How to take progress photos that actually compare, on iPhone

• The spot: a fixed mark on the floor, in front of the same plain wall or door.
• Distance and height: the phone at the same height (chest height is common) and the same distance, so the subject fills the same part of the frame.
• Lens and zoom: the same lens, 1× for example. Switching lenses changes proportions, not just framing.
• Light: the same window, the same lamps, the same time of day. Overhead or side light changes shadows and can make the same body look different.
• Pose and clothes: the same stance, relaxed rather than flexed, in the same fitted clothes.
• Orientation: all portrait, or all landscape.

A selfie in a mirror changes the angle every time. Lean the phone on a shelf or a tripod at the same height and use the Camera's timer: open the Camera, tap the timer control and choose 3 or 10 seconds (the control sits in a menu in current iOS versions, so the exact place depends on your version), then press the shutter and step into position. The front camera is less sharp than the back one, so the back camera with a timer gives better detail.

Turn the grid on under Settings → Camera → Grid. The lines help you keep the horizon and doors straight and put your head and feet in the same cells every time.

Memory is a poor guide to a position from a month ago. Three habits help:

• Mark the spot with tape and mark where the phone stood or leaned.
• Open the last photo on a second device or print it, and match fixed features at the edges of the frame: a door frame, a socket, the line where wall meets floor.
• Take the shot, then flip between the new and the old one in Photos before you decide it is good. If something jumps, retake it now.

Every week or two is enough for most people; changes are slow, and daily photos mostly show noise. Pick one day and one time and keep it: the same morning, before eating and after the same routine.

Write down the date and any number you track next to the photo, such as weight or a measurement, or the plant's height. A photo alone says little; a photo with a date and a number tells a story. Do not rely on file names or hidden data for the date: a photo that goes through a chat app often loses them.

These are personal photos, so decide where they live before you take the first one.

• In Photos, open a photo, tap the more (…) button and choose Hide. Since iOS 16 the Hidden album is locked behind Face ID, Touch ID or your passcode by default, and it stays out of the main library view. The exact wording depends on your iOS version.
• If you use iCloud Photos, the hidden photos sync with the rest of your library; check that is what you want.
• Before sending a photo to a coach or a friend, look at its location: Share → Options → Location off. If you took the photos at home, that location is your address.

Photos show how something looks in one light on one day; they say nothing about health. Water, time of day, posture and a bad camera angle change how a body looks within hours, so a single "worse" photo means little. Look at the trend over several weeks, and talk to a doctor or a coach, not a photo, about anything that affects your health.