Flash-Cue Timing
Capture Card & DSLR Latency Auditor
Measures the real glass-to-glass delay for any camera device you select — a DSLR through a capture card, a native USB webcam, or a virtual camera — by firing a bright flash on screen and timing exactly how long it takes to detect that flash in the device's own captured frames. Test each device you own and compare the numbers directly.
Status
Select a device and click Start, then point that camera back at this screen.
Result
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Average Glass-to-Glass Latency
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Run history: —
Notes
Where the delay actually comes from
Native USB webcamTypically the lowest latency path — sensor, USB transfer, browser decode, with few intermediate stages.
DSLR + HDMI capture cardAdds sensor processing on the camera itself, HDMI output, capture card encoding or pass-through, then USB transfer — each stage measurable, and this tool measures the sum of all of them.
Virtual cameras (OBS, ManyCam, etc.)Add a software compositing stage on top of whatever real device feeds them — test the virtual camera device directly to capture that additional delay.
Reference
Typical Latency by Device Type
| Device type | Typical range | Why |
|---|---|---|
| Native USB webcam | Roughly 50 – 150 ms | Fewest processing stages between sensor and browser. |
| DSLR + HDMI capture card | Roughly 100 – 300 ms | Camera processing, HDMI, capture card encode, USB transfer. |
| Virtual camera (OBS, etc.) | Adds on top of the source device | Extra software compositing stage before reaching the browser. |
General reference ranges, not a guarantee — actual results vary by specific hardware and drivers, which is exactly what this tool measures directly for your setup.
Step-by-Step
How to Run the Test
- Select the device you want to test from the dropdown.
- Click "Start" and allow camera access when prompted.
- Point that camera back at this screen so it can see the flash when it fires.
- Click "Measure Latency" and repeat 2-3 times, then compare across devices by switching the dropdown.
Common Issues
Troubleshooting & Fixes
"No flash detected"Make sure the camera being tested can clearly see this screen, with the flash area unobstructed and not too far away.
Camera access blockedClick the camera icon in your browser's address bar to confirm this site is allowed, or check your OS's camera privacy settings.
Results vary noticeably between runsSome variation is normal and expected — resolution is limited to roughly one camera frame interval. Look at the typical value across several runs rather than any single one.
Want to reduce latencyUpdate your capture card's drivers and firmware, avoid unnecessary USB hubs, and check for a "low latency" or "game mode" setting in the capture card's own software if available.
Common Questions
Frequently Asked Questions
What is glass-to-glass latency?
The total delay from light hitting the camera's lens (glass) to that image appearing on your screen (glass) — covering the sensor, any capture card encoding, USB transfer, and the browser's own decode and render pipeline all at once.
Why do capture cards add latency compared to native webcams?
A capture card has to receive an HDMI signal, encode or pass it through, and hand it to the OS as a virtual camera device — each stage adds a small delay a native USB webcam's more direct pipeline does not have. This measures the real total rather than assuming a figure.
How accurate is this measurement?
Resolution is limited to roughly one camera frame interval, the same practical limit as the site's A/V Sync Test. Run it several times and look at the pattern across runs rather than trusting any single reading.
Does this measure audio latency too?
No — this specifically measures video glass-to-glass latency using a visual flash cue. For combined audio/video sync measurement, the site's A/V Sync Test uses a clap test to measure the offset between the two.
Why does latency matter for streaming or calls?
High glass-to-glass latency delays your own reaction time relative to what you're seeing, and on a multi-camera switching setup, mismatched latency between sources causes visible desync when cutting between them.