Dear Guillermo Uceda Gómez ,

In order to measure the real length of a feature in a picture you have to kniow scaling down factor of these pictures, the reduction factor. So during the imaging you can put in the filed of the view a linear light with a known length. Or you can use any other means to determine the scaling factor.

Best wishes

Dear Guillermo Uceda Gómez

Please send me a sample image to give you a precise answer.

Regards,

Gamal

If possible take the image of "millimeter grid" at the same distance as your target and compute the scaling factor as Zekry above suggest...

Abdelhalim abdelnaby Zekry and Sami Varjo the pictures are scaled with a milimetric grid. This grid is composed of squares of 1 cm, which are divided in 10 squares of 1 mm

Dear Guillermo Uceda Gómez ,

I know that you have a mesh on the picture but this is to measure the distance on the picture. You need to know how one centimeter on the pictures corresponds to what length in the real scene. This the scale factor. which is the ratio pf the length in the picture to the corresponding length in real scene. So in order to get out such scale you have to determine it experimentally as I indicated above or you must know the reduction ratio from the optic of the camera.

Best wishes