New member here....needs help

living · June 12, 2005

Hi all,

I am new here, but have been viewing this forum for some time.But i will say was pushed into joining cos i have a problem and hope guys can help out. I have a pic on a particular steel, consisting of black and gray matters/grains. Now i dont know how i can measure its dimensions separately and its area in pixs or other units prefarably.Is it possible with Photoshop?

Shay Stephens · June 12, 2005

Can you rephrase this? I don't understand what the problem is or what you need.

If I had to guess, it sounds like you have a photo with a lot of noise (grain) and you want to know what the pixel dimensions of the image is (e.g. 1600x1200) and want to know if photoshop gives you this information.

If that is the problem/question, then yes, there is an answer. The easy way is to go to the menu and select Image, then select resize. In the resize box, it will tell you what the current dimension are in pixels. If it is not in pixels, then change the unit of measure with the small drop down box to the right.

If that was not your problem/question, then please rephrase it and be very specific. Don't use abbreviations, spell everything out for clarity.

living wrote:

Hi all,

I am new here, but have been viewing this forum for some time.But i will say was pushed into joining cos i have a problem and hope guys can help out. I have a pic on a particular steel, consisting of black and gray matters/grains. Now i dont know how i can measure its dimensions separately and its area in pixs or other units prefarably.Is it possible with Photoshop?

living · June 12, 2005

Ok, Shay i will be more elaborate.

Well i work on steel and from time to time i get its image/picture , now this steel pic/image consists of black and gray grains of irregular sizes, i will just like to measure its diameter and area in (microns prefarably) pixels.I dont know how it is done.I will try out what you wrote if it works i'll holla at you.

Shay Stephens · June 12, 2005

Oh! You want to directly measure the size of the grains as shown in the photo. Kind of like when NASA takes a photo on Mars of a crater, and by counting how many pixels there are from crater edge to crater edge they know that the crater is 2 kilometers in diameter.

Well in that case, what you need to do is know how far away the camera is from the surface being photographed. You have to calibrate the setup so you can reliably take similar pictures and know that one pixel = x microns.

If this has to be a portable setup, then having some kind of clear lens hood would allow you to place the camera directly against the surface being imaged. The surface to camera distance would always be the same.

With that in place, I would then place a measuring tool on the surface, photograph it, then in Photoshop count how many pixels are between 1 mm, or centimeter, or whatever your setup allows. Then you will be able to determine how much space one pixel occupies, and, then determine how big details are in the image by simply counting pixels.

It sounds like an interesting project. Keep us up to date please.

living wrote:

Ok, Shay i will be more elaborate.

Well i work on steel and from time to time i get its image/picture , now this steel pic/image consists of black and gray grains of irregular sizes, i will just like to measure its diameter and area in (microns prefarably) pixels.I dont know how it is done.I will try out what you wrote if it works i'll holla at you.

XO-Studios · June 14, 2005

living wrote:

Ok, Shay i will be more elaborate.

Well i work on steel and from time to time i get its image/picture , now this steel pic/image consists of black and gray grains of irregular sizes, i will just like to measure its diameter and area in (microns prefarably) pixels.I dont know how it is done.I will try out what you wrote if it works i'll holla at you.

I have actually done this application for a living.

You need an intermediate step, calibration
During calibration put an object of a known size in the center, and towards each of the edges of the field of view (looks like the image of a metalurgical microscope)

Using the measurement tool behind the eyedropper in PS, measure the distance of each object in pixels or whatever dimension. Now you use these three measurments to calculate a pixels/micron distance, and average it between center FOV and outside FOV.

Voila

XO,

ps. feel free to PM me, as I used to do applications like these for a living in industrial vision applications.

New member here....needs help

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