310
9.
PHOTOGRAPHY
(7) Characteristics of specimen. The beginner must learn to recognize
as soon as possible what is bad preservation and not waste time trying
to obtain good pictures of nearly worthless material.
(8) Sectioning artifact. Although most artifacts introduced by sectioning are easy to recognize, very fine order chatter may not be. It may tear
apart the tissue on such a fine scale that the picture simulates poor
preservation. One can imagine that this results from a scraping action
of the knife rather than from proper cutting. The fault may be with
the embedding material, knife angle, block size, or cutting speed.
9.6. Photographic Plates
Many investigators have been lured into a will-o'-the-wisp search for
the ideal plate to use in electron microscopy. They, of course, have been
seeking the ultimate in fine grain coupled with speed and a high contrast
response. Their quest has sometimes rested on the false assumption that
photographic emulsions respond to electron bombardment much as they
do to light. While the photographic industry has produced technological
marvels in producing a variety of films with a great range of response to
light, no such range is to be found in their response to electrons. Differences in speed and contrast are relatively minor. But for once the electron
microscopist has physical principles working to aid him rather than
battle him, for the mere fact that electrons do not penetrate appreciable
distances means that there is negligible lateral scattering within the emulsion. Therefore, image boundaries can be very sharp! This also means
that the effective layer of emulsion is extremely thin, which intrinsically
produces a great resolution as the photographic industry has lately discovered and is exploiting in films for miniature cameras. In effect, we
have had this all along. Thus, the definition of an electron image turned
out to be better than what might have been anticipated originally.
In general, an emulsion which is desirable for spectroscopy is also suitable for electron microscopy. The spectroscopist, however, often wishes
panchromatic films which simply means unnecessarily complicated darkroom procedures for an electron microscopist. A slow orthochromatic
film which can be developed with a bright safe light is all that we need.
In the United States, the Eastman Kodak Company Lantern Slide Plate
(contrast grade) has served very well. The company once published an
amusing advertisement in various scientific journals apologizing for the
9.
PHOTOGRAPHY
(7) Characteristics of specimen. The beginner must learn to recognize
as soon as possible what is bad preservation and not waste time trying
to obtain good pictures of nearly worthless material.
(8) Sectioning artifact. Although most artifacts introduced by sectioning are easy to recognize, very fine order chatter may not be. It may tear
apart the tissue on such a fine scale that the picture simulates poor
preservation. One can imagine that this results from a scraping action
of the knife rather than from proper cutting. The fault may be with
the embedding material, knife angle, block size, or cutting speed.
9.6. Photographic Plates
Many investigators have been lured into a will-o'-the-wisp search for
the ideal plate to use in electron microscopy. They, of course, have been
seeking the ultimate in fine grain coupled with speed and a high contrast
response. Their quest has sometimes rested on the false assumption that
photographic emulsions respond to electron bombardment much as they
do to light. While the photographic industry has produced technological
marvels in producing a variety of films with a great range of response to
light, no such range is to be found in their response to electrons. Differences in speed and contrast are relatively minor. But for once the electron
microscopist has physical principles working to aid him rather than
battle him, for the mere fact that electrons do not penetrate appreciable
distances means that there is negligible lateral scattering within the emulsion. Therefore, image boundaries can be very sharp! This also means
that the effective layer of emulsion is extremely thin, which intrinsically
produces a great resolution as the photographic industry has lately discovered and is exploiting in films for miniature cameras. In effect, we
have had this all along. Thus, the definition of an electron image turned
out to be better than what might have been anticipated originally.
In general, an emulsion which is desirable for spectroscopy is also suitable for electron microscopy. The spectroscopist, however, often wishes
panchromatic films which simply means unnecessarily complicated darkroom procedures for an electron microscopist. A slow orthochromatic
film which can be developed with a bright safe light is all that we need.
In the United States, the Eastman Kodak Company Lantern Slide Plate
(contrast grade) has served very well. The company once published an
amusing advertisement in various scientific journals apologizing for the