If you have trouble connecting the camera or shooting photos after it is connected, go through these steps carefully from top to bottom
Camera Doesn't Connect
Check Permissions First
Make sure you've opened the Camera Settings page at least once and tapped OK on all permission popups
Verify that the Camera Settings screen shows "USB Camera: searching..." at the top-right. If it does not, scroll down this page to learn how to fix it
Make sure the app has permission to "Files and Folders": Open Settings App → Privacy → Files and Folders and ensure Booth.Events is turned on
Most Common Fix
Power down your iPad/iPhone completely, hold down the button(s), swipe to power off - then turn it back on again. This almost always fixes the issue.
Check Your Hardware
USB-C hub: If you are using a USB hub, try a direct connection between the camera and the iPad, without the hub, to rule out the hub as the issue. Camera-iPad connections put a lot of strain on a hub, which cheap hubs cannot handle.
USB cable: Try a different USB cable. If you have the cable the camera came with, try using that one.
90-degree connectors: If you're using a 90-degree angle connector, try without it as they are often the cause of the problem.
Lightning adapter: If you're using a USB-to-Lightning adapter and it's not made by Apple, try a genuine Apple part.
Check Your Memory Card
Check that the camera has a memory card in it, and format the card using the camera. Most cameras will not allow USB tethering when there's no formatted card inserted.
After formatting, take one photo on the camera so that the card is not completely empty.
If your camera has multiple memory card slots, make sure there are cards in every slot.
The camera must have a memory card in it even when it is connected to the app. The app looks for the photo on the memory card and copies it over, so without a card the camera takes the photo but has nowhere to save it (the app keeps spinning).
Formatting the card erases everything on it, so copy off anything you need first.
You can't see how much space is left on the memory card in the app at the moment. Check this on the camera itself before your event.
Check Camera Settings
Disable Wi-Fi: Some cameras like the Canon T6, T6i, T7, T7i will not allow USB tethering while Wi-Fi is enabled.
Photography mode: If your camera has separate video modes and photography modes, make sure the camera is in a photography mode. Your camera might have a physical switch for changing this.
Reset to defaults: Reset your camera to default settings. We saw a Canon T7 connect but live view would not start, after resetting, everything worked. Here's a link to reset many Canon cameras.
Update iOS
Update iOS by going to Settings App → General → Software Update.
Update Your Camera Firmware and the App
Make sure your camera is on the latest firmware from the camera maker, and that the Booth.Events app is updated from the App Store. Camera firmware updates have fixed connection and live view problems on cameras like the Canon R100. Firmware updates usually need to be done on a computer.
About Video Modes
When an external camera is connected, photos are taken with the external camera. Some cameras support taking videos and boomerangs in video mode. Others do not - the app will switch to the iPad camera automatically if needed. If you don't want the iPad camera to be used, turn off slow-mos and boomerangs in event settings.
How do I switch back to the iPad camera?
Unplug the USB camera completely.
Force quit the Booth.Events app and open it again.
When no USB camera is connected, the app uses the iPad camera.
Camera Connects, But Then Has a Problem
Are your photos sometimes coming out all-white? Check this article.
Live View Problems
Live view black, sideways, cropped or mirrored, or camera settings resetting after you reconnect? See USB Camera Live View: Black, Sideways, Mirrored or Settings Resetting.
Photos Don't Appear on iPad
If your camera takes the photo but then never shows it on the iPad screen, check that your camera is set to save JPG (not RAW) files.
You can also use JPG+RAW if your camera supports it, but the camera must save JPG.
We recommend the JPG size that matches closest to 3000 × 2000 pixels; this is often called "JPG M" or "JPG S2".
Autofocus Issues
Try turning off autofocus (usually on the lens itself, sometimes a setting on the camera). If that fixes the problem, then autofocus is the issue.
Make sure your camera's settings prioritize taking the photo on time instead of getting perfect focus (called "release priority" on some cameras).
Try increasing the amount of light and contrast: have at least one light source at 20–40 degrees rotation from your guests. This creates some shadows around the nose, eyes, and clothes that the autofocus will use to lock on.
If you want to use manual focus, see Recommended USB Camera Settings: Focus, Flash & Lighting.
Camera tries to focus again after the photo and the photo never shows up? Switch the lens or camera to manual focus (MF) and test again. If the camera can't finish focusing in time, the photo may not reach the app.
Slow Autofocus Setting
Try turning on Slow autofocus on the Camera Settings screen, and make sure your countdown timer is set to 3 seconds or longer on the Event Settings middle page. These two settings both make a difference even when you are not using autofocus on the camera.
Single Shot Mode
Check that your camera is in "Single shot mode". When not connected to the app, if you hold down the shutter button on your camera it should take only one photo, right away.
Older/Budget Friendly Cameras
Set the "USB Camera speed" to "Very Slow" as shown in the image below. Then close the event settings to make sure they are saved. Then kill and restart the app.
Getting the error, "USB camera: Error contents auth denied" ?
If you see this error: Make sure the app has permission to "Files and Folders": Open Settings App -> Privacy -> Files and Folders -> make sure Booth.Events is turned on
Sony Cameras
If using a Sony camera you must turn on "PC Remote (USB)" or "Remote Shoot (PC remote)" or "PC Remote Function" on the camera. For some cameras you need to set this before you connect the USB cable. For newer cameras you will be prompted to choose this when the connection is made with the USB cable.
Some newer Sony cameras including the A7iii and A7iv have an additional setting like "Image Save Destination" when connected to PC Remote function. This must be set to PC+Camera; if it is set to only camera then the app will not receive any photos
Having trouble finding the "Image Save Destination" menu item? Please see https://helpguide.sony.net/ilc/1650/v1/en/contents/TP0001486795.html
You must set the Priority Set in AF-S/AF-C settings to Release. If you set it to AF Priority, the app will hang or pause. The location of this setting is different for different Sony cameras, check out this video.
When the liveview is fast enough (which is the case for most modern Sony cameras) we are able to use the liveview stream for making slow-mos and boomerangs. In other cases the iPad camera will be used if necessary.
This video shows you how to do this on a Sony ZV-E10:
Camera Settings & Avoiding Blurry Photos
Recommended settings for focus, strobe flash, constant lighting and adjusting settings in the app are now in their own article: Recommended USB Camera Settings: Focus, Flash & Lighting.
Photos blurry, grainy, dark or washed out? See Why Are My Photos Blurry, Grainy, Dark or Washed Out?.