An FFT will transform spatial data ( ie. a picture ) to a spatial frequency domain. This spatial frequency information sort of shows the amounts of detail in the spatial data. Say you had a 64x64 array which was a sine wave as a function of X only, the array would look like a plowed field. And say this plowed field had 5 furrows across it, when you do a FFT you will find that there are dots at F(-5,0) and F(5,0).
MacPhase calculates the FFT, but instead of displaying the data in the real and imaginary forms, MacPhase does an extra step to transform that data to a magnitude and phase form. I think this makes more sense, especially if you are used to seeing diffration patterns in the lab.
Inverse FFT:
Much the same as FFT only it transforms spatial frequency data to spactial data.
Uses for FFT:
Say you wanted to erase that plowed field. By spatial filtering the FFT you can remove those sine wave. Or another example, what if you had a blurry picture, you could decrease the low frequencies and increase the high frequencies intensities.
Convolutions can be done with an FFT by multipling the magnitudes and adding the phases. Then Inverse FFT that result and you will have your convolution. Inorder to center your result you will have to do a Flip-Flop, this is an added step because of the FFT algorithm used.
Color Scanning/Automated Scan:
Color scanning/Automated Scan can help you find hidden detail in a data set.
Making your own apetures:
You can make a few simple apetures using the Filter and Windowing features to help you. For you optics people, you can make abberations which you can subtract out of phase maps. You can also draw apetures in a drawing program, save them as PICT and then read them into MacPhase.
Statistics:
Most times this will show the user what his data looks like statistically, if it does not look right chances are it isn't. Close that statistics window and do a Calc Statistics, then do Statistics again.
Graphics:
Here are some tips for printing graphics: Since MacPhase doesn't spend time removing hidden lines in 3D plots, it is best if you the theta oreintation about where it is, this will allow hidden lines to be removed. Oh, these hidden lines will only be removed when you have either White or Color fill selected. For printing it is best to use white fill, this not only uses less toner but I think it gives a nicer look. If you want to add titles to your graphics you'll have to do that yourself in another program. If you don't have the newest version of the LaserWriter driver, you can save Color contour (gray scale) plots to a PostScript file by selecting the PostScript option in the Text file options dialog.
Clipboard:
You can use MacPhase to copy gray scale images or slices to the clipboard. These can then be imported to other programs or placed into reports. NOTE: For printing of gray scale maps to work while in a word processor, you must have the new LaserWriter driver 6.02.
