Nikon D300 Complete Manual page 62

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The anti-aliasing filter (top gray layer) filters out high frequency

detail and near infrared energy in the light (orange arrow) before it

gets to the microlenses that sit over the photosites (Bayer pattern

Why is the filter called a "low-pass" filter? Artifacts—

unwanted data—are produced by any analog-to-digital

conversion. There's a basic rule of conversion that all input

frequencies below something called the Nyquist frequency

will be correctly produced, while those above the frequency

tend to more easily generate aliasing artifacts (often visible

as moiré or color fringing in digital cameras). The filter on

the D300's sensor attempts to pass the data below the

Nyquist frequency for the sensor pitch, and reject data

above that frequency, thus the name "low-pass."

The IR-cut and anti-aliasing filter can be removed from

some cameras (with a great deal of fussy disassembly that

will void your camera's warranty). Why would you want to

do that? Two reasons: (1) By removing this filter you

remove all the anti-aliasing. This can produce higher acuity,

but at the potential expense of more incidence of moire and

aliasing of diagonal edges. (2) By removing the IR-cut

filtration and substituting a visible light-cut filter you can

convert a camera into a dedicated infrared camera (see

"Infrared" on page <687>). Unfortunately, the D300 design

has a complex filtration design due to the automatic sensor

cleaning system. After disassembling a D300, I can see that

it is not going to be easy to circumvent the filtration or

replace it, and you'd likely lose the special sensor cleaning

Thom Hogan's Complete Guide to the Nikon D300

Troubleshooting