Exam angle. Aperture, shutter and ISO all change how much light reaches the sensor. Three hooks: slower shutter, more light. Higher ISO, brighter but noisier. Small f-number, big hole, more light. The numbers feel backwards, so learn them now.

Exam angle. The aperture is the hole. f/2 is wide open, f/22 is a pinhole. For weld detail use f/16 or f/22 because a small hole gives deep focus. Underwater you pay for that with light, which is why you carry a strobe.

Exam angle. Why f/8 is a smaller hole than f/4. The f-number is focal length divided by hole diameter, so the number goes up as the hole shrinks. Once that clicks the exam question on aperture stops being a memory test.

Exam angle. Long focal length means narrow view and more magnification. Underwater, avoid heavy zoom. It cuts depth of field and magnifies hand shake. Move closer instead. Less water between lens and subject also means less colour loss and less backscatter.

Exam angle. Depth of field is the slice that is in focus. Small aperture, deep slice. Wide aperture, thin slice. A weld shot needs the toe and the cap both sharp, so stop down. Hold the camera at ninety degrees to the weld face so the toe profile is true.

Exam angle. Overlapping close-ups stitched into one full-length record. Overlap each frame by thirty to fifty percent. Put an ident marker parallel to the weld and a scale in every frame. Shoot a slate first with weld ID, date and your initials. Without the scale, size cannot be judged from the picture.