Ground glass is glass whose surface has been
ground to produce a flat but rough ( matte) finish.
Ground glass surfaces have many applications,
ranging from mere ornamentation on windows
and table glassware to scientific uses in optics
and laboratory glassware .
Uses
Photography
File:Ground glass - Graflex Speed Graphic
4x5" (about 1942).jpg
Ground glass focussing with a Graflex Speed
Graphic 4x5" camera (about 1942)
In photography, a sheet of ground glass is used
for the manual focusing in some still and motion
picture cameras , the ground-glass viewer is
inserted in the back of the camera, and the lens
opened to its widest aperture . This projects the
scene on the ground glass upside down. The
photographer focuses and composes using this
projected image, sometimes with the aid of a
magnifying glass (or loupe). In order to see the
image better, a dark cloth is used to block out
light, whence came the image of the old-time
photographer with his head stuck under a large
black cloth.
A ground glass is also used in the reflex finder of
an SLR or TLR camera.
In motion picture cameras, the ground glass is a
small, usually removable piece of transparent
glass that sits between the rotary disc shutter
and the viewfinder. The ground glass usually
contains precise markings to show the camera
operator the boundaries of the frame or the center
reticle, or any other important information.
Because the ground glass is positioned between
the mirror shutter and the viewfinder, it does not
interfere with the image reaching the film and is
therefore not recorded over the final image, but
rather serves as a reference for the camera
operator.
Ground glasses commonly serve as a framing
reference for a desired aspect ratio . Because most
films shot with spherical lenses are shot full-
frame and later masked during projection to a
more widescreen aspect ratio, it is important not
only for the operator to be able to see the
boundaries of that aspect ratio, but also for the
ground glass to be properly aligned in the camera
so that the markings are an exact representation
of the boundaries of the image recorded on film.
Lighting
Ground glass is widely used as a weather- and
heat-proof light diffuser in ambient lighting,
namely on glass covers or enclosures for lamp
fixtures, and sometimes on incandescent bulbs.
Its functions include preventing eye damage by
direct looking at lamp filament, hiding unsightly
details of the lamp and fixture without blocking its
light, and producing a softer illumination without
sharp shadows.
Chemistry
Ground glass surfaces are often found on the
glass equipment of chemical laboratories .
Glass flasks, stoppers, valves, funnels, and tubing
are often connected together by ground glass
joints , matching pairs of conical or spherical
surfaces that have been ground to a precise
shape.
Flasks and test tubes often have a small ground-
glass label area on the side. (Pencil writing on
ground glass is largely inert, rub-proof and
waterproof, but can be easily erased.)
Technical optics
Microscopes often include a ground-glass
diffusing filter to generate an even illuminated
field behind the specimen. Microscope slides are
often ground on the sides, thus softening the
edges for safer handling.
Poison
Popular belief for many centuries is that ground-
up glass (i.e., glass broken into tiny fragments)
can kill if swallowed. In fact, this is a myth, as it
is largely ineffective. [1][2]
The Guy de Maupassant short story " La
Confession " concerns a jealous girl who poisons
her older sister's suitor by inserting ground-up
glass into cake. [3]
See also
Focusing screen
Ground glass joints
Ground glass hepatocyte
Frosted glass
References
1. ^ "Pain in the Glass" . Snopes . Retrieved 5
August 2013.
2. ^ Kruszelnicki, Karl. "Ground glass kills" . Dr
Karl. ABC Science. Retrieved 5 August 2013.
3. ^ de Maupassant, Guy. "A Sister's
Confession" . Retrieved 5 August 2013.
External links
Ground glasses available from Panavision
Ground glass focusing with the Speed Graphic
Ground Glass focusing screens available from
hopfglass
This article was originally based on " Ground glass
back " in Camerapedia, retrieved at an unknown
date under the GNU Free Documentation License.
Read in another language
This page is available in 3 languages
Čeština
Français
Slovenčina
ground to produce a flat but rough ( matte) finish.
Ground glass surfaces have many applications,
ranging from mere ornamentation on windows
and table glassware to scientific uses in optics
and laboratory glassware .
Uses
Photography
File:Ground glass - Graflex Speed Graphic
4x5" (about 1942).jpg
Ground glass focussing with a Graflex Speed
Graphic 4x5" camera (about 1942)
In photography, a sheet of ground glass is used
for the manual focusing in some still and motion
picture cameras , the ground-glass viewer is
inserted in the back of the camera, and the lens
opened to its widest aperture . This projects the
scene on the ground glass upside down. The
photographer focuses and composes using this
projected image, sometimes with the aid of a
magnifying glass (or loupe). In order to see the
image better, a dark cloth is used to block out
light, whence came the image of the old-time
photographer with his head stuck under a large
black cloth.
A ground glass is also used in the reflex finder of
an SLR or TLR camera.
In motion picture cameras, the ground glass is a
small, usually removable piece of transparent
glass that sits between the rotary disc shutter
and the viewfinder. The ground glass usually
contains precise markings to show the camera
operator the boundaries of the frame or the center
reticle, or any other important information.
Because the ground glass is positioned between
the mirror shutter and the viewfinder, it does not
interfere with the image reaching the film and is
therefore not recorded over the final image, but
rather serves as a reference for the camera
operator.
Ground glasses commonly serve as a framing
reference for a desired aspect ratio . Because most
films shot with spherical lenses are shot full-
frame and later masked during projection to a
more widescreen aspect ratio, it is important not
only for the operator to be able to see the
boundaries of that aspect ratio, but also for the
ground glass to be properly aligned in the camera
so that the markings are an exact representation
of the boundaries of the image recorded on film.
Lighting
Ground glass is widely used as a weather- and
heat-proof light diffuser in ambient lighting,
namely on glass covers or enclosures for lamp
fixtures, and sometimes on incandescent bulbs.
Its functions include preventing eye damage by
direct looking at lamp filament, hiding unsightly
details of the lamp and fixture without blocking its
light, and producing a softer illumination without
sharp shadows.
Chemistry
Ground glass surfaces are often found on the
glass equipment of chemical laboratories .
Glass flasks, stoppers, valves, funnels, and tubing
are often connected together by ground glass
joints , matching pairs of conical or spherical
surfaces that have been ground to a precise
shape.
Flasks and test tubes often have a small ground-
glass label area on the side. (Pencil writing on
ground glass is largely inert, rub-proof and
waterproof, but can be easily erased.)
Technical optics
Microscopes often include a ground-glass
diffusing filter to generate an even illuminated
field behind the specimen. Microscope slides are
often ground on the sides, thus softening the
edges for safer handling.
Poison
Popular belief for many centuries is that ground-
up glass (i.e., glass broken into tiny fragments)
can kill if swallowed. In fact, this is a myth, as it
is largely ineffective. [1][2]
The Guy de Maupassant short story " La
Confession " concerns a jealous girl who poisons
her older sister's suitor by inserting ground-up
glass into cake. [3]
See also
Focusing screen
Ground glass joints
Ground glass hepatocyte
Frosted glass
References
1. ^ "Pain in the Glass" . Snopes . Retrieved 5
August 2013.
2. ^ Kruszelnicki, Karl. "Ground glass kills" . Dr
Karl. ABC Science. Retrieved 5 August 2013.
3. ^ de Maupassant, Guy. "A Sister's
Confession" . Retrieved 5 August 2013.
External links
Ground glasses available from Panavision
Ground glass focusing with the Speed Graphic
Ground Glass focusing screens available from
hopfglass
This article was originally based on " Ground glass
back " in Camerapedia, retrieved at an unknown
date under the GNU Free Documentation License.
Read in another language
This page is available in 3 languages
Čeština
Français
Slovenčina
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