I wanted to post the pics of my opks this cycle. I ovulate all over the place, sometimes CD15, sometimes not until CD22. This was a late cycle. I started testing at CD14 and ended up finally getting a positive at CD20. Most of my tests you couldn't see a line, but some you could see a faint line after a while. It was hard to figure out what was what. As ovulation came closer, they started getting darker but not until after 10 minutes (more like 30). Then the ones closest to O finally turned dark (still don't think they were as dark as or darker than the test line) pretty quickly.
I got three good positives. One Fri night, one Sat morning and one Sat night.
I read the instructions online and they say not to use FMU and to test between 10am and 8pm. I got my first real positive about 11:45pm on Fri night. I got my second positive using FMU about 7:15am on Sat morning. So, for me, my tests seem to get gradually darker all day until late and then are a very real positive and then they stay positive for about 24 hours.
Here's the picture of all of them. As you can see they go from light to dark and the last one is light again (Sun morning). A couple of them have weird marks through them. I hope this helps someone out there using the internet cheapies

BTW, we BD Fri, Sat and Sun. Hope we caught it!!