Gil - good question, the problem is that the closest focusing on the straight camera is 1cm at its widest setting which is the equivalent of a 28mm. The issue is that the lens has a very wide field of view and a depth of field which goes from the front of the frame to the back, which allows you do some great images. So you can get stuff like this...
The problem is that the camera almost ends up touching the object you are trying to take. Which is not an issue with a flower, but can start to be a problem with an insect or small creature. You may also start to have problems lighting your subject, as there is no physical room to get a light or flash in front of the camera.
Using the camera straight is not an issue and you will get some really interesting images, however, adding in close up filters allows you to move further away from your subject, be able to isolate the object in the image and increase the magnification and get the subject bigger in the picture.
I produced the following slide for a lecture I gave recently and it shows how different strength close up filters allow you to alter the working distance to your subject. So by fitting a simple +1 Dioptre filter means you can then use your camera at it longest zoom setting and focus at around 1 metre, changing to a +2 allows you to focus at around 50cm from your subject, which is good for a butterfly. The higher the number the closer you can get to your subject, the closest I can get with my normal kit is around 12.5cm with my +8 filter with that I am getting very close to my subject.
So from the above table, this is what you get from a +1.6
While this is the sort of image you would get from a +8
Hope that helps

