Face Size & PD Measurement
Face Size & Try Frames
Position your face in the camera — we'll measure your face and help you find the best fitting frames.
Do you have a prescription?
Upload it now and we'll extract your Pupillary Distance (PD) automatically — so face size estimation will be more accurate.
JPG, PNG or PDF — photo of your prescription slip
Don't have a prescription or don't know your PD? We'll estimate it automatically from your iris size during the face scan.
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Frequently Asked Questions for Human Face Ai
How accurate are the Nations Optics AI face measurements?
Nations Optics Smart AI captures measurements from 3 averaged frames — delivering clinically useful accuracy for eyeframe sizing and PD estimation.
Measurement accuracy at a glance
Measured cheek-to-cheek for a precise horizontal fit. Typical accuracy ±2–3 mm.
~1.5–2% errorPrecisely estimated from your eye positions. With your prescription PD entered, accuracy improves to ±0.5–1 mm.
±0.5–1.5 mmMeasured across the bridge of your nose. Consistent across scans; ±1–2 mm variation depending on lighting and head tilt.
±1–2 mmCalculated from your temple-to-temple span for a flush, balanced fit. ±2–3 mm expected range.
±2–3 mmWhy 3 captures?
Every scan averages 3 auto-captured frames taken in quick succession. This smooths out micro head-movements and ensures a stable, reproducible reading every time.
My PD reading varies slightly between scans — is that normal?
Yes, a variation of 0.5–1.5 mm between scans is completely normal — and here is exactly why it happens and how to work with it.
Why PD varies between readings
- Eye position sensitivity — even tiny shifts in your eye position during scanning can result in a small variation in the reading.
- Head distance drift — moving slightly closer or further from the camera changes the scan scale, shifting all distance readings slightly.
- Lighting asymmetry — uneven light causes one iris to appear slightly larger, shifting the detected centre by a sub-pixel amount.
- Lighting conditions — shadows or uneven light can affect how your eyes are detected in the scan, causing slight shifts.
How to get your most accurate PD
- Take 3–4 separate scans in the same session — the system auto-averages 3 frames per scan.
- Compare the PD values across scans — the most-repeated value is your most accurate reading.
- If you have a prescription from your optician, enter that PD using the Override PD option — it helps calibrate all your measurements for even better accuracy.
- Scan in consistent, even front lighting — avoid strong side light or backlighting.
For prescription lens cutting — always use the PD measured by your optician. Nations Optics AI PD is excellent for frame fitting and size recommendations, but optical-grade precision (±0.25 mm) requires professional equipment.
Why does Nations Optics AI take 3 automatic captures instead of just one?
A single frame is not enough for reliable measurements. Our scan pipeline uses a 3-stage averaging system to give you the most stable, reproducible result possible from a standard webcam.
How the 3-capture pipeline works
1
Stability check — before any capture, Nations Optics AI checks that your face is correctly positioned, centred, and steady. This ensures your head is truly still — not just for a single moment.
2
3 captures in quick succession — once your position is confirmed stable, Nations Optics AI takes 3 captures a moment apart. Each capture is sent to our Nations Optics AI server for full face analysis and real-world measurement.
3
Averaged result — all measurement values (face width, PD, nose bridge, etc.) from the 3 captures are averaged together. Outlier frames (e.g. from a tiny blink) are naturally diluted. The final result is statistically more stable than any single capture.
The result: smaller error, better fit
In testing, 3-capture averaging improved measurement precision by over 60% compared to a single capture — giving you a more reliable fit recommendation without any extra hardware.
What exactly does Nations Optics AI measure — and what do those numbers mean?
Nations Optics Smart AI captures 7 distinct measurements from your face — each mapped to a real-world use in eyeframe fitting.
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Face Width
Cheek-to-cheek horizontal distance. Used to determine frame size category (S / M / L) and whether a frame will sit flush.
Typical: 125–155 mm↕
Face Height
Forehead top to chin bottom. Helps distinguish Oblong from Square or Oval face shapes and informs lens height suitability.
Typical: 175–225 mm↔
Pupillary Distance (PD)
Centre-to-centre distance between your pupils. Critical for centring prescription lenses in any frame. Most important for lens cutting.
Typical: 56–68 mm●—●
Inner Eye Distance
The gap between the inner corners of both eyes. Closely matches the bridge width you need in a frame — prevents pinching or gaps.
Typical: 25–38 mm
Nose Bridge Width
Measured across the nose at the inner-eye level. Helps match frames with narrow or wide nose bridges to ensure the frame sits evenly.
Typical: 13–22 mm☀
Ideal Eyeframe Width
Calculated from your overall face span. This is the total front width of an eyeframe that will sit flush without extending past your face.
Typical: 125–148 mmFace Shape (7th output)
Nations Optics AI analyses your face proportions and classifies your face as Oval, Round, Square, Heart, Oblong, or Diamond — and maps it to the best-fitting frame styles in our catalogue.
How do I get the most accurate scan result?
Accuracy is directly tied to how well you set up the scan. Follow these steps to get measurement-grade results from a standard webcam.
Before you start
- Remove all eyewear — glasses, sunglasses, reading glasses, and goggles. Contact lenses are fine.
- Remove face coverings — masks or anything that covers your lower face will affect scan accuracy.
- Choose even front lighting — sit facing a window or bright light, not with it behind you. Avoid strong side shadows.
- Use a laptop or desktop for the first scan — fixed cameras give more stable frames than handheld mobile.
During the scan
- Keep your head at arm's length (approx. 45–55 cm) from the camera. Too close or too far affects scan accuracy.
- Align your nose tip to the yellow dot exactly — this ensures your face is centred and distance is consistent.
- Look straight into the lens — even a small head turn shifts the face-width reading by 3–5 mm.
- Hold still for 1.6 seconds until the oval turns green — the system auto-captures once your pose is stable.
- Do not rush — if the oval stays amber, adjust your position. Forcing a capture while unstable reduces accuracy.
For the highest PD accuracy
Enter your PD from your optician's prescription using the Override PD field before scanning. This value is used as the real-world calibration anchor — it improves not just PD, but all distance measurements improving the accuracy of all your measurements.
Pro tip: Take 2–3 separate scans and compare readings. The measurement that repeats most consistently across scans is your true face size. Our system automatically uses the most recent completed scan for Virtual Try-On.
What does my face shape result mean — and which frames suit me?
Face shape is calculated from the proportions of your face width, height, forehead, and jaw — analysed by Nations Optics AI. Here is what each shape means and which frame styles complement it best.
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Oval
Balanced proportions — slightly wider forehead, gentle chin. The most versatile face shape. Almost all frame styles work well.
Any frame style
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Round
Width and height are nearly equal with soft curves. Angular or rectangular frames add definition and make the face appear longer.
Rectangle / Geometric
⬛
Square
Strong jaw and forehead of similar width. Round or oval frames soften the angles. Avoid boxy frames that echo the face shape.
Round / Oval
♥
Heart
Wider forehead tapering to a narrow chin. Bottom-heavy or rimless frames balance the forehead. Avoid top-heavy browline frames.
Light / Rimless
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Oblong
Longer than wide with a straight cheekline. Taller frames (large lens height) or wide frames add width and balance the length.
Wide / Deep frames
♦
Diamond
Narrow forehead and jaw with prominent cheekbones. Cat-eye or oval frames with detailing at the top complement the cheekbone width.
Cat-eye / OvalFace shape is a guide, not a rule. Use the Virtual Try-On after your scan to see actual frames at the correct scale on your real face photo — which is far more reliable than shape alone.
How does the Virtual Try-On work after my scan?
Virtual Try-On overlays actual frame product images on your scanned face photo at the correct real-world size — using your scan data as the reference.
Step-by-step: how the overlay is positioned
1
Your eyes as anchor — Nations Optics AI uses the position of your eyes as the reference point to place the frame exactly where it would naturally sit on your face.
2
True-to-size scaling — the frame's real-world dimensions from the product listing are matched to your scan measurements, so the frame appears exactly as large as it would actually sit on your face.
3
Clean frame overlay — Nations Optics AI cleanly places the frame on your photo, keeping frame colours true to life — no special setup needed.
4
Opacity slider — adjust from 30–100% to see how opaque or see-through the frame appears. Lower opacity helps verify bridge and temple alignment on your face.
Best results: use frames that have product images specifically from a front-facing angle. The View Product button on each try-on frame takes you directly to that frame's listing — where you can check exact mm dimensions before ordering.
Is my face data private? What happens to my camera feed?
Your privacy is taken seriously at every step. Here is exactly what happens to your camera feed, your scan images, and your measurements.
Camera feed — stays in your browser
The live camera stream is processed entirely inside your browser using Nations Optics AI face detection — built into your browser. The raw video feed is never transmitted to any server. Only the captured still-frame images are sent for analysis on our secure Nations Optics server.
Captured images — processed and stored privately
The 3 captured frames are sent to our Nations Optics server (not any third-party AI cloud). An annotated version with measurement lines is generated and stored in your account so you can review your last scan. Images are stored in a private server directory — not publicly accessible via URL without authentication.
Measurements — saved only to your Nations Optics account
Face width, PD, nose bridge, and all other measurements are stored in your Nations Optics profile. This data is used exclusively to power the Virtual Try-On and frame size recommendations on product pages. It is never sold or shared with any third party.
Camera: browser-only processing
Images: private, authenticated access only
Measurements: your account only
No third-party data sharing
Want to delete your scan? Click Scan Again on the face scan page. This deactivates your current face profile and removes all associated measurement data from our system. You can re-scan at any time.
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👋 Hi! I'm your Nations Optics assistant. Ask me anything about lenses, frames, or prescriptions!