Now, lately i been having issues trying to bring back my SD15 to life. The main problem is that it has back focusing. 

So i used the 1.5 mm Allen key to clockwise the screw that is found nearest to the sensor location after the mirror is up.

Problem is that there is no good way to test the focusing once u tweak it, using rules, printed texts and books placed in different depth all yield inconsistent results..

I was surprised to discover this article that is PERFECT. It has a chart that you don’t even need to print, in fact u must not print, you just open it up on your LCD/LED monitor and you shoot at it with your camera and it will tell you how accurate your focus is.

The chart is not some text chart or those that gives you a similar optometrist kinda test, its a constructed chart that somehow shows up only clearly when your sensor focusing is correct.

Please head on down the link below and do your test.

http://www.northlight-images.co.uk/article_pages/cameras/1ds3_af_micoadjustment.html