Darkfield Microscopes
To optimize, first try stopping down the field diaphragm to get the best contrast between background and specimen. Try to match the size of the occulting disk to the field diameter, so that the edge of the disk is just outside the field of veiw - smaller disks are appropriate for higher power objectives. Vertically, the disk should be a close to the condenser as possible, to make the contrast the greatest. On microscopes with built-in dark field equipment, the view is so impressive because the occulting disk is built into the condenser - very close and focused. After testing the set-up this way, a stand might be rigged to fit under the microscope, so the slide can be placed in position without holding it. Something that 'grabs' the condenser and supports the occulting disks would be ideal. However, when a sample is placed on the stage it appears bright against a dark background. It is similar to back-lighting an object that may be the same color as the background it sits aga