| Abstract: | Single electrons of the energies used in transmission electron micrography can render developable one or more emulsion grains. From this fact the following deductions can be made. - (a). Photographic contrast in an electron micrograph is a function of the mean density only.
- (b). The signal/noise ratio in an electron micrograph improves with increasing exposure, irrespective of the means adopted to enable an increased exposure to be used.
- (c). If the exposure of the specimen is limited to some maximum then the visibility of noise-limited detail in prints representing a given total magnification is independent of the negative material used in the microscope.
Experimental tests based largely on electron micrographs are presented which provide good support for these deductions. It is generally concluded that the behaviour patterns examined in this work should always be considered when limitations are being encountered in the image quality of electron micrographs. |
