A few days ago I asked (in the midst of another thread) what the effect of the 10mm extension tube had on normal applications. I can't remember what thread it was, but I've done some testing. Not scientific, but a somewhat illuminating (at least to me) nonetheless. I have always used extension tubes for macro work and never questioned what they could do for more normal applications. Someone had used the 10mm tube with the Oly 75-300mm lens for some "off-nominal" application and I decided (after asking what the focal length range was) that I could test my P100-300 in the same way. So I did. Because I had started my testing indoors in the evening (which was not very successful), I had cranked the ISO up to 26500 (as far as it would go). I was shooting in Aperture priority mode. Each of these images were sharpened in my normal sharpening process (which isn't anything special) but I won't go into those details here. This first shot is auto-focused at about 2 1/4 feet with the p100-300 set at 300mm and the 10mm extension tube. At about 1.5 feet, the lens would not focus on the green metal table top and instead focused on the wooden deck floor about 3 feet away. This next one is focused on the little frog about 8-10 feet away (the frog is a little guy with an abdomen about an inch and a half across). Everything else is the same (300mm, 10mm tube). Finally test image #3 was the most surprising image. This was also taken at 300mm using the 10mm tube, but the subject was about 30 feet away! The lens would not AF at another subject about 50 feet away.