What causes an Estimated Image Quality value >1?

[skj]

I am currently assessing the ability of Photoscan to produce successful models from underwater images collected in turbid waters.  I emailed tech support to get some technical guidance on how the "Estimated Image Quality" tool calculates/measures image quality and received a pretty vague answer that it somehow gives you information about image sharpness.  So, I am still questioning the validity of this tool for estimating image quality.

Can anyone provide me more detailed insight into how the image quality is calculated?  Also, what causes values of great than 1?

[Alexey Pasumansky]

Hello skupfner,

The estimated quality values can be really above 1 in some cases, for example, if there is an ultra-sharp contrast border (for test you can just "feed" the image drawn in Paint with white and black halves, saved without image compression).

The current method of the quality estimation is a kind of comparison of the contrast gradients in the most peculiar areas of the source photos - for the originals and pictures with the Gaussian blur filter applied. The output value provides a certain measure of the sharpness of the borders in the peculiar areas on the images. Higher value means sharper borders.