Nick, that's a classic. I've not noticed that before either but now I'm going to look for it. It certainly provides some food for thought. Cheers, Paul

I also saw that Nick. Check the link below. What I found was that if it was a very hot day with little wind, then it left a sunburnt spot. On cooler days it sometimes just left a slightly bleached area on the leaves. Sorry, I should have taken pictures and updated this post.

Japie

Here is a link that might be useful: Reflected sunlight