Microscopes equipped specifically for fluorescence illumination often have illuminated reticles in the eyepiece, which allow the microscopist to visualize a photomicrography grating superimposed over faintly visible specimens positioned against a very dark background. Instructions for operation of the tutorial appear below the applet window.
The applet initializes with the specimen and reticle focus and illumination values randomly chosen. Use the Specimen Focus slider to focus the image of the specimen, then switch to the Reticle Focus slider to do the same for the photomicrography reticle. The Lamp Intensity slider can be used to increase or decrease specimen brightness. Select between specimens using the Choose A Specimen pull-down menu.
Both Olympus and Nikon provide reticles that offer a choice of colors in their high-end microscopes. Microscopists can choose between a red or yellow illuminated reticle. The red reticle has the advantage of maintaining the dark adaptation of the observer's eye and provides excellent contrast when viewed over blue and green secondary fluorescence. For red fluorescence and when simultaneous phase contrast or DIC are used, the yellow reticle should be selected to maximize contrast. Some manufacturers offer a focusing telescope with illuminated framing reticle that attaches as a focusing telescope and allows viewing of the film frame dimensions over the dark field.