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Lower resolution image target produces BETTER rating

February 14, 2018 - 12:59am #1

Hello, this doesn't make much sense to me, maybe you could explain it better than me.


I'm working on an image target, the image is black and white and I'm working inside Adobe Illustrator. Since my preferred image print size is in A4 paper, it made sense to me to export in 3508x2480 resolution (300dpi). When I uploaded it in Vuforia target manager I got 4 stars rating. I tried adding more elements in the image to increase rating (although from what I was seeing there already were quite a lot of features in the image) but 4 stars was the best I got.


After some experimenting, I exported once (by mistake to be honest) in 72dpi, only 596x842. And the exact same image got a 5 star rating. Is there any logical explanation to this?


I should say that I used 100 as Width in the target manager.

Lower resolution image target produces BETTER rating

March 3, 2018 - 4:58am #2

Hey, we've faced the same issue in the recent past


Unfortunately, I can't give you a concrete reason, just a guess:

Vuforia seems to scale down and make grayscale any image that's uploaded to it before actually analysing it. It may be that the way it does that is not as good as how Illustrator (and Photoshop and other image editing software in general) go about it, which may translate to lower ratings.

On the other hand, it may be that by providing a higher resolution image (or rather, one closer to the physical target size), you actually get a "truer" result. Which would mean your 4 stars are closer to reality.


Did you perceive a difference in the actual tracking of the target? Did the 5 stars target perform better? It'd be interesting to test this with a more extreme case - eg. a 2 stars target that becomes 5 stars when downscaling before sending to Vuforia.

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