Manual calibration of android cameras

I have almost finished writing a color detector app for Android. However I am having a problem with very close shots. Both my NexusOne and Desire are unable to properly auto-focus at such lengths. I have tried pretty much all the parameters to no avail. Is it possible to let the user focus the lens?

I tried implementing the zoom trick ( move phone back a开发者_如何转开发nd zoom and then auto focus ) and while it works on the native camera app I am unable to get it working with my app.

All advice appreciated. :)

Basically u cannot focus item which are close by(Macro mode) using Nexus One or Desire or for that matter most phones. I am yet to find any phone which does though, but I am not discounting that there may be some phones :-)