It is mainly used to quickly verify whether the camera permissions and preview are normal, and provides auxiliary indicators such as clarity (trend), average brightness, and dark/highlight cropping to help you determine whether the focus, exposure, and ambient light are appropriate.

Won't. Preview and analysis are completed in the local browser, and the page will not upload your camera video stream or screenshots.

You may have selected "Deny" in the browser permission pop-up, or the site permissions may have been set to block. Please change the camera permission settings in the address bar to "Allow" and refresh the page to try again.

iOS/Safari usually requires an HTTPS environment to call the camera (there may be exceptions for localhost). Please make sure to use https to access, or switch to a browser with better support (such as Chrome/Edge).

Resolution constraints are "ideal", and whether they ultimately take effect depends on the device/driver/browser. You can switch browsers, try different presets, or switch to the default resolution in the system/camera app and test again.

no. Clarity is a trend indicator based on picture sampling, and is more suitable for comparison on the same device/same scene (such as moving distance, switching lights, stabilizing the device before and after). It is not recommended to directly compare values ​​between different devices.

The indicator only covers some features (such as edge sharpness and brightness statistics) and cannot fully represent all subjective feelings. It is recommended to compare screenshots, observe details and sports scenes, and retest under different light/distance/stability conditions.

First check if there is an error message (such as permission denied/device does not exist/device is occupied). If there is no prompt but the screen is still black, you can try: refresh the page → switch to another camera → click "Apply and restart" → close the application that is using the camera (conferencing software/screen recording/camera) → change the browser (the compatibility of Chrome/Edge/Safari/Firefox varies greatly).

It may be that the device does not have a camera, the camera is disabled by the system, or the browser cannot enumerate the device. You can confirm that the camera is available in the system settings; if it is an external camera, re-plug the USB and click "Refresh"; you can also change a browser to verify whether it is a browser-side restriction.

This usually means that the camera is being used by other applications (such as Zoom/Teams/WeChat/OBS/screen recording software/camera App). Please exit the application that is occupying the camera first, or end the related process in the system and try again; restarting the browser/computer if necessary can usually relieve the occupation.

It could be that you are using incognito/private mode, or your browser is set to "ask every time". Please set the camera permission to "Always Allow" in the browser site settings; you can also close the incognito window and try again in the normal window.

For privacy reasons, many browsers hide the device name before granting permission. Generally, after you click "Start Preview" and allow permissions, "refresh" the device list will display a more complete name.

facingMode is a "preference" constraint, and different browsers/devices have different levels of support. It is often ignored, especially on the desktop. A safer way is to directly select the specific camera (deviceId) in the drop-down box and click "Apply and Restart".

Mirroring is often used to preview selfies more intuitively (like looking in a mirror). The "mirror display" on this page only affects the display layer; the screenshots will be based on the "real picture" (no mirroring), which is convenient for you to make objective comparison and retention.

The grid can help you place the subject in a more stable position on the screen, and also facilitate you to align the same area for comparison under different test conditions; the middle focus frame can be used as a reference for "observation focus", especially when checking the out-of-focus/breathing effect.

Average brightness (0–255) reflects the overall light and dark; dark clipping/highlight clipping indicates how many pixels fall in extremely dark (≤16) or extremely bright (≥240) areas. When the cropping ratio is significantly increased, the picture is more likely to lose details such as "black/white". Prioritize this by adjusting the lighting, avoiding strong backlight, and changing the shooting angle.

Common reasons are hand-held shake, autofocus pulling back and forth (out of focus/breathing), or insufficient light causing the shutter to slow down/noise reduction to become stronger. You can confirm by fixing the device on a table, increasing the lighting, or repeating the test on areas with high contrast details.

This means that the browser does not support or has disabled `getUserMedia`. Please use a modern browser (Chrome/Edge/Safari/Firefox) and ensure access in an HTTPS environment; some enterprise/school device policies may also disable camera-related APIs, which require administrators to release.

Taking screenshots requires that the video has entered the playable state (the picture frame has been obtained). Please "Start Preview" first and confirm that the screen appears before taking a screenshot; if there is still no response, try to stop/restart the preview or change the browser.

This page will not upload video streams or screenshots, but once you allow the browser camera permission, the browser will allow the site to request the camera when you open the page. It is recommended to only grant "Always Allow" in environments you trust, and click "Stop" and close the page when not in use.