June 10, 2004


Flatten Illumination using

FFT Low Cut Filtering

(Medium and High Pass Filtering)

Flattening background illumination can also be done in the spatial domain. (See Flatten Illumination exercise).  This exercise illustrates how to do it in the Fourier Domain.

(Image reduced x2 for printing).

For ImageJ, skip this section. Use Process / FFT / Bandpass Filter, as described below.

The center of the FFT should look like this:

Flatten the 512x512 image in ImageJ using Process / FFT / Bandpass Filter,

(Result not shown).  Then use Image / Adjust / Brightness/Contrast / Auto.