Have any of you used the target brand up & up opk? I bought the 20 pack one. i tested from cd 12-18 or maybe it was cd19 and the test line was so light. it was there, my iphone camera picked it up in a picture so no need to squint, but I do know those are negative. I tested on a whim today cd 22, and to my surprise the test line was much darker than the other tests previously. It is not as dark as the control line, but not terribly far off. I am wondering if this brand of opk's just wont give you that super dark test line?