Thursday 7 October 2010

The fundamental dilemma of magnification.

Even low power magnification can be a really useful technique for intense seeing.  Magnification reveals to our naked eye new levels of detail of an object or scene.  A simple example of magnification is shown in the Figure below.  Here a low power magnifying glass (2 x) shows part of the surface of a page of text, at a higher magnification than we could see otherwise. 

However, as a simple consequence of the design of the magnifying glass only the region of the text that is seen through the magnifying glass is at higher magnification.  The physical edge of the magnifier therefore limits our view of the complete object. We see more clearly in the higher magnification observation window, but in total we see less of the text.

The single fundamental act of using a magnifiying glass therefore introduces two separate consequences; [1] New insight and resolution within the observation window [2] an artificial observation window that represents a geometrical sampling of the whole object.

This is the fundamental dilemma of magnification.

Note that this dilemma  is also true, but perhaps less obviously,  for all practical optical instruments, such as cameras, microscopes and telescopes. By design they all have to impose an artificially limited observation window on the magnified view of the object or scene.

The choices we make to try and deal with this dilemma are at the heart  of the artistic and scientific techniques that rely on magnification or focusing of any sort.