Whenever i zoom in print composer it jumps either in or out in steps not smoothly. I can not zoom progressively neither can i choose an area by using the magnifier. I am working on a map of islands and they are either represented very small in a large mass of water or the outer islands are not visible anymore. It must be possible to exactly define the area that i want to represent in print composer. How do i do this?
You can also hold Ctrl while zooming to zoom by smaller amounts.
When you select the map item, you can specify the scale and extents. When I make maps I usually set where I am mapping in the centre of QGIS (not the composer), then in composer use the 'Set to map canvas extent'.
This will centre the print composer on where you want it, then just play with the scale and hit the 'Update preview' button every time you alter it. This gives you a bit more control than using the mouse scroll wheel.