This is a darkfield condenser and objective set for our T670 microscopes. Both dry and oil condensers are included to cover a wide range of magnifications and numerical apertures. The dry condenser, with an NA of 0.7-0.9 is best-suited for lower-magnification objectives, typically up to 40X. The oil condenser has a maximum NA of 1.36, and is necessary for higher-magnification objectives. As well, the oil condenser will produce brighter highlights. A variable-aperture 100X objective is also included, to better control contrast at the highest magnification. Because darkfield uses oblique light explicitly, an objective lens’ numerical aperture must be significantly lower than that of the condenser to optimize contrast. The 100X lens’ built-in iris-control allows the NA to be fine-tuned for optimal results. Darkfield microscopy uses principles of light-diffraction to suppress field-illumination, while illuminating the edges of otherwise-transparent or translucent objects through the use of oblique light. This is particularly useful for quantitative analysis of low-contrast specimens. Condenser Specifications: Condenser Mount: front-loading with flange Mounting Diameter: 37mm Compatibility: 670 series compound microscopes Numerical Aperture: 0.7-0.9 (dry), 1.25-1.36 (oil) Immersion Medium: none (dry), oil (oil) Objective Specifications: Infinity-corrected Plan Achromatic Objective with Iris Magnification: 100X Numerical Aperture: 0.36-1.25 Thread Size: RMS 20mm Tube Length: infinity Immersion Medium: oil Nose: spring