visible wavelengths Figure 6-25: Chromatic Aberration is
by the same amount, resulting in very what happens when the optics don’t
sharp pictures at long focal lengths. bend all wavelengths of light by the
The good news is that if you same degree. Usually this effects
understand the lens characteristics telephoto lenses above 200 mm.
extremely well, you can compensate
for this in the camera.
Sony’s Chro. Aber. Function is designed to combat this characteristic. And
I can think of no good reason to ever turn this feature off.

6.29.3 DISTORTION

The third lens correction is formally referred to as either “Pincushion
Distortion” or “Barrel Distortion” (but Sony likes to just call it
“Distortion”). Essentially it means that a lens will start to curve straight
lines at different focal lengths. (See an example in Figure 6-26.) If you
understand the characteristics of a specific lens (at each focal length) you
can correct for it in-camera, which is what the Distortion Comp. mode does
when it’s set to AUTO. Like the other lens correction functions, I can think
of no good reason to turn this feature off. (Ever.)