Lens: Leica Photar 25mm f/2 bellows lens
Vintage: current
Lens Mount: RMS mount
Needed Adapters: This lens is fairly easy to adapt via a standard RMS adapter. I use an RMS to
t-mount adapter and a t-mount to nikon F adapter.
t-mount adapter and a t-mount to nikon F adapter.
Preferred Mounting: Normal.
Filter Thread: None.
Controls: This lens only has an aperture control.
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Resolution vs Aperture:
The sharpest and most resolving aperture is
about f/3.3 (half way between f/2.8 and f/4).
Since there are no aperture detents, you will
need to eyeball the aperture setting.
The sharpest and most resolving aperture is
about f/3.3 (half way between f/2.8 and f/4).
Since there are no aperture detents, you will
need to eyeball the aperture setting.
Corner Sharpness vs Aperture:
The corner sharpness is OK above an aperture
of f/3.3. If you want really sharp corners at lower
magnification, you may choose to use f/4. You
will give up a little resolution in the process, but
the sharpness is nearly equal to f/3.3.
I was a little disappointed by the less than stellar
corner sharpness of this lens.
(Testing done at 4:1 magnification. Numbers at
each aperture setting will tend to improve as the
magnification is decreased.)
The corner sharpness is OK above an aperture
of f/3.3. If you want really sharp corners at lower
magnification, you may choose to use f/4. You
will give up a little resolution in the process, but
the sharpness is nearly equal to f/3.3.
I was a little disappointed by the less than stellar
corner sharpness of this lens.
(Testing done at 4:1 magnification. Numbers at
each aperture setting will tend to improve as the
magnification is decreased.)
Sharpness and Resolution vs Magnification:
This lens shows extremely good sharpness and
resolution across its usable magnification range
of 2.3x - 9.4x. As bellows lenses go, I haven't
found one that outperforms this lens in center
sharpness and resolution across this
magnification range. It is one of only 2 lenses
that I have tested so far that have a MTF50
above 1000 lw/ph above a magnification of 3:1.
Corner sharpness is a little below average for
bellows lenses. It is not so hot at lower
magnifications and pretty good at higher
magnifications.
.
This lens shows extremely good sharpness and
resolution across its usable magnification range
of 2.3x - 9.4x. As bellows lenses go, I haven't
found one that outperforms this lens in center
sharpness and resolution across this
magnification range. It is one of only 2 lenses
that I have tested so far that have a MTF50
above 1000 lw/ph above a magnification of 3:1.
Corner sharpness is a little below average for
bellows lenses. It is not so hot at lower
magnifications and pretty good at higher
magnifications.
.
Street Price: ~$500 - $900 on eBay.
Chromatic Aberration: This lens show minimal color fringing in the center
(about 0.05 - 0.40 pixel) and moderate/severe on the periphery (1.30 - 3.80
pixels). Anything below 1.0 pixel is good.
(about 0.05 - 0.40 pixel) and moderate/severe on the periphery (1.30 - 3.80
pixels). Anything below 1.0 pixel is good.
Image Contrast: Image contrast is good across the magnification range.
Flare: No significant flare is evident during lens testing
Conclusion:
This is an expensive bellows lens and at least for central sharpness and resolution, performs as
you would expect a lens of this caliber - top of the heap. It performs at its best at an aperture of
about f/3.3 - half way between f/2.8 and f/4.
The main downfall of this lens is its corner sharpness, varying from not-so-hot at lower
magnification to good at higher magnification. Even though the corner sharpness isn't the greatest,
it isn't particularly noticeable on images. If you have problems with it, it is easy to bump the aperture
up a notch to f/4 and it will get noticeably better.
Chromatic aberration is also so-so on the periphery, but that goes along with the suboptimal corner
sharpness. Again, this is not particularly visible on normal images.
It has a usable magnification range from a little over 2:1 to about 9:1 on my bellows - a good range
for coin close-ups. The working distance is limited, but typical for the focal length.
It's main competitors that can produce similar sharpness and resolution numbers are the Canon
20/3.5 bellows and Olympus 20/2 bellows. Note that these two lenses are shorter focal length and
will tend to have even less working distance than this lens. They are also limited to a higher
magnification range due to their shorter focal length. The only way to improve upon these numbers
is to go to a microscope objective, and even then you will not improve by much unless you go to a
Nikon Plan APO 4x.
This is an expensive bellows lens and at least for central sharpness and resolution, performs as
you would expect a lens of this caliber - top of the heap. It performs at its best at an aperture of
about f/3.3 - half way between f/2.8 and f/4.
The main downfall of this lens is its corner sharpness, varying from not-so-hot at lower
magnification to good at higher magnification. Even though the corner sharpness isn't the greatest,
it isn't particularly noticeable on images. If you have problems with it, it is easy to bump the aperture
up a notch to f/4 and it will get noticeably better.
Chromatic aberration is also so-so on the periphery, but that goes along with the suboptimal corner
sharpness. Again, this is not particularly visible on normal images.
It has a usable magnification range from a little over 2:1 to about 9:1 on my bellows - a good range
for coin close-ups. The working distance is limited, but typical for the focal length.
It's main competitors that can produce similar sharpness and resolution numbers are the Canon
20/3.5 bellows and Olympus 20/2 bellows. Note that these two lenses are shorter focal length and
will tend to have even less working distance than this lens. They are also limited to a higher
magnification range due to their shorter focal length. The only way to improve upon these numbers
is to go to a microscope objective, and even then you will not improve by much unless you go to a
Nikon Plan APO 4x.
Basic Function: Requires extension tubes or bellows to focus.
Appearance:
Aperture: 6 blades.
Image Samples:
About 3.3:1 magnification, f/3.3, focus stack of 42 images, resized: The corners only show a very slight softness, so in real
life imaging, the corner sharpness isn't all bad.
life imaging, the corner sharpness isn't all bad.
About 3.3:1 magnification, f/3.3, 1 to 1 crop of a
source image from above:
Very good pixel level detail.
source image from above:
Very good pixel level detail.
About 7:1, f/3.3, focus stack of 25 images, resized:
About 7:1 magnification, f/3.3, 1 to 1 crop of a
single source image from above:
Again, very good detail for the magnification.
single source image from above:
Again, very good detail for the magnification.
Distortion: There is no visible distortion on the image.
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 Photar 25mm has sharpness performance
varying from outstanding at the low-end of
magnification to very good at the high-end.
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 Photar 25mm has sharpness performance
varying from outstanding at the low-end of
magnification to very good at the high-end.
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 Photar 25mm shows resolution performance
that varies from outstanding at low magnification
to good/fair at the high-end.
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 Photar 25mm shows resolution performance
that varies from outstanding at low magnification
to good/fair at the high-end.
