Notes on Recording Micrographs
1. Micrographs may be recorded by either automatic or manual exposure. |
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2. The automatic exposure (active when the SHUTTER button is illuminated) should only be used for bright field images. Dark field images and diffraction patterns will not usually expose correctly if you attempt to use automatic exposure. Some users have developed a way of using the automatic exposure setting to estimate the exposure of diffraction patterns (and/or dark field images). Such a system will vary from specimen to specimen and user to user so there are no hard and fast rules. The best rule for recording diffraction patterns and dark field images is to bracket several exposures. |
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3. The automatic exposure system measures the electron current that is incident on the screen and calculates the exposure assuming that the image covers the whole screen. |
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4. If the small screen is in position, the metering system will calculate the exposure based on the illumination on the small screen. If your specimen is not of uniform contrast, it may be better to locate your feature of interest on the small screen and let the microscope determine the exposure from the small screen. |
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5. Manual exposure is selected when the SHUTTER button is in the released position and it is not illuminated. Manual exposure times are selected using the EXP TIME rocker switch above the SHUTTER button. |
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6. If you wish to record the image you are viewing on the computer monitor onto film, you may find it convenient to simply press the FOCUS (small screen) button. The main screen will lower and the small viewing (or focus) screen will be inserted. Ensure that the SHUTTER button is selected, thus enabling the automatic exposure system to read the exposure for the area that you have been examining. |
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7. When you have selected the area you wish to photograph, set the exposure value, manually or automatically, and press the PHOTO button once. |
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8. The microscope advances a plate under the viewing screen; the PHOTO button light will now be on. Note that it is advisable to leave the FILM ADVANCE button in the manual position. The green AUTO light should be off. If you use the AUTO position, there is always a plate left under the screen. This plate is wasted when you raise the screen to use the Gatan camera. |
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9. Press the PHOTO button a second time. This exposes the plate. The small green LED above the PHOTO button will be illuminated while the exposure is taking place. |
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10. During this process the information field (film number, scale bar or camera length and voltage, and so on) is also written on to the film. |
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11. Upon completion of the exposure the plate will be retracted and drop into the exposed plate container. The PHOTO button light will now be off. |
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12. If you wish to make multiple exposures you should press the PHOTO button during the exposure. This will disable the plate withdrawal system and allow you to expose another image or diffraction pattern on the same plate. Pressing the PHOTO button during the second exposure allows you to record three exposures on one plate. You may make as many multiple exposures as you wish, simply by pushing the PHOTO button each time you expose the plate. |
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