This is a flock of birds in flight taken at the Sacramento National Wildlife Refuge.  Using ImageJ, I opened this image, set the image type to 8-bit, and adjusted the threshold to create a black and white image.  Then I analyzed the particles to find out how many birds are in the photograph.  This analysis generated an image where each bird was outlined and counted (the second image of black outlines of the birds).

The data showed that there were 38 birds in this photo.  The actual number is higher, about 45 birds in whole or partial.  The reason for the lower count generated by ImageJ is likely due to overlap of birds.  Therefore, two to three birds may be counted as one bird due to the flattening and blocked color of the analyzed image.

ImageJ is a fantastic tool and would be hugely helpful in counting many small objects in an image. For example, ImageJ will be useful in counting the number of visible colonies on a Petri dish, the number of cells in a slide, etc.

Another practical application of ImageJ is scaling.  One can set a scale in an image (the example we worked through in the workshop is of tree rings), and use ImageJ to measure the length of each tree ring once the scale is set.