Promoting Nancy’s photography and educating the public about nature, photography, and God

How To Find The Area Of An Object Using Photoshop

Mathematical or drafting programs may do a better job of finding the area of all sorts of seemingly random two-dimensional shapes.  And I may have used one or two of these as a student.  But I haven’t had any of them on my computer for many moons.  So when I recently needed to compare the size of the visible sun at different times during a solar eclipse to compare exposure levels, I was out of luck.  But then there was Photoshop.  I just finished an article about how to find an object’s area in Photoshop.  I put it on our website at, mainly because I mentioned the technique in an earlier blog post and was about to mention it again in an article I promised about the challenges of our newest eclipse image.  This probably isn’t the most common task you will be performing, but when you need it, this can be handy.  Enjoy!



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2 responses to “How To Find The Area Of An Object Using Photoshop”

  1. […] each sun appropriately. To do that I used Photoshop again to find the relative area of each sun, and then use that area to determine how much darker its part of the sky should […]

  2. […] I have some ideas for shooting the eclipse by either phone or SLR camera.  For those who haven’t heard, the next eclipse will be Monday, August 21st. In Miami, the eclipse will start around 1:30 pm, which is right after local apparent noon (when the sun crosses due south of us around 1:24 pm and is 77° above the horizon). The eclipse will last about three hours, by which time it will have reached an azimuth (compass bearing) of 261° and dropped to a height of 44°. At its peak just before 3 o’clock, it will be 64° above the horizon at a bearing of 243° (west-southwest). At that time, less than 1/5 of its diameter will be visible in South Florida, which means that about 22% of the sun’s area will still be showing, and the sun will still be a little less than 1/4 of its normal brightness (for lack of anything better at hand, I used Photoshop’s Count Tool to figure the sun’s brightness). […]

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