Brightness and contrast correction for video extensometer systems and methods

A method for correcting brightness, contrast, or focus distortion of a test specimen, the method comprising:

• arranging a test specimen between an illuminated screen and an imaging device;
• imaging, via the imaging device, a silhouette of the test specimen against the illuminated screen;
• calculating, via the processing system, one or more characteristic measurements based on the imaging;
• accessing, via a processing system, a list of correction terms, wherein the correction terms are a function of one or more characteristics including brightness, contrast and focus;
• and
• determining, via the processing system, a correction term from the list of correction terms based on one of a brightness, a predetermined focus, or calculated focus of the imaging device;

A system for correcting brightness distortion of a test specimen comprising a processing system configured to:

• receive images from an imaging device of a test specimen during a testing process, wherein the imaging device is arranged opposite a reflective screen relative to the test specimen;
• measure one or more characteristics at one or more positions along an edge of the test specimen during the testing process;
• determine distortions along the edge of the test specimen in the images associated with brightness, contrast, or focus;
• and
• determine a corrective term based on the distortions.