Subject: Photo Glossary
Date: 27 Nov 1995 01:44:43 -0500
Sender: root@newsbf02.news.aol.com
Reply-To: fishfotojr@aol.com (FishFotoJr)

This is a list of photographic terms complied from various publications,
technical sheets and personal knowlegde pertaining to shooting and
hardwear.


Ai:The name given to lenses produced between 1977 and 1981.  they can be
mounted on an Ai accepting body without aligning a particular f-stop and
meter coupling prong (the rabbit ears) to reduce the time taken lens
change (amd more acurate metering)

AIS: These lenses have been produced since 1981 for both manual focus
lenses, AIS-P and AF lenses (since 1985).  The internal mechanism for
controlling the iris diaphram is differnet to Ai lens types.  It allows
what we term a linear control of the diaphram.  This is necessary for
Program and Shutter Priority operation (with Nikon bodies with this
feature , barring AF bodies) AIS lenses are distingushed by the smallest
f-stop marked in orange.  On the rear of the mount, an index depending on
it;s depth, enables manual AIS lenses to inform the body of it's focal
length.  AF lenses and AIS-P optics use CPU technology to provide this
information to the cameras CPU.

AIS-P: Only one Nikkor is AIS-P, the Nikkor 500f4.  The 500f4-P is a
manual focus lens with a CPU incorportaed inside the mount and lens to
transfer the same information to the body as an AF lens.

Ambient Light: The term used to describe a constant source of lighting,
rather than an instant light, such as a strobe.  When using a strobe for
lighting this light is then refered to as available light, ie: light like
tungston, sodium vapor and of course day light.

Aperture: The opening in th diaphram of a lens, through which light passes
to reach the film plane.

Aperture Priority:  Works in reverse of Shutter Priority.  Aperture
Priority enable a particular aperture to be set on the lens, and have the
camera adjust the shutter speed to match the set aperture and thus setting
the proper exposer.

Auto Flash:  The first form of controlled measurement for flash exposer. 
A sensor on the face of a strobe responds to flash illumination as it
returns towards the camera from the subject.  When enough has returned,
the flash units's output is reached.

Backlighting:  The term used to describe a subject that has a strong light
source source illuminating it from behind

Balance Fill Flash:  Is the correct term when the flash illumination is
controlled to illuminate a subject, while the aperture and shutter speed
values expose the backround correctlywith ambient light.  This allows a
balance in exposer between electronic flash and ambient light.

Centre Weighted: The term given to a light measurement system bias to the
centre of the frame area.

CPU:  Central Processing Unit (computer processing unit)

Cybernetic Synch:  This term refers to the electronic control of the
shutter , for proper synchronisation with TTL compatible speedlights.  A
cyber is an electronic component that performs a task , in this case
shutter - flash  synchronisation.

Exposer Factor: Refers to an increase in exposer greater than is normally
required for correct exposer.  Ths a used when usinf filters, bellows or
extreme shadows and you have to add extra light to get a corerct exposer.

Fill Flash: The strength of the flash unit's output is controlled to
enable it' output to be kept at a strength lower than the effective  that
the ambient light will have on a scene.  This will reduce the contrast
because the flash will illuminate the shadow areas.

Flash Tube: The unit which contains the inert gas which ignites to provide
the electronic flash.

Guide Number: The given numbers indicates the actual strength of flash
illumination.  It is quoted in meters or feet.  This number is usually
dervived at by using a normal(50mm) lens, and with ISO 100 film.

Incident Light Reading: Is made usualy with a seperate out of camera light
meter.  The measuring surface is pointed towards the light source, to
measure the strength of the lighting on the subject, not bounced or
reflected light.

ISO: The newer standard to term for ASA (American Standards Association)
is ISO (Internations Standards Organization.  The films ISO is it's given
speed, or ability to take in light.  The lower the number the finer
grained the film and the less light the film will accep, meaning you must
add light to the film plane by either opening the aperture or slowing the
exposer time.  ISO is measured in stops, for expamle ISO25 is 6 stops
slower that ISO 800, in terms of exposer this means a 1/15 exposer becomes
a 1/500 exposer.

Kelvin: The standard unit of measurement for colour charactistics of a
light source.  Given tempertures in photography are given in Kelvin.

LCD: Liquid Crystal Display.  Most Nikon and Canon top deck LCDs and
speedlight LCDs are twisted nematic LCDs.

Martix: A light measurement system and computer program develped to
interpert the scene's brightness level and make adjustments in order to
obtain a technically corrct exposer.

MPT: Micro Processing Technlogy, the term used in computer and electronic
fields to describe the electronic components, such a CPUs which evaluate
or process data.

Multi-Flash: The use of two or more strobes fired at the same time,
sychronised, so all have an effect on the exposer.

Realtime: Instantaneous action performed by the camer, lens and strobe.

Reat Curtain Flash Synch: When the flash is fired at the end of the
exposer to allow for ambient light, and then freeze a given subject in the
end position.  

Red-Eye:  Red-eye is caused by  when the flash is reflected back from the
retina of the eye.

Shutter Priority:  Shutter Priority is the oposite of Apertute Priority. 
You set the desired shutter speed, and the camera body chooses the correct
aperture to allow for that shutter speed and correct exposer time.  

Speedlight: brand name of a flash by Nikon and Canon.  Speedlight has
become like saying "Coke" or "Pampers" to some when refering to a cola or
diapers.

Spot Metering: refers to a measurment system from  a very small central
point in an image.  A true spot reading is a 1-degree meausrement, most
all cameras have a larger area for spot metering.

Strobe Flash(re-peteing flash):  Stroboscopic flash is a series of rapid
flashes that is used to record movemet consecutively on one frame.

Synchronisation:  When a speedlight fires correctly with the shutter
speed, thus firing whe the entize shutter curtain is open lighting the
entire frame.

TTL:  Through the Lens, when a subject is metered through the lens, or
when a TTL flash meters the subject through the lens to derive the proper
exposer or the scene.

Vignette:  When the frame shows a reduction in full frame viewing at the
edges.

Working Distance:  The distance between the front of the lens and the
subject.
Steven E. Frischling
Freelance News Photographer
NYPD Working Press #0067

Too young to be respected; Too old to not be taken seriously; INVINCIBLE!;
Fear was just a word in the dictionary; Life was a right, not a gift;
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