From what I've read and seen it appears to be best to increase sharpness to +1. When -1 is chosen the internal processing will apply noise reduction filters to the footage which has been a possible known cause for having soft spots in random points of the frame. This link shows a good comparison of what it looks like before and after these adjustments. It's also noted in the video that he applies noise reducing filters from Neat (https://www.neatvideo.com/) This filter does have a free trial so you can apply it to your footage, although the trial limits it's use to a 720P frame size for maximum of 30min, and adds a watermark. This will give you an idea as to weather or not you want to purchase the full version for approx. $74. From my initial trial tests, it seems more than worth it. This software allows you to build profiles for each of your capturing devices, as well as for different iso's for each device. It does an excellent job as far as I can tell. Hope this info helps.