20X100 25x100 Binocular

Bill Meyers wrote in message ...
On this basis, my Oberwerk 12 x60s are noticeably vignetted, and my Oberwerk 15 x
70s are a bit vignetted.
Bill Meyers

lal_truckee wrote:

Chris1011 wrote:

You can easily see whether your binos are fully illuminated and not stopped
down. Place your eye at the very edge of the front element and look down into
the prism. If you can see the entire eyepiece exit pupil from one edge to the
other, it is fully illuminated to the full aperture of the front element. If
you can see only part of the exit pupil, it is internally vignetted to some
degree.



As Bill replies, on this basis, I find almost every binocular I own
would fit you criteria for vignetted. I don't believe this is an
accurate test. This would indicate both my 10x70 and 16x70 Fujinons
are about 30% to 40% vignetted. So would my Pentax, my Swift,
Minolta, Nikon, Oberwerk and Orion. That is not correct. In fact I
own about 15 binoculars. I have not found a single one that would
pass this test.

I have seen the description of this test written by Roland Christen
(almost word for word as described above). I think there needs to be
some explanation. In every case, the baffles will prevent you from
seeing the full edge of the prism. However in no case was the exit
pupil smaller than the aperture magnification would indicate. To me,
that means the full aperture is in use.

You want to know if your binocs are vignetted, measure your exit
pupils.

edz

Bill Meyers wrote in message ...
On this basis, my Oberwerk 12 x60s are noticeably vignetted, and my Oberwerk 15 x
70s are a bit vignetted.
Bill Meyers

lal_truckee wrote:

Chris1011 wrote:

You can easily see whether your binos are fully illuminated and not stopped
down. Place your eye at the very edge of the front element and look down into
the prism. If you can see the entire eyepiece exit pupil from one edge to the
other, it is fully illuminated to the full aperture of the front element. If
you can see only part of the exit pupil, it is internally vignetted to some
degree.



As Bill replies, on this basis, I find almost every binocular I own
would fit you criteria for vignetted. I don't believe this is an
accurate test. This would indicate both my 10x70 and 16x70 Fujinons
are about 30% to 40% vignetted. So would my Pentax, my Swift,
Minolta, Nikon, Oberwerk and Orion. That is not correct. In fact I
own about 15 binoculars. I have not found a single one that would
pass this test.

I have seen the description of this test written by Roland Christen
(almost word for word as described above). I think there needs to be
some explanation. In every case, the baffles will prevent you from
seeing the full edge of the prism. However in no case was the exit
pupil smaller than the aperture magnification would indicate. To me,
that means the full aperture is in use.

You want to know if your binocs are vignetted, measure your exit
pupils.

edz

Ed wrote:
As Bill replies, on this basis, I find almost every binocular I own
would fit you criteria for vignetted. I don't believe this is an
accurate test. This would indicate both my 10x70 and 16x70 Fujinons
are about 30% to 40% vignetted. So would my Pentax, my Swift,
Minolta, Nikon, Oberwerk and Orion. That is not correct. In fact I
own about 15 binoculars. I have not found a single one that would
pass this test.

I have seen the description of this test written by Roland Christen
(almost word for word as described above). I think there needs to be
some explanation. In every case, the baffles will prevent you from
seeing the full edge of the prism. However in no case was the exit
pupil smaller than the aperture magnification would indicate. To me,
that means the full aperture is in use.

You want to know if your binocs are vignetted, measure your exit
pupils.

Uh, wouldn't that just tell you whether or not the *center* of field
was vignetted? That is, wouldn't it only tell you that your fully
illuminated field was non-zero?

The point of putting your eye at the edge is presumably to evaluate
the degree of vignetting at an extreme off-axis angle (in AFOV). That
seems like the right test to me. It *is* hard to satisfy. I can see
legitimate reasons for not making sure it's satisfied, just as I can
see legitimate reasons for not making sure the entire field stop of
a 41 Pan in a Newtonian, for instance. Just because it's a legitimate
thing to do does not mean it doesn't happen, though.

Binoculars are almost exclusively visual instruments. I'd be more
concerned about correcting the edge of the field than I would be about
making sure that edge was fully illuminated.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

Ed wrote:
As Bill replies, on this basis, I find almost every binocular I own
would fit you criteria for vignetted. I don't believe this is an
accurate test. This would indicate both my 10x70 and 16x70 Fujinons
are about 30% to 40% vignetted. So would my Pentax, my Swift,
Minolta, Nikon, Oberwerk and Orion. That is not correct. In fact I
own about 15 binoculars. I have not found a single one that would
pass this test.

I have seen the description of this test written by Roland Christen
(almost word for word as described above). I think there needs to be
some explanation. In every case, the baffles will prevent you from
seeing the full edge of the prism. However in no case was the exit
pupil smaller than the aperture magnification would indicate. To me,
that means the full aperture is in use.

You want to know if your binocs are vignetted, measure your exit
pupils.

Uh, wouldn't that just tell you whether or not the *center* of field
was vignetted? That is, wouldn't it only tell you that your fully
illuminated field was non-zero?

The point of putting your eye at the edge is presumably to evaluate
the degree of vignetting at an extreme off-axis angle (in AFOV). That
seems like the right test to me. It *is* hard to satisfy. I can see
legitimate reasons for not making sure it's satisfied, just as I can
see legitimate reasons for not making sure the entire field stop of
a 41 Pan in a Newtonian, for instance. Just because it's a legitimate
thing to do does not mean it doesn't happen, though.

Binoculars are almost exclusively visual instruments. I'd be more
concerned about correcting the edge of the field than I would be about
making sure that edge was fully illuminated.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

The point of putting your eye at the edge is presumably to evaluate
the degree of vignetting at an extreme off-axis angle (in AFOV).

The point of putting your eye at the edge of the front aperture is that you can
very quickly evaluate whether the center and BOTH the edges of the exit pupil
are fully illuminated. If that is true, then the entire field is fully
illuminated.

If you can see only one edge and center from the periphery of the front
aperture, then the field is only partially illuminated by the full front
aperture.

If you cannot see the CENTER of the exit pupil from the edge of the front lens,
but can see one edge, then the binos are NOT fully illuminated in the center of
the field. They are somewhat vignetted. In this case, to determine the actual
aperture of the binos in the center of the field, just place a series of
cutouts with different apertures over the front until you find the one which
allows you to just begin to see the center of the exit pupil. That would be the
aperture that contributes to the image in the center of your eyepiece field.

Continue with smaller apertures until you can see the entire exit pupil from
the edge of the aperture. That would be the size of the front lens that
illuminates the edge of your eyepiece field.

Sounds complicated but really isn't.

Roland Christen

The point of putting your eye at the edge is presumably to evaluate
the degree of vignetting at an extreme off-axis angle (in AFOV).

The point of putting your eye at the edge of the front aperture is that you can
very quickly evaluate whether the center and BOTH the edges of the exit pupil
are fully illuminated. If that is true, then the entire field is fully
illuminated.

If you can see only one edge and center from the periphery of the front
aperture, then the field is only partially illuminated by the full front
aperture.

If you cannot see the CENTER of the exit pupil from the edge of the front lens,
but can see one edge, then the binos are NOT fully illuminated in the center of
the field. They are somewhat vignetted. In this case, to determine the actual
aperture of the binos in the center of the field, just place a series of
cutouts with different apertures over the front until you find the one which
allows you to just begin to see the center of the exit pupil. That would be the
aperture that contributes to the image in the center of your eyepiece field.

Continue with smaller apertures until you can see the entire exit pupil from
the edge of the aperture. That would be the size of the front lens that
illuminates the edge of your eyepiece field.

Sounds complicated but really isn't.

Roland Christen

Ï "Chris1011" Ýãñáøå óôï ìÞíõìá
...

The point of putting your eye at the edge is presumably to evaluate
the degree of vignetting at an extreme off-axis angle (in AFOV).

The point of putting your eye at the edge of the front aperture is that
you can
very quickly evaluate whether the center and BOTH the edges of the exit
pupil
are fully illuminated. If that is true, then the entire field is fully
illuminated.

If you can see only one edge and center from the periphery of the front
aperture, then the field is only partially illuminated by the full front
aperture.

If you cannot see the CENTER of the exit pupil from the edge of the front
lens,
but can see one edge, then the binos are NOT fully illuminated in the
center of
the field. They are somewhat vignetted. In this case, to determine the
actual
aperture of the binos in the center of the field, just place a series of
cutouts with different apertures over the front until you find the one
which
allows you to just begin to see the center of the exit pupil. That would
be the
aperture that contributes to the image in the center of your eyepiece
field.

Continue with smaller apertures until you can see the entire exit pupil
from
the edge of the aperture. That would be the size of the front lens that
illuminates the edge of your eyepiece field.

Sounds complicated but really isn't.

Thanks for the explanation Roland. I can see the center of the exit pupil on
my Apogee 20x100, along with one side of the exit pupil, but not the side
corresponding to the side from which I am looking down to, which according
to your explanation means that the center is fully illuminated but the edges
are not.

The exit pupil from the edge looks exactly like Venus' shape at its current
stage.

The question though is, why would one manufacture the optics as such, if one
could simply use a smaller full apperture unvignetted?
It doesn't make much sense to me. Any further explanations?

Roland Christen
--
Ioannis Galidakis
http://users.forthnet.gr/ath/jgal/
------------------------------------------
Eventually, _everything_ is understandable

Ï "Chris1011" Ýãñáøå óôï ìÞíõìá
...

The point of putting your eye at the edge is presumably to evaluate
the degree of vignetting at an extreme off-axis angle (in AFOV).

The point of putting your eye at the edge of the front aperture is that
you can
very quickly evaluate whether the center and BOTH the edges of the exit
pupil
are fully illuminated. If that is true, then the entire field is fully
illuminated.

If you can see only one edge and center from the periphery of the front
aperture, then the field is only partially illuminated by the full front
aperture.

If you cannot see the CENTER of the exit pupil from the edge of the front
lens,
but can see one edge, then the binos are NOT fully illuminated in the
center of
the field. They are somewhat vignetted. In this case, to determine the
actual
aperture of the binos in the center of the field, just place a series of
cutouts with different apertures over the front until you find the one
which
allows you to just begin to see the center of the exit pupil. That would
be the
aperture that contributes to the image in the center of your eyepiece
field.

Continue with smaller apertures until you can see the entire exit pupil
from
the edge of the aperture. That would be the size of the front lens that
illuminates the edge of your eyepiece field.

Sounds complicated but really isn't.

Thanks for the explanation Roland. I can see the center of the exit pupil on
my Apogee 20x100, along with one side of the exit pupil, but not the side
corresponding to the side from which I am looking down to, which according
to your explanation means that the center is fully illuminated but the edges
are not.

The exit pupil from the edge looks exactly like Venus' shape at its current
stage.

The question though is, why would one manufacture the optics as such, if one
could simply use a smaller full apperture unvignetted?
It doesn't make much sense to me. Any further explanations?

Roland Christen
--
Ioannis Galidakis
http://users.forthnet.gr/ath/jgal/
------------------------------------------
Eventually, _everything_ is understandable

The question though is, why would one manufacture the optics as such, if one
could simply use a smaller full apperture unvignetted?

You get more money for a supposedly "larger" front aperture, regardless if it's
fully used or not.

Roland Christen

The question though is, why would one manufacture the optics as such, if one
could simply use a smaller full apperture unvignetted?

You get more money for a supposedly "larger" front aperture, regardless if it's
fully used or not.

Roland Christen