The darkfield condenser allows you to render detail in specimens that would otherwise be transparent. Using principles of light-diffraction to suppress field-illumination, the condenser illuminates edges of cells, microorganisms, and other objects. This is particularly useful for live blood analysis. This darkfield condenser is designed for use with immersion oil. The 1.36 maximum numerical aperture will accommodate higher-magnification objective lenses with numerical apertures up to 1.25. However, it is recommended to use objective lenses with numerical apertures at or below 1.0 for true darkfield. Objective lenses designed for darkfield, such as those with iris-control like our PA100X-IRIS, are recommended for high magnifications. As well, magnifications of 10X and below may experience vignetting, in which case a dry condenser is preferable. The condenser has two centering screws for properly aligning the illumination halo. This allows you to optimize the lighting on microscopes that do not have centerable condenser-holders. This condenser is designed to work with compound microscopes with a 37mm bottom-mount condenser holder. Compatible models include: B340, T340, B400, T400, B450, T450, B460, B490, T490, B590, T590, B600, T600, B680, T680, M220, M600 Condenser Mount: 37mm bottom mount Model Compatibility: B340, T340, B400, T400, B450, T450, B460, B490, T490, B590, T590, B600, T600, B680, T680, M220, M600 Numerical Aperture: 1.25-1.36 Immersion Medium: oil Centerable Optics: yes