Hi, I’m looking for a clear definition of ‘image sigma’ (x,y,z) in the Interest Points detection section of BigStitcher. The wiki description (https://imagej.net/BigStitcher_Interest_points) seems ambiguous:
If you chose to Define anisotropy for segmentation in the previous dialog, you will be asked for Image sigmas in X, Y and Z here. If you acquired your images with pixel sizes and z-spacing of (optimal sampling) with being the resolution of you microscope ( and ), you can leave the default value of 0.5 here. Otherwise, increase the image sigma when you have oversampling (smaller pixel distances) or decrease it for undersampling (larger pixels).
Since the default values in the fields are 0.5 one would interpret it as the ratio of pixel size over microscope resolution (the Nyquist criterion being a ratio <= 0.5). However this interpretation seems to be in conflict with the two examples set forth in the wiki, whereby with oversampling the sigma would increase and with undersampling decrease. On the contrary oversampling would imply smaller pixel size and thus smaller sigma.