Wordpress background-slider PHP adjustment

I am working on a self-hosted Wordpress site and am using this theme, [login to view URL] The theme allows the use of multiple fullscreen background images that fade from one to the next. The problem is that when one background image fades into the next, there is a dip in brightness during the transition. (the image gets slightly darker) Each image in the background is almost identical and I only want the subtle changes to be noticed. When the entire background dips in brightness, it interferes with this desired effect. I requested help from the author of the theme and his response was, "hi, sorry about this. this is the original design of backslider plugin, I have tried different ways to change the fade transitions but all have side effect, so there is no better ways get to the effect you want presently." Attached is an image that demonstrates the issue. Message me here if you'd like to see the site that I'm working on and I will send you the URL and the password needed to view it. Thanks