So I'm working on my master's thesis using Photoshop CC. I have 4 points punched into a scanned image. The distances between the 4 holes are know distances, figured to 1/10,000 of a mm. So, i'm not new to Photoshop and I know how to use it, but there's an error that I cannot get around.
When I use analysis and create a custom measurement scale using my known distance from the two vertical punches, my vertical is on, but my horizontal measurements (and subsequently, my overall line) are off and vice versa for scaling horizontally. Say my punches are 155.67mm apart and I scale vertically, the horizontal will read, say, 155.95. Not much difference you say? It's huge for my masters.
So, I figured that the reason it was off was due to the lines not being perfectly perpendicular to the x or y axis, so I straightened the image to that line. That way, 155.67 was going straight through the middle of the pixels on it's way down. No better outcome.
So, I figured that the size of the pixels is off, and tried to come up with an equation to account for some odd pixel size ratio, but that only got me a little closer and not really where I need to be.
I believe that this is a glitch in the coding but I cannot move forward with my project until I am sure about what's going on here. Anyone have any answers for me? I would REALLY appreciate it.