How to find the scale of the image

Hi there. I am brand new in ImageJ and generally image analysis programs. I am using this program to measure grain boundaries in crystals and get some charts. So I started doing the measurements in a lot of scanned thin sections and then I realized that I haven’t set any scale…

So now I have all my measurements in excel files but I can’t figure out what scale they have… is in in inches? in pixels? no idea.

When I open again the images, if I try to go to “Set Scale” in "analysis " drop-down menu, I get a number in pixels (but it is a different one for every image, although all the thin sections have approximately the same size).

Is there a way to find out the scale and do mathematically the changes from the current scale to the right scale? Or do i have to redo all my measurements???

Thank you in advance ! I hope I explained my problem correctly…

1 Like

@Maria_Eleni_Taxopoul

Just a couple of general ‘best practices’ here…

  1. Use Bio-Formats to open your images… File > Import > Bio-Formats This will ensure that your metadata (as long as it is present and correct) will get read in correctly when opening the image. The Drag&Drop method isn’t so reliable when it comes to metadata. So use Bio-Formats - for sure - try this first.

  2. You can always double-check your image scale by opening Image Properties. And yes - you are correct that you can adjust things as you need using Set Scale.

If none of that is fruitful… would you be able to share an original image file here with us so we can take a look ourselves? That would be best if things still aren’t working for you.

1 Like

Okay I see your point, I thought that the measurements were in pixels but it turns out that they are in inches, because I used the app Paint to draw some lines on the photo for the measurements. So the image now has 11.697.31 inches (58553664) and I guess the results are in pixels. I will upload the photos for you to check.

image

image

PS> I couldn’t upload the picture because it is very big. I send you screenshots with the inches and the auto-set scale. If you check the numbers on the last screenshot of my excel file (they are 2D measurements of grain boundaries) do you think that if I divide them with 500.99 I will get the pixels? I need to get the scale in mm.

1 Like

@Maria_Eleni_Taxopoul

You should be able to Set Scale and adjust to mm - no? As there are 25.4mm/inch - if you know how many pixels/inch (500.99pixel/inch) - you can calculate pixels/mm … should be 19.724pixels/mm - right? Then all your measurements will be in mm…

Yes I think you are right! I will try to do that. Thank you!

1 Like