First of all I'm very proud of Nokia for bringing us such wonderful free accessibility features.
Together with Nokia's Audiobook player this application has brought more innovation into my low vision lifestyle than any other product in the past year or two.
It still needs work and will probably not replace my Amigo digital magnifier, but it's very handy.
I'm not sure what the technical limitations are, but I'd like to suggest a possible improvement.
Many digital magnifiers rather than trying to achieve perfect focus in a color image, have a 2 color mode, that uses a high degree of sharpening. the two colors don't have to be black and white, they can be different combinations, such as yellow on black or yellow on blue and others... to suite different eye conditions and user preference.
Since were mostly dealing with text here a color image isn't always necessary, and a highly sharpened 2 tone image can really increase legibility and perhaps negate the need to achieve perfect focus.
I've seen digital magnifiers that use a fixed lens and yet achieve a perfectly sharp image of text in 2 tone color.