Removing the hand from the equation

A tripod and a self-timer are the cheapest way to make a rating photo repeatable: the mount fixes distance and angle, and the timer removes the jolt of pressing the shutter. A hand-held photo carries a hand's worth of variation the photographer cannot see, and a rubric reading proportion from the frame can.

One fix, three variables

A tripod, or any fixed mount, removes distance drift and angle drift at once, because the camera is locked in place rather than eyeballed into position each session. Distance alone is not a small effect: modelling faces, Ward and colleagues (2018, JAMA Facial Plastic Surgery) calculated that a photo taken from 12 inches makes the nose appear 30% larger in men and 29% larger in women than an undistorted projection, with essentially no difference at 5 feet. A self-timer or remote shutter removes the small jolt of pressing the button by hand, which is its own source of last-second shift and blur. Blur matters to the model as well as the eye: Dodge and Karam (2016) tested four image classifiers and found them "susceptible to these quality distortions, particularly to blur and noise". Together they replace three separate sources of variation with one repeatable setup, which is the same standardisation goal covered in making a submission comparable - this is just the cheapest way to get there.

It is worth being precise about what this upgrades. Not image quality, not lighting, not composition - repeatability, specifically. A tripod does not make a photo look better; it makes the same photo reproducible, which is a different and, for this purpose, more valuable property, echoing the same point made about gear more broadly: expensive kit buys consistency, and a $15 tripod buys most of the same consistency for a fraction of the cost.

Marking the position

A mount only helps if it is set up the same way each time. Tape marks on the floor for the tripod legs, a note of the height, and the same distance from the subject turn "roughly the same spot" into an actual fixed reference. That written note is the part people skip, and it is the part that makes the setup a protocol rather than a habit.

This is a lighter version of what dedicated measurement gear achieves for a physical reading, and a much lighter version of what a professional photography session would set up to control the same variables - most of the benefit for almost none of the cost. It has no equivalent on the side of a human reviewer, since nothing about camera stability changes what a person receives to look at; it is a fix for the model side of the process specifically.

Ten minutes and a cheap stand solve a variable that no amount of careful hand-holding fully solves, and it makes any photo guide a tool publishes easier to actually follow twice.