Lens: Pentax 100 mm f/4 bellows
Vintage: about 1970
Lens Mount: M42 x 1
Needed Adapters: M42 to F-mount, easily found on eBay
Preferred Mounting: Normal (not reversed)
Filter Thread: 49 mm
Controls: This lens only has two controls - aperture preset and aperture setting. The outer
preset ring allows you to set the final position of the aperture, while the aperture setting ring
allows you to adjust the aperture smoothly between wide-open (for focusing) and the chosen
preset (for taking the picture).
preset ring allows you to set the final position of the aperture, while the aperture setting ring
allows you to adjust the aperture smoothly between wide-open (for focusing) and the chosen
preset (for taking the picture).
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Resolution vs Aperture: The lens has f/9.4 as
its sharpest and highest resolving aperture while
many of its competitors are sharpest at about f/8.
As a general rule, you will get better resolution
long as it is the sharpest).
For me this means that I would use f/9.4 when
shooting images to get the sharpest and most
highly detailed images.
its sharpest and highest resolving aperture while
many of its competitors are sharpest at about f/8.
As a general rule, you will get better resolution
long as it is the sharpest).
For me this means that I would use f/9.4 when
shooting images to get the sharpest and most
highly detailed images.
Corner Sharpness vs Aperture: There is
moderate fuzziness on the periphery at larger
apertures, but the corner sharpness improves as
the aperture is closed down. At the sharpest
aperture of f/9.4, the corners are very nearly as
sharp as the center - just what you want with a
macro lens.
Testing done on a Nikon D200, a DX format
digital camera (APS-C). On a full-frame camera
the performance would tend be a little worse.
Note: I would say that any number under 10% will
only be faintly visible on an image.
moderate fuzziness on the periphery at larger
apertures, but the corner sharpness improves as
the aperture is closed down. At the sharpest
aperture of f/9.4, the corners are very nearly as
sharp as the center - just what you want with a
macro lens.
Testing done on a Nikon D200, a DX format
digital camera (APS-C). On a full-frame camera
the performance would tend be a little worse.
Note: I would say that any number under 10% will
only be faintly visible on an image.
Sharpness and Resolution vs Magnification:
This lens' resolving power in the center of the
field is slightly lower than its competitors of similar
focal length. Compared to modern macro lenses
of similar focal length, the resolution is
significantly decreased. The MTF50 of this lens
at 1:1 magnification is about 800 lp/ph while a
good modern macro lens will be anywhere from
1000-1200 lp/ph at the same magnification.
These numbers only apply to a DX format Nikon
D200. With a full-frame detector or a higher
megapixel camera, the numbers would tend be
slightly higher.
As an example: If you are shooting an image at a
magnification of about 0.5x or 1:2 (will just about
fit a silver dollar full screen on a D200), you can
expect to get about 1050 "sharp" pixels across
the height of the image and no more than about
2200 pixels of real detail in the image across the
hieght of the picture. These numbers will improve
somewhat with the use of image sharpening in
the photo editor (or in-camera when shooting jpg)
This lens' resolving power in the center of the
field is slightly lower than its competitors of similar
focal length. Compared to modern macro lenses
of similar focal length, the resolution is
significantly decreased. The MTF50 of this lens
at 1:1 magnification is about 800 lp/ph while a
good modern macro lens will be anywhere from
1000-1200 lp/ph at the same magnification.
These numbers only apply to a DX format Nikon
D200. With a full-frame detector or a higher
megapixel camera, the numbers would tend be
slightly higher.
As an example: If you are shooting an image at a
magnification of about 0.5x or 1:2 (will just about
fit a silver dollar full screen on a D200), you can
expect to get about 1050 "sharp" pixels across
the height of the image and no more than about
2200 pixels of real detail in the image across the
hieght of the picture. These numbers will improve
somewhat with the use of image sharpening in
the photo editor (or in-camera when shooting jpg)
Street Price: ~$150 in good used condition
Chromatic Aberration: This lens show minimal color fringing in the center
(about 0.10 pixel, mainly axial) and mild in the periphery (0.80 - 1.0 pixel,
mainly lateral). Anything below 1.0 pixel is good.
(about 0.10 pixel, mainly axial) and mild in the periphery (0.80 - 1.0 pixel,
mainly lateral). Anything below 1.0 pixel is good.
Image Contrast: Image contrast is good, but not spectacular for this
magnification range.
magnification range.
Flare: No significant flare is evident during lens testing
Conclusion: This is a bellows lens that performs well, but less than typical
modern 100 mm or 105 mm macro lenses - likely a symptom of the age and
simplicity of the design. As seen in the above images, it is fully capable of
taking high-quality images across its usable magnification range. As with most
bellows lenses, this lens shows very good corner sharpness and little
chromatic aberration.
This lens is useful to get more working distance and for use at lower
magnification. Shorter focal length lenses will almost invariably have better
resolution capabilities. That being said, modern macro lenses will almost
always outperform bellows lenses in this focal length and magnification
range, although that difference is small when looking at actual images.
modern 100 mm or 105 mm macro lenses - likely a symptom of the age and
simplicity of the design. As seen in the above images, it is fully capable of
taking high-quality images across its usable magnification range. As with most
bellows lenses, this lens shows very good corner sharpness and little
chromatic aberration.
This lens is useful to get more working distance and for use at lower
magnification. Shorter focal length lenses will almost invariably have better
resolution capabilities. That being said, modern macro lenses will almost
always outperform bellows lenses in this focal length and magnification
range, although that difference is small when looking at actual images.
Basic Function: Requires a bellows for setting focus and magnification.
Appearance:
Aperture: 8 blades, varies in shape from a near-circle to an 8-sided star, to an octagon as it is closed.
Image Samples:
About 1:3 magnification, f/9.4, cropped horizontally and resized
About 1:3 magnification, f/9.4, 1 to 1 crop:
This image shows just a trace of unsharpness
compared to its more modern macro lenses when
viewed at full size, but not much. When viewed at a
smaller size such as the above picture, the images
are virtually indistinguishable.
This image shows just a trace of unsharpness
compared to its more modern macro lenses when
viewed at full size, but not much. When viewed at a
smaller size such as the above picture, the images
are virtually indistinguishable.
About 1:1 magnification, f/9.4, resized
About 1:1 magnification, f/9.4, 1 to 1 crop:
Again there isn't much difference between the pixel
level detail of this lens and its newer competitors such
as the Nikon 105VR.
Again there isn't much difference between the pixel
level detail of this lens and its newer competitors such
as the Nikon 105VR.
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 Pentax 100mm shows sharpness
performance that varies from good at the low-end
of magnification to poor 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 Pentax 100mm shows sharpness
performance that varies from good at the low-end
of magnification to poor 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 Pentax 100mm shows resolution
performance that varies from good at the low-end
of magnification to poor 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 Pentax 100mm shows resolution
performance that varies from good at the low-end
of magnification to poor at the high-end.
