With Super 8 and other motion picture stock, a sampling was always viewed for quality control. With still film, it varies with the lab. Quality control is essential, and a sampling is needed in all cases. Some smaller labs mount slides by hand and view each frame. For other work, a small lab will view each roll and may view each frame. Fully automated color negative labs vary a lot, but prints will be seen when packaging them into the customer return envelopes. Larger automated labs will view a sampling, possibly a large sampling, for quality control and will give a cursory look at each roll just to be sure the machines worked right.