Darkfield condensers allow 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 set includes a dry darkfield condenser for lower magnifications, an oil darkfield condenser for higher magnifications, and a specialized 100X objective lens with a built-in iris to control its aperture for increased contrast. The dry condenser works with objective lenses with numerical apertures below 0.9, including most lenses up to 40X. For higher magnifications, the oil condenser provides optimal brightness and contrast. By placing immersion oil between the oil condenser and the specimen slide, high numerical apertures can be achieved with maximum brightness. While this will work with 100X objective lenses, the darkfield effect loses contrast with increased aperture. A special 100X plan-achromatic darkfield objective lens is included, with the ability to lower its NA through the use of an internal iris. An adjustment collar on the lens allows you to easily adjust the aperture until optimal darkfield is achieved. This set 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 Model Compatibility: B340, T340, B400, T400, B450, T450, B460, B490, T490, B590, T590, B600, T600, B680, T680, M220, M600 Dry Condenser: --Mount: 37mm bottom mount --Numerical Aperture: 0.7-0.9 --Immersion Medium: none --Centerable Optics: yes Oil Condenser: --Mount: 37mm bottom mount --Numerical Aperture: 1.25-1.36 --Immersion Medium: oil --Centerable Optics: yes Objective Lens: --Magnification 100X --Optical System: finite --Mount: 20.32mm RMS --Mechanical Tube Length: 160mm --Numerical Aperture: 0.31 to 1.25 --Immersion Medium: oil --Corrections: plan-achromatic --Cover-glass Thickness: 0.17mm --Nosecone: spring-loaded Packing List: One dry darkfield condenser One oil darkfield condenser One oil darkfield objective lens