How to measure percentage of empty space in an image?

[thereser67177405]

I am running an experiment to see how long it takes cells growing in culture to fill in an empty area. I am trying to measure how much empty space is between the cells in my cell culture dish. I need to know how I can use Photoshop to see what percentage of the field is covered and what percentage is empty.

[Norman Sanders · Accepted solution]

If you can make a selection of the cells Photoshop will provide the figures that will allow you to make the calculation, Choose the Histogram panel and on the upper right corner, choose Expanded View. Pixels will tell you the pixel count of total area. Make a selection of the cells and the Pixel figure will change to reflect the number of pixels within the selection(s). From those two numbers you may do the math.

[thereser67177405]

Thanks so much! The only change I had to make was to access the Histogram window, I had to click on Window at the top of the screen and select Histogram from the drop-down menu.

[davescm]

When you make a selection the number of pixels selected is shown in the histogram panel. So you could make a selection of the petri dish to get the total and then make a selection of the growth (or space ) using select color or similar. Then it is simple division.

Dave

Edit : Norman got there first whilst I was typing

[Norman Sanders]

The posting times may not reflect that, Dave, because went back and edited it a tad for greater clarity. More important, I hope it solves his problem.    

[thereser67177405]

Thanks so much!