Lens: Cheap 4x/0.10 achromat microscope objective
Vintage: Current
Lens Mount: RMS (20 mm x 0.8 mm)
Needed Adapters: RMS mount adapters come in various forms. Some can be
found to directly connect to a specific lens mount as this mount is also shared by
many small bellows lenses. I use an RMS to T-mount adapter and then a T-mount
to Nikon f-mount adapter. T-mount adapters are available for virtually all camera
lens mounts.
found to directly connect to a specific lens mount as this mount is also shared by
many small bellows lenses. I use an RMS to T-mount adapter and then a T-mount
to Nikon f-mount adapter. T-mount adapters are available for virtually all camera
lens mounts.
Preferred Mounting: Normal (not reversed)
Filter Thread: None
Controls: There are no controls on this objective.
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Corner Sharpness vs magnification:
This objective shows very fuzzy corners. This is
what you get with a cheap achromatic objective.
These are made to be sharp in the center. To
keep the designs cheap and simple they forego
the corner sharpness. If you want sharper
corners, get a planar objective (called "plan").
They will tend to cost a little more.
I wouldn't recommend going much below 4:1
magnification with this objective as the corner
performance just worsens more.
This objective shows very fuzzy corners. This is
what you get with a cheap achromatic objective.
These are made to be sharp in the center. To
keep the designs cheap and simple they forego
the corner sharpness. If you want sharper
corners, get a planar objective (called "plan").
They will tend to cost a little more.
I wouldn't recommend going much below 4:1
magnification with this objective as the corner
performance just worsens more.
Sharpness and Resolution vs Magnification:
Despite the inexpensive nature of this objective,
the central sharpness and resolution is actually
pretty good. It will resolve details down to about
1.7 um at 7:5:1 magnification.
Despite the inexpensive nature of this objective,
the central sharpness and resolution is actually
pretty good. It will resolve details down to about
1.7 um at 7:5:1 magnification.
Street Price: $20 - $35 new
Chromatic Aberration: This lens show minimal color fringing in the center
(about 0.10 - 0.25 pixels) and mild on the periphery (0.7- 1.1 pixels). Color
fringes are another factor that microscope objectives tend to have depending
upon the price of the objective. The most expensive, apochromatic objectives
have the least, while the least expensive tend to have quite a lot. This
objective actually does pretty well for its price.
(about 0.10 - 0.25 pixels) and mild on the periphery (0.7- 1.1 pixels). Color
fringes are another factor that microscope objectives tend to have depending
upon the price of the objective. The most expensive, apochromatic objectives
have the least, while the least expensive tend to have quite a lot. This
objective actually does pretty well for its price.
Image Contrast: Image contrast is good for this magnification range, but
less than its more expensive name-brand bretheren.
less than its more expensive name-brand bretheren.
Flare: This lens shows significant flare when used with reflected light owing
to the reflective inner surface of the cap that goes on the end of the objective.
This flare can be be easily remedied by just unscrewing the cap. (see picture
above)
to the reflective inner surface of the cap that goes on the end of the objective.
This flare can be be easily remedied by just unscrewing the cap. (see picture
above)
Conclusion: This is an objective that works reasonably well as a bellows
lens. The sharpness and resolution are quite good for the objective
magnification range of about 4:1 to 8:1.
The corner performance is where the cost cutting is done for this objective.
With a single image, the corners are very fuzzy. The situation improves quite
a bit when you use focus stacking to make images. The inherent field
curvature of this lens can be compensated for by the focus stacking process
and the corners actually look decent when done.
This lens also lacks a bit in image contrast compared to more expensive
objectives, but the images look OK.
The color correction is actually pretty good for this lens and it doesn't show
large fringes in the center or on the periphery.
This lens does suffer from significant flare although that can mostly fixed by
removing the cap on the end of the objective. You could also put flocking on
the inside of the cap and leave it on.
Its low price is tempting, but you will likely be better served by finding a planar
objective for a few dollars more.
lens. The sharpness and resolution are quite good for the objective
magnification range of about 4:1 to 8:1.
The corner performance is where the cost cutting is done for this objective.
With a single image, the corners are very fuzzy. The situation improves quite
a bit when you use focus stacking to make images. The inherent field
curvature of this lens can be compensated for by the focus stacking process
and the corners actually look decent when done.
This lens also lacks a bit in image contrast compared to more expensive
objectives, but the images look OK.
The color correction is actually pretty good for this lens and it doesn't show
large fringes in the center or on the periphery.
This lens does suffer from significant flare although that can mostly fixed by
removing the cap on the end of the objective. You could also put flocking on
the inside of the cap and leave it on.
Its low price is tempting, but you will likely be better served by finding a planar
objective for a few dollars more.
Basic Function: Requires a bellows for setting focus and magnification. This objective works best when
the end cap is removed (see image below). With the end cap on there is significant flare from the inside
of the cap when using reflected light.
the end cap is removed (see image below). With the end cap on there is significant flare from the inside
of the cap when using reflected light.
Appearance:
Aperture: The aperture is fixed at a numerical aperture of 0.10 - corresponds to about f/4
Image Samples:
About 4.2:1 magnification, focus stack of 33 images, resized: The corner performance on this
focus stacked image is actually better than you would expect by the poor corner performance. This
improvement is related to the fact that the lens has significant field curvature. Field curvature is
where the plane of sharp focus is not flat (while the detector is). This can be corrected with a more
expensive design. This aberration can be seen in images fairly easily. If the center is in focus, the
edges won't be. If the edges are in decent focus, the center won't be. A single image will always
look bad. A focus stacked image will help to compensate for the field curvature (as in the image
below).
focus stacked image is actually better than you would expect by the poor corner performance. This
improvement is related to the fact that the lens has significant field curvature. Field curvature is
where the plane of sharp focus is not flat (while the detector is). This can be corrected with a more
expensive design. This aberration can be seen in images fairly easily. If the center is in focus, the
edges won't be. If the edges are in decent focus, the center won't be. A single image will always
look bad. A focus stacked image will help to compensate for the field curvature (as in the image
below).
About 4.2:1 magnification, 1 to 1 crop of single
source image from above:
This lens shows very good pixel level detail at 4:1 in
the center of the field.
source image from above:
This lens shows very good pixel level detail at 4:1 in
the center of the field.
About 6.5:1 magnification, focus stack of 36 images, resized: The corners are a little better at
this magnification.
this magnification.
About 6:1 magnification, 1 to 1 crop of a single
source image from above:
This image shows good detail for the magnification.
source image from above:
This image shows good detail for the magnification.
Performance: Sharpness vs Magnification:
This is a new graph that I recently constructed. I
have 4 lines that represent levels of performance
from outstanding (top) to fair (bottom). This
shows where this lens fit into the hierarchy that I
have created.
The cheap 4x achromat shows very good to good
sharpness performance across its magnification
range.
This is a new graph that I recently constructed. I
have 4 lines that represent levels of performance
from outstanding (top) to fair (bottom). This
shows where this lens fit into the hierarchy that I
have created.
The cheap 4x achromat shows very good to good
sharpness performance across its magnification
range.
Performance: Resolution vs Magnification:
This is a new graph that I recently constructed. I
have 4 lines that represent levels of performance
from outstanding (top) to fair (bottom). This
shows where this lens fit into the hierarchy that I
have created.
The cheap 4x achromat shows good to fair
resolution performance across its magnification
range.
This is a new graph that I recently constructed. I
have 4 lines that represent levels of performance
from outstanding (top) to fair (bottom). This
shows where this lens fit into the hierarchy that I
have created.
The cheap 4x achromat shows good to fair
resolution performance across its magnification
range.
