Analyzing images with semi-transparent blobs


My name is Pavel.
I`m a new imajeJ user whose english is lacking(it is not my native language), so I am stuck not knowing where should I look for info and what keywords should I use for search.

I can express myself reasonably well in English in a trivial conversation, but have no prior experience with image processing, and no knowledge of any jargon(if it exists).

I`ve been handed several images, made with a microscope, that have a lot of semi-transparent blobs in them, along with a scale.
Here is a sample of two different files(they are much bigger than that)

I need to divide these blobs by size in 3 or 4 groups and for each group get the count of blobs with roundness of 0.8 to 1
Then I have to feed this data to a program for Dispersion Analysis.

I have started by performing Spatial Calibration to set actual scale.
Now I can select elliptical shapes and use Analyze -> Measure to find their areas. So I picked a minimum and a maximum area - just for a start.

I then tried to perform Particle Analysis described here
The images are RGB so I tried to set color theshhold but there appears to be no "apply"button.
So after that I used Image :arrow_forward: Type :arrow_forward: 8-bit. menu command and Process -> Binary -> Make Binary
and got this as result:

Then I used Analyze Particles like so:

and got this as result:

Where I should look for what I am doing wrong?
Should I even analyze particles or other things? If yes - how do you call them?

I can look the info up myself, but I`m lacking the vocabulary to perform a search.

Please help!

Sincerely yours,