Small Nanoparticles that are not well-defined - TEM images

Hello,

I’m new to image analysis and I have been having some challenges with processing some images in Fiji. I have some metal carbide nanoparticles (~2-3 nm in diameter) on a carbon support grid TEM images.

I want to analyze the size and shape factors (e.g. roundness or circularity) of those nanoparticles.

The issue is that the nanoparticles are not well-defined and getting a proper contrast between the nanoparticle and the background is difficult.

I tried to start with background subtraction and setting a threshold, then adjust the contrast, but I cant seem to get the nanoparticles distinguished from the background.

In general, when you have a nanoparticle that is not well defined, what are the proper steps that I should start with? I looked into Noise for outlier removals, but should this be done before or after subtraction?

Here is an image. The scale bar is 20 nm, and the particles should be in the range of 2 -3 nm
NP-MSM.tif (4.0 MB)