I first saw this F when I was doing the D week - so I went back this week... and I'm so glad I did. This is one of the clearest and best letters I've found yet, and stands out boldly even without editing and cropping. I'm also especially glad that it's not an image that could just as easily be an E that's been cropped down. That would have been easy. Any of last week's images could be turned into a reasonable F with only a little adjustment.
The two below are from a visit I made to a library that I used to work in which is shortly to close to be reopened. It's very strange walking through seeing the almost empty shelves. Some areas still have a reasonable, if depleted, stock but others are bizzarely bare.
I'm expecting G week to be especially challenging. I've found one possible image already, but it's not as good as I'd like. I thought my way through the alphabet and I figure if I can work out this week the next worryingly difficult one is Q. So wish me luck!