Problems with ImageJ 1.53 analyse particles on MacOs Catalina (10.15)

Hi all,
I am trying to use the analyse particles function of ImageJ on a MacOs Catalina computer. The idea is that I want to count a number of fluorescent cells in a brain slice, and determine their localisation. I have done this in the past many times (MacOs Majova was the last software, using ImageJ 1.52a), always successful.
What I do is the following: I have a tiff with the fluorescent cells, convert this to an 8-bit image and set the threshold by hand and press apply. Then I use the analyse particle function, where I usually have to adjust the pixel size to not take every small pixel along in the analysis, but only the actual cells. However, now with Catalina and ImageJ 1.53, upon analyse particles, the program does not see any, or only very few cells, whereas in picture I see with the threshold many cells. Exact same settings (threshold, analyse particles, etc) on the previous computer works perfectly fine and gives me many cells counted.

Do you have any idea what goes wrong here?

Thanks in advance!

Just a wild guess but I once had a problem with area-filtering in pixel instead of µm² units. The area threshold of course differs drastically between the two settings. Maybe the standard setting is different between your two Macs?


Dear Joachim,
Thank you for your suggestion. In my version of ImageJ, I do not have that option, to change between um or pixel, it is actually always set on pixel.