> ## Documentation Index
> Fetch the complete documentation index at: https://docs.symetri.app/llms.txt
> Use this file to discover all available pages before exploring further.

# Photography Guide

> How to photograph patients so Symetri's AI alignment is fast, accurate, and consistent every time.

## Introduction

The quality of your Symetri results depends directly on the quality of your photos. Symetri uses AI-powered face alignment — detecting up to 10 landmark regions including eyes, nose, mouth, brows, and face contour — to automatically align your before and after images for a precise, professional comparison.

***

## The Four Golden Rules

These apply to every shot you take:

<CardGroup cols={2}>
  <Card title="Same angle every time" icon="rotate">
    Before and after must match in yaw (left/right rotation), pitch (up/down tilt), and roll (head tilt).
  </Card>

  <Card title="Same distance every time" icon="arrows-left-right">
    Keep the camera the same distance from the patient's face across sessions.
  </Card>

  <Card title="Camera at eye level" icon="eye">
    The lens should be level with the patient's eyes — not above, not below.
  </Card>

  <Card title="Consistent, diffuse lighting" icon="sun">
    Avoid hard shadows across the face. They obscure the landmarks the AI uses for alignment.
  </Card>
</CardGroup>

***

## How Symetri Sees Faces

Symetri's AI scores each photo's landmark quality on a 4-point scale before deciding how to align your pair:

| Score     | What it means                                      | Alignment quality                     |
| --------- | -------------------------------------------------- | ------------------------------------- |
| **4 / 4** | Both eyes clearly visible, nose and mouth detected | Highest precision — 4-point alignment |
| **3 / 4** | One eye clearly visible, nose and mouth detected   | Good — 3-point alignment              |
| **2 / 4** | Nose and mouth only (face turned away)             | Basic — 2-point alignment             |
| **\< 2**  | Landmarks not detected                             | Fallback to face bounding box         |

<Tip>Keep both eyes in frame and unobstructed whenever the treatment allows. That's the difference between a score of 4 and a score of 2.</Tip>

### The 28° Rule

When the face is rotated more than **\~28° away from camera**, the AI switches from its highest-quality 4-point alignment to a simpler 2-point mode using only the nose and mouth — because at that angle, the far eye becomes unreliable. This is by design.

**What this means:** If you're shooting a 3/4 view, both photos need to be at *exactly* the same degree of turn. A 28° before and a 35° after will produce a visible alignment mismatch.

***

## General Setup

### Equipment

* **iPhone (rear camera, 1× lens)** — the primary lens. Avoid ultrawide (0.5×) which distorts facial proportions.
* **Tripod or stabilized arm** — eliminates distance variation between sessions.
* **Ring light or softbox** — even, diffuse illumination positioned directly in front of the patient, level with the face.
* **Neutral background** — white, light gray, or medium gray.

<Tip>Mark the floor with tape for where the patient stands and where the tripod sits. This ensures every session starts from the same spot.</Tip>

### Ideal Framing by Treatment Profile

| Profile          | Top of frame          | Bottom of frame | Width                                   |
| ---------------- | --------------------- | --------------- | --------------------------------------- |
| **Full Face**    | 1–2 cm above hairline | Chin + 3 cm     | Shoulders barely visible                |
| **Forehead**     | 2–3 cm above hairline | Tip of nose     | Face edge to edge                       |
| **Eyes**         | Top of brows + 2 cm   | Mid-nose        | Ear to ear                              |
| **Lips**         | Nose base + 1 cm      | Chin + 2 cm     | Corner to corner + 3 cm                 |
| **Side Profile** | 1–2 cm above hairline | Chin + 3 cm     | Full profile — forehead to back of head |

<Warning>
  **Common framing mistakes:**

  * **Too close:** Forehead or chin cut off. The face detector uses the full face contour — clipping it degrades alignment.
  * **Too far:** Face occupies less than \~30% of the frame. Detection still works but precision drops.
  * **Camera tilted:** Even a small roll causes a corrective rotation that may not match perfectly — keep the grid lines level.
</Warning>

***

## Frontal Photos

Frontal is the highest-quality mode for Symetri. Both eyes are detected, giving full 4-point landmark alignment.

### Patient Positioning

* Patient faces directly into the camera. Both eyes equally visible and equidistant from frame edges.
* The nose tip should point straight at the lens — no chin lift, no chin drop.
* Hair pulled back off the face. Stray hair over one eye forces the AI into 3-point (one-eye) mode.
* Eyebrows relaxed. Squinting reduces landmark confidence.

### Chin Angle

Use the **Frankfort horizontal plane** as the gold standard: the line from the tragus of the ear to the infraorbital rim should be level with the floor. In practice: the patient looks straight ahead, eyes level with the horizon — not at the camera screen.

### Lighting

* Ring light centered directly behind the camera, level with the patient's eyes.
* **No** overhead downlighting — it casts heavy shadows under the eyes and nose.
* **No** sidelighting — it creates asymmetric shadows that can confuse eye detection.

### Frontal Checklist

<Steps>
  <Step title="Both eyes fully open and visible" />

  <Step title="No hair across either eye or brow" />

  <Step title="Nose tip pointing directly at lens" />

  <Step title="Face centered horizontally in frame" />

  <Step title="Camera level with patient's eyes" />

  <Step title="Hairline to chin fully in frame" />
</Steps>

***

## Side Profile Photos

Side profiles are the most demanding for Symetri's AI. At 90°, only the nose and mouth are used as anchors — rotation correction is disabled. Your camera angle must be **identical** between before and after.

### 90° vs. 45° Tradeoff

| Angle               | Alignment quality                 | Consistency requirement              |
| ------------------- | --------------------------------- | ------------------------------------ |
| 45° (three-quarter) | Higher — both eyes may be visible | Must replicate angle precisely (±5°) |
| 90° (true profile)  | Lower — nose + mouth only         | Must replicate angle precisely (±2°) |

**Recommendation:** Pick one standard and stick to it. A 45° view gives Symetri more to work with.

### Profile Checklist

<Steps>
  <Step title="Consistent angle — mark the floor with tape to standardize turn" />

  <Step title="Ear on camera side fully visible" />

  <Step title="No hair across nose or mouth" />

  <Step title="Chin level — not lifted or dropped" />

  <Step title="Camera at eye level, not above or below" />
</Steps>

***

## Eyes Profile Photos

The Eyes profile zooms into the periorbital region using a 1.2× focus with the eyes as the anchor point.

<Warning>Shoot the full face as normal — Symetri's Eyes profile handles the zoom digitally. Do not zoom in with the iPhone camera. This preserves all pixel data for alignment before the crop is applied.</Warning>

* Eyes **open naturally** — not wide-open, not squinting.
* A ring light centered on the lens will produce a consistent circular catchlight. Avoid double catchlights from two light sources — they can confuse the eye landmark detector.
* Avoid strong overhead light that creates a heavy shadow under the brow bone.

***

## Lips Profile Photos

The Lips profile zooms into the mouth region using the mouth centroid as the anchor point.

* Lips **at rest** — slightly parted (2–4 mm) is acceptable.
* Use the **same expression for both sessions**. A pout vs. rest position will throw off alignment.

<Tip>Wait at least 2 weeks post-filler before shooting the after photo. Swelling in the first 1–2 weeks alters the lip border shape and will affect the AI's mouth contour detection.</Tip>

***

## Forehead Profile Photos

The Forehead profile zooms into the upper third of the face.

* Hair pulled **completely off the forehead** — hairline must be fully visible in both shots.
* Patient looks straight ahead. Avoid chin lift (shortens visible forehead) or chin drop.
* Eyebrows **relaxed** — not raised or furrowed. Don't ask the patient to raise their brows for the photo.

***

## Lighting Reference

| Lighting setup                  | Quality   | Notes                                 |
| ------------------------------- | --------- | ------------------------------------- |
| Ring light, centered, eye level | Excellent | Consistent catchlights, even coverage |
| Bilateral softboxes, 45°        | Excellent | Even, shadow-free                     |
| Single softbox, 45°             | Good      | Slight shadow — keep consistent       |
| Window light (cloudy day)       | Good      | Diffuse and even                      |
| Window light (sunny day)        | Fair      | Changes throughout day                |
| Overhead downlighting           | Poor      | Heavy under-eye and nose shadows      |
| No controlled lighting          | Avoid     | Varies session to session             |

***

## Common Problems and Fixes

| Problem in Symetri                 | Likely photography cause                  | Fix                                             |
| ---------------------------------- | ----------------------------------------- | ----------------------------------------------- |
| After image shifts on case open    | Camera angle or chin position changed     | Re-shoot; use Manual Alignment as temporary fix |
| Face appears off-center or clipped | Patient too close or framing too tight    | Move patient back; ensure full face in frame    |
| Images don't align on one side     | One photo is slight 3/4 vs. the other     | Standardize angle; use a wall reference mark    |
| Eyes not detected / blur misplaced | Hair over eyes, squinting, or shadows     | Pull hair back; adjust lighting                 |
| Lips profile shows misalignment    | Different lip expression between sessions | Same expression — lips lightly closed or parted |

***

## Quick Reference Card

```
SYMETRI PHOTO PROTOCOL

SETUP
  ✓  Tripod on taped floor marks
  ✓  Camera at patient's eye level
  ✓  Ring light centered, eye level
  ✓  Neutral background

EVERY SHOT
  ✓  iPhone rear camera, 1× lens
  ✓  Lock exposure on patient's face
  ✓  Grid lines level
  ✓  Full face in frame (hairline to chin)
  ✓  Same angle as before session

FRONTAL  →  Both eyes visible, nose to camera
PROFILE  →  Mark floor angle, ear to camera
EYES     →  Full face frame, eyes open naturally
LIPS     →  Lips at rest, same expression both times
FOREHEAD →  Hair off forehead, brows relaxed

NEVER
  ✗  Zoom past 1×
  ✗  Shoot in different lighting than before
  ✗  Let patient change chin angle mid-session
  ✗  Crop in-camera before shooting
```