Troubleshooting Mobile App Camera Issues

Most mobile scanning problems come down to one of a few factors — lighting, camera angle, focus, or connectivity. This article walks through the common camera issues and how to fix them fast.

Quick Diagnostic Checklist

Before diving into specific fixes, run through this list. If you can answer yes to everything, you’re likely looking at an environment-specific issue covered further down.

Is there enough light to comfortably read the sheet with your eyes?
Is your phone held parallel to the sheet (not tilted)?
Are all four corners of the sheet visible inside the camera frame?
Is the camera lens clean?
Is the PaperScorer mobile app updated to the latest version?
Does your phone have an internet connection?

Issue 1: The Camera Won’t Auto-Capture

What it looks like: you position a sheet in frame, but the guide overlay never turns green and the app doesn’t capture.

Cause: Poor lighting - The app needs enough light to detect the QR code and corner alignment markers. In dim rooms, detection fails.

Fix: move to a brighter area or turn on a desk lamp. Overhead fluorescent or daylight LED lighting works well.

Cause: Camera held at an angle - The app refuses to capture when it detects the phone is tilted — an off-angle scan would distort the bubbles.

Fix: hold the phone directly overhead, parallel to the surface. All four corners of the sheet should be visible and roughly equidistant from the frame edges.

Cause: Too far or too close - The app has an optimal distance range. Too close and the corners are cut off; too far and the QR code is too small to read.

Fix: hold the phone about 12–18 inches above the sheet. Use the guide overlay as your target — when the sheet roughly fills the frame with a small margin, you’re in the right zone.

Cause: QR code obscured - If the QR code in the sheet’s corner is folded, stained, or covered (e.g. by a paper clip or sticker), the app can’t identify the sheet.

Fix: flatten the sheet and remove anything covering the QR code.

Issue 2: Scans Are Blurry

Cause: Shaky hands - At 12–18 inches, even small hand movements show up as blur.

Fix: stabilize the phone. Rest your elbows on a table while you scan, or use a small phone tripod if you scan in bulk regularly.

Cause: Dirty camera lens - Phone cameras pick up fingerprints fast, especially right next to the screen.

Fix: wipe the lens with a soft cloth or the corner of your shirt. This is almost always the culprit.

Cause: Low light - In low light, the camera lengthens exposure time, which exaggerates any motion blur.

Fix: add light, or as a last resort enable the flash. Flash can wash out bubbles, so try lighting first.

Cause: Autofocus locked on the wrong thing - Phones can mistakenly focus on the background instead of the sheet.

Fix: tap the sheet in the viewfinder to force focus on it.

Issue 3: Sheets Scan But Results Are Wrong

What it looks like: the scan completes, but the wrong student is identified, or bubbles are misread.

Cause: Student ID bubbles not filled clearly - The app captures the image; the engine decides which student it belongs to using the bubbled student ID. Smudges, partial fills, or stray marks confuse the read.

Fix: coach students to fill bubbles solidly and erase mistakes completely. See Understanding Scan Failures and How to Fix Them.

Cause: Glare washing out bubbles - Overhead lighting sometimes reflects directly off the glossy paper into the camera, creating a bright wash that hides bubble fills.

Fix: shift the sheet’s position relative to the light source — don’t tilt the camera. A small repositioning of the sheet usually eliminates glare.

Cause: Shadow across the sheet - Your own shadow (or someone else’s) covers part of the sheet.

Fix: stand to the side of the sheet, not directly over it. Your phone is overhead, but your body shouldn’t be.

Issue 4: The App Crashes or Freezes

Work through these in order:

Close and reopen the app. Most transient issues clear after a restart.
Restart your phone. Resolves OS-level glitches that affect the camera.
Update the app. Check the App Store (iOS) or Play Store (Android) for an available update.
Free up storage. If your phone is out of space, the camera capture buffer can fail. Aim for at least a few hundred MB of free space.
Reinstall. Last resort — uninstall, reinstall, and sign back in.

If crashes persist, contact support@paperscorer.com with:

Phone model and OS version (e.g. iPhone 14, iOS 18.1).
The app version number (shown in the app’s menu / About screen).
A description of what you were doing when the crash happened.

Issue 5: Scans Aren’t Uploading

Cause: No internet connection - The mobile app needs an internet connection to upload scans.

Fix: check your Wi-Fi or cellular signal, reconnect to a network, and re-open the app. Scans captured while offline are typically queued locally and uploaded automatically once you’re back online.

Fix: sign out and sign back in. Try signing into the web app at app.paperscorer.com first to confirm your credentials are correct.

Cause: Account or plan limit - If you’re on a free account that’s hit its trial limit, new scans will be rejected.

Fix: sign into the web app and check your account status. Upgrade to Teacher Pro to continue scanning.

“My password isn’t working”

Try signing in to the web app with the same credentials first. If that works, try the mobile app again — sometimes a typed password gets autocorrected on mobile.
Use Forgot Password on the login screen to reset.
Confirm you’re using the same email address you created your PaperScorer account with (not a different work or personal address).

“The app says my account is locked”

Repeated failed logins can lock an account briefly. Wait a few minutes and try again. If it’s still locked, contact support@paperscorer.com.

Getting Better Results Over Time

After your first scanning session, review the results in the web app. You’ll quickly see which environmental factors (lighting position, distance, angle) produce the cleanest scans for your specific room. Once you’ve dialed in your setup, the mobile app is one of the fastest ways to grade a stack of sheets.