Canon EF 90-300 mm f/ 4.5-5.6 Lens 部件
Tele-Apotessar
®
T
* f/2.8 - 300 mm
In general, the correction of longitudinal chromatic
aberration in camera lenses is confined to the
superimposition of the images for two colours of
light. The aberrations occurring with all other
colours produce the "secondary spectrum" which
increases in proportion to the focal length. The
secondary spectrum and the lateral chromatic
aberration (appearing in the image field as colour
fringes on contrasty edges) limit the optical
performance of a telephoto lens made up of
classical glass. Apart from crystal materials, the
modern fluophosphate types of glass also offer the
possibility of drastically reducing residual
achromatism.
In the 300 mm TeIe-Apotessar
aberration in camera lenses is confined to the
superimposition of the images for two colours of
light. The aberrations occurring with all other
colours produce the "secondary spectrum" which
increases in proportion to the focal length. The
secondary spectrum and the lateral chromatic
aberration (appearing in the image field as colour
fringes on contrasty edges) limit the optical
performance of a telephoto lens made up of
classical glass. Apart from crystal materials, the
modern fluophosphate types of glass also offer the
possibility of drastically reducing residual
achromatism.
In the 300 mm TeIe-Apotessar
®
T
* f/2.8 lens this
glass type, with its extreme optical properties, has
been used for two elements.
been used for two elements.
The result is superior image quality. The pictures are
extremely sharp and brilliant.
The name Apotessar indicates the excellent
correction of chromatic aberration.
For focusing the Tele-Apotessar
extremely sharp and brilliant.
The name Apotessar indicates the excellent
correction of chromatic aberration.
For focusing the Tele-Apotessar
®
T
* lens, a group
in the lens is moved (internal focusing). The
advantages of this principle over the usual shift of
the total system are easy to see: constant length of
the lens and virtually constant location of the centre
of gravity during focusing; improved ease of motion
and operation of the focusing ring; the focusing
helicoid has to move only a light group and hence
does not have to withstand the pressure of the
weight of the entire lens.
Another point to note is that the image quality is
still very good at minimum focusing distance.
advantages of this principle over the usual shift of
the total system are easy to see: constant length of
the lens and virtually constant location of the centre
of gravity during focusing; improved ease of motion
and operation of the focusing ring; the focusing
helicoid has to move only a light group and hence
does not have to withstand the pressure of the
weight of the entire lens.
Another point to note is that the image quality is
still very good at minimum focusing distance.
Cat. No. of lens:
10 45 33
Focusing range:
∞
to 3.5 m
Number of elements:
7, (+ filter)
internal focusing
Number of groups:
6, (+ filter)
Entrance pupil*:
Max. aperture*:
f/2.8
Position:
446.7 mm behind the first lens vertex
Focal length*:
300.6 mm
Diameter:
102.2 mm
Negative size:
24 x 36 mm
Exit pupil*:
Angular field 2w*:
8.2º diagonal
Position:
36.3 mm in front of the last lens vertex
Lens mount:
focusing mount with bayonet;
Diameter:
37.7 mm
TTL metering either at full aperture or in
Position of principal planes*:
stopped-down position.
H:
121.1 mm in front of the first lens vertex
Built-in lens hood.
H':
12.7 mm in front of the first lens vertex
Aperture scale:
2.8 - 4 - 5.6 - 8 - 11 - 16 - 22
Back focal distance*:
67.7 mm
Filter connection:
insertable filter
Distance between first and
Weight:
approx. 2,730 g
last lens vertex:
220.1 mm
* at
∞