Experimentation with calculations, long-distance travels abroad and close contact with friends around the world to collect empyrical data from professional non-doctored pictures (Yes, I run tests on them and collected both digital and analogical (polaroid) evidence to make sure nothing was altered and manipulated). I seldom trust anything just because it has been told me. I weight the evidence, check the data, apply my method, compare and contrast my thesis against opinions from others. If it's proven to be true not only in theory, but empirically after experimentation under the same circumstances, then I assume it to be true.
Experimentation with calculations, long-distance travels abroad and close contact with friends around the world to collect empyrical data from professional non-doctored pictures (Yes, I run tests on them and collected both digital and analogical (polaroid) evidence to make sure nothing was altered and manipulated).