5
Iris diaphragm should not be used to control the brightness of illumination. Iris diaphragms are designed to
help achieve high resolution of specimen and provide contrast in the image. Smaller apertures will deliver
higher contrast to image. However, closing aperture too much will reduce resolution. Experimentation is
the best method of determining the correct opening of diaphragm. Some suggested openings for iris
diaphragm are:
OBJECTIVE
DIAPHRAGM OPENING
4x
From fully closed to 1/8 open
10x
1/8 to 1/4 open
40x
1/4 to 1/2 open
100x
1/2 to 3/4 open
G. Usage of blue filter (one 32mm O.D. transparent blue filter has been provided with your microscope)
a) Placing a filter into the optical path will absorb some of the light from the illuminator base, limiting the
light output. Filters should only be used when they help enhance the image.
b) The fluorescent bulb in your microscope produces daylight type of illumination. Use of the transparent
blue filter will produce a slightly blue light, and blue filter does not need to be used with this microscope
under normal circumstances.
c) To insert filter, grasp filter holder knob and swing out filter holder, insert filter into slot provided and
swing filter into optical path.
d) When handling the filter do not touch lens surfaces as fingerprints and smudges will result in poor
images.
H. Changing magnification.
a) Rotate revolving nosepiece to position 10x objective into optical path.
b) This microscope has been parfocalized, which allows changes from one objective to another while
requiring only a slight adjustment of the fine focus controls.
c) When changing to the 40x and 100x objective lens, care must be exercised when positioning these
lenses into the optical path, in order to prevent damaging the front lens element and specimen slide.
d) In order to obtain maximum resolution of the 100x oil immersion lens, it is necessary to apply
immersion oil between the coverglass of slide and front lens of the objective.
(1) Use of a very small amount of immersion oil is required.
(2) All air bubbles must be removed from between lens and slide by gently rotating nosepiece back and
forth.
Objective Specification Chart
Objective
N.A.
Color Code
Ring
Field of
View
Working
Distance
Magnification with
WF10X eyepiece
Din 4X
0.10
Red
4.5mm
26.4mm
40X
Din 10X
0.25
Yellow
1.8mm
5.5mm
100X
Din 40X
0.65
Blue
0.45mm
0.48mm
400X
Models 156-S and 157 only
Din 100X
1.25
White
0.18mm
0.06mm
1000X
I.
When finished viewing, all parts that come in contact with oil must be cleaned. Failure to do so could
permanently damage the 100x oil immersion objective lens. Use Windex to clean immersion oil off lens
surfaces is recommended.
