Lighting. SDMs are usually fitted with lamp situated below a ground glass or opaque plastic stage. The transparency of this stage affects the visibility of fine detail. Heavily opaque stages will scatter light and mask fine detail. Viewing fine detail may seem like a good thing, but not always: If you are trying to clearly see the shape of the valves only, the appearance of unnecessary detail can be distracting (see examples). In addition to the lamp CMs usually have sub-stage condensers with iris diaphragms, which allows greater control over lighting.
Colour balance. The lighting systems on budget microscopes may give a strong orange hue to the final picture. To combat this, use a blue filter between the lamp and stage. Digital users can additionally set the camera’s white balance setting and make final adjustments in programs such as Adobe Photoshop (see examples).
Vignetting (darkening of the edges). This can be caused by microscope’s eye piece or sub-stage lighting. To combat the former, zoom in the camera lens - the effective magnification will increase and image quality may suffer. Sub-stage lighting problems can be reduced by opening the iris diaphragm (if fitted), though this may reduce contrast and render fine detail invisible; and by ensuring that the bulb is fitted centrally and not shifted to one side of its chamber.
Focusing. For digital users, the camera linked to a TV rather than relying on the camera’s monitor will prove very useful. It is usually best to set the camera’s to infinity and set the focus via the microscope’s controls.
Image enhancement (see examples)