Phasecontrastmicroscopeapplication

The angle indicating the width of the field included in the photo is called the "angle of view." A wide-angle lens has a wide angle of view and a telephoto lens has a narrow angle of view.

With a zoom lens, when you turn on macro mode and move as close as possible while still keeping the subject in focus, the minimum distance to the subject and the size of the subject in the frame will differ depending on whether the lens is at a wide-angle or telephoto zoom position. With a wide-angle setting you may be too close and with a telephoto setting you may be too far away so adjust the focal length to find the one that makes it easiest to take the shots you want.

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A conversion lens is attached to a lens to enable it to take photos with a wider angle or stronger telephoto magnification.

The distance from the center of the lens to the image focal point (=image sensor surface) is known as the focal length. It is expressed in millimeter (mm) units. A lens with a short focal length is a wide-angle lens and one with a long focal length is a telephoto lens.

Attaching a 0.75x wide conversion lens to a 28 mm lens gives an angle of view equivalent to a 21 mm ultra wide-angle lens.

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A typical phase contrast image has a neutral background and surrounding with varying contrast where light is altered by the specimen (Figure 1). Two very common effects seen in a phase contrast image are halo and shade-off patterns. These occur when the infinite-conjugate focal point does not match for the specimen and background. Although these are common and expected in phase contrast images, they diminish the appearances of details. In general, a bright phase contrast halo is typically visible at a boundary between strong and weak specimen features. These halos are evident due to the circular phase-retarding rings. Specialized objectives, known as apodizing phase contrast objectives, are manufactured to reduce this phenomenon.

Even if the focal lengths of the lenses of two digital cameras are the same, the angle of view can vary depending on the size of the image sensor used in each. To make it easier to understand angle of view, focal length is often expressed as "__ mm equivalent," which means it has been converted to the 35 mm film camera format that has been historically the most common. Here on this site also, we state focal lengths that are converted into 35 mm film camera format.

Knowledge Center/ Application Notes/ Microscopy Application Notes/ Optical Microscopy Application: Phase Contrast

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This is a lens used for close-up photography. A macro lens can shoot from a distance closer to the subject than a regular lens. The GXR interchangeable unit camera system has a camera unit with a 50 mm macro lens. Link to more information on GXR camera unit

Phase contrast was first utilized and described in 1934 by Frits Zernike. This optical microscopy technique enhances the contrast of transparent specimens, yielding high-contrast images of living cells, microorganisms, and other samples. The main advantage of the phase contrast technique is that living cells and tissues do not need to be killed, fixed, stained, or prepared in any way and can, in turn, be examined in their natural state. Analyzing and recording the dynamics of intricate biological processes becomes very easy with phase contrast optical microscopy.

Attaching a 1.88x teleconversion lens to a 72 mm lens gives an angle of view equivalent to a 135 mm medium telephoto lens.

Additional optical microscopy applications include brightfield illumination, darkfield illumination, fluorescence, and differential interference contrast.

* The GXR interchangeable unit camera system has camera units with a fixed focal length lens and camera units with a zoom lens.

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The phase contrast technique translates extremely tiny variations in phase into a noticeable and corresponding amplitude change, and is evident in the difference of contrast in Figure 1. The most important concept of the phase contrast microscope design is the isolation of wavefronts, both surround (undiffracted) and diffracted, that arise from the specimen. To differentiate intensity profiles between a specimen and its surroundings, the undeviated light must be reduced and the phase retarded by a quarter-wave retardance. A brightfield illumination microscope can be upgraded to a brightfield-phase microscope with the introduction of two components to the optical train. For additional information on the brightfield technique, please read Optical Microscopy Application: Brightfield Illumination.