Friend, here is the solution to the problem of brightness or excessive light.

I had this same problem, and I did not find any solution even here in vuforia, everything indicated problems of light or some problem of the Voforia API.

After a lot of research with the solution, this is a problem of scale of the imageTarget, which is adapted to the resolusion of the marker that is imported and therefore the ARcamera does the same. If the scale is very high where x, y, z exceeds 500. when creating the apk and proving in android it happens that they look very bright when the camera moves away from the target. EYE, this does not happen when tested directly on UNITY.

Just down the scale 1 of ImageTarget

X = 1; Y = 1; Z = 1

Then the Camera also make some adjustments.

Near = 0.01

Far = 5 

You might want to post it in the Wish List as well:

https://developer.vuforia.com/forum/general-discussion/wish-list

Even without a manual exposure adjustment capability, iOS default camera gives higher exposure on AE.

The iOS Camera app benefits from Auto-Exposure (AE) which is why the image may appear brighter in a darker setting

As I wrote in the original post, I turned this on outside of Vuforia. While results improved, it's still far too dim.

I just tested this with Vuforia 4 with nothing in the scene except the ARCamera prefab, not sure if there is an improvement, but I can't notice one.

I know you have a lot of things to implement, but I think providing a way to increase the exposure with an AE lock should be prioriotized, because if the camera can't see, then all the other features, however awesome may they be, are irrelevant.

The iOS Camera app benefits from Auto-Exposure (AE) which is why the image may appear brighter in a darker setting. Vuforia takes ownership of the camera, but doesn't do any AE adjustments (perhaps AE dynamic lightening/darkening of camera feed could negatively impact feature point tracking in the target). If you tap an area within the iOS Camera app, it will adjust the focus and exposure based of the point where you tapped. In the Vuforia samples, tapping the screen adjusts the overall focus and is not influenced by the tap point position. While the Vuforia API offers settings for Auto-Focus (AF), it doesn't offer any for AE.

https://developer.vuforia.com/resources/api/unity/class_camera_device

FocusMode {
  FOCUS_MODE_NORMAL,
  FOCUS_MODE_TRIGGERAUTO,
  FOCUS_MODE_CONTINUOUSAUTO,
  FOCUS_MODE_INFINITY,
  FOCUS_MODE_MACRO
}

Related: The iOS Camera app has an "AE/AF Lock" feature to disable the AE. This article discusses it:

http://www.igeeksblog.com/how-to-adjust-separate-focus-and-exposure-setting-on-iphone-ipad-camera-app-in-ios-8/

I also tested an iPad Mini Retina with iOS 8.1.2 and saw normal results similar to my testing with iPad 3 with 7.1.2. I've attached a screenshot taken in a room with dimmed lighting and you can see a slight difference in the iOS Camera app using AE to adjust the result.

Thank you for responding. 

Are you able to reproduce the issue using our iOS sample apps?

 

Yes, I attached a screenshot from the UDT sample app. 

 The brightness and exposure look the same. 

It appears that you are in a very well-lit room, in which case this is a non-issue. Things in a dimmer environment are not as lovely, unfortunatelly. Scanning movie posters in a theater, for example, is very difficult, whereas the default camera provides a *much* better higher exposure and brightness. 

You're also not running the latest version of iOS, so that's another variable. 

I've attached a side-by-side comparison image of two screen captures from an iPad 3 with iOS 7.1.2. The left is from the Camera app and the right from the Cloud Reco sample app. The brightness and exposure look the same. It appears from your dark screenshot that there's some additional image elements overlayed on top of the app background. Are you able to reproduce the issue using our iOS sample apps?

Bump:

Please look at the attached screenshot! This is an iOS-wide issue, tested on four different Apple devices, that makes all of Vuforia unusable. What good is Computer Vision if it can't see?