Data analysis of images

I have microscope images of spherical particles. What I need is diameter information and center to center distance of the nearest neighbor for all the particles. I am using ImageJ (which is a free image processing software). I create a black and white image and split clustered particles with Paint. I enter the scale information and calculate the area with ImageJ. In Excel I convert the area data to diameter and create a histogram. For nearest neighbor distance, I find maxima of the images (with ImageJ, after entering the scale) which corresponds the center of the particles. (For clustered particles I mark the center with white before.) I transfer the coordinate data to Excel. I have a Macro which calculates the nearest neighbor distance for each particle. Then I create the histogram. I have 44 images for distance, 45 for size calculation. I will provide tools, however you are free to develop and use yours. Precision is very important. If you are familiar with image processing it is not a hard project. I have 6 sets of images. What I need is: For size: 1 - Size distribution data for each image, 2 - Black an white mask image, 3 - Size distribution data of each set (combined data). For distance: 1 - Distance distribution data for each image, 2 - Distance distribution data for each set. You can see the samples here: [login to view URL] [login to view URL]