Jump to content


Photo

A Wow and a Humm

  • Please log in to reply
30 replies to this topic

#1 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 43429
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 12 February 2013 - 06:48 AM

Last night, as is my normal practice after putting my scope to sleep, I grabbed a pair of binoculars for a quick look around. I happened to choose the Nikon 10x50 Actions, I do like the wide field.

I was looking at the 3 stars in Orion's belt and was quite surprised to see how much the stars dimmed if I moved the field so one of the bright stars would near the edge. As it neared the edge of the field, it was like turning out the lights, probably the last 10 degrees the vignetting was very bothersome. WOW, this is not good...

Humm I said to myself, I wonder if my other binoculars are this bad. First up were my Eagle Optics Ranger Platinum 10x42s, these are 6 degree AFOV binos, there is visible vignetting right at the very edge but nothing more was immediately apparent when moved a bright star from the center towards the edge... Next up were a pair of Celestron Regal 10x50's, another pair of roof prism binos, these are only 5 degree AFoV versus the advertised 6.5 degree field of the actions. Again, these had vignetting right at the very the edge but anything more was not immediately apparent nor bothersome.

Darn.. looks like I may have to spring for the Nikon Action Extremes after all.

Jon

#2 hallelujah

hallelujah

    Fly Me to the Moon

  • *****
  • Posts: 5026
  • Joined: 14 Jul 2006
  • Loc: North Star over Colorado

Posted 12 February 2013 - 09:06 AM

NIKON 10X50 ACTION EXTREME :(

#3 ronharper

ronharper

    Vanguard

  • *****
  • Posts: 2205
  • Joined: 14 Feb 2006

Posted 12 February 2013 - 10:32 AM

Jon,
An easy and objective, although not quantitative, indication of vignetting is to hold the binocular out at arm's length towards a brightly lit scene, and watch the exit pupil as you tilt the binocular and approach the edge of the field. The degree to which it is cut off into a football shape is what you are looking for. As long as even half the original area is preserved, the effect will not be too noticeable.

In the daytime when the eye pupils are small, they can impose an additional cutoff mechanism which the test of course won't reveal. That component will be complicated further by inconsistencies in eye positioning. But at night, when the eye pupils are wide, the test above tells most of the story.

It's not so much a quality issue as a deliberate design compromise--do you really want to pay for and carry around the honking prisms, etc, that an unvignetted system would demand? For example, Leicas, although of very high build quality, are quite bad in this way.

Why worry about the edge of field in an Action? It's not worth much anyway is it?
Ron

#4 RichD

RichD

    Surveyor 1

  • -----
  • Posts: 1964
  • Joined: 08 Nov 2007
  • Loc: Derbyshire, UK

Posted 12 February 2013 - 10:54 AM

http://www.eagleopti...50-fmt-sx-bi...

No vignetting in these!

#5 Mark9473

Mark9473

    Cosmos

  • *****
  • Posts: 8554
  • Joined: 21 Jul 2005
  • Loc: 51°N 4°E

Posted 12 February 2013 - 10:58 AM

Did you mean hold them and look in from the front, Ron?

#6 ronharper

ronharper

    Vanguard

  • *****
  • Posts: 2205
  • Joined: 14 Feb 2006

Posted 12 February 2013 - 11:42 AM

Mark,
I look into the eyepieces and watch the shape of the exit pupils. I am confident that is relevant, since it is an exit pupil effect that is seen as vignetting.

But looking in through he front might tell the same thing. Hmm, would it tell you exactly the same thing? I can't make up my mind on this one, not having a binocular handy to try it.
Ron

#7 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 43429
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 12 February 2013 - 11:44 AM

Why worry about the edge of field in an Action? It'snot worth much anyway is it? Ron


It's not so much a worry as an awareness. And too, that vignetted edge Is the difference between the 5 degree AFoV of the Regals and the 6 plus degree AFoV of the actions. I have new respect for the Regals.

Jon

#8 Rich V.

Rich V.

    Skylab

  • *****
  • Posts: 4018
  • Joined: 02 Jan 2005
  • Loc: Lake Tahoe area, Nevada, USA

Posted 12 February 2013 - 11:48 AM

It works from either end; take your pick. You have to move further off axis when looking at the exit pupil from the eyepiece end, though.

Rich

#9 ronharper

ronharper

    Vanguard

  • *****
  • Posts: 2205
  • Joined: 14 Feb 2006

Posted 12 February 2013 - 12:02 PM

Rich,
You helpless 10x50 Fujinon fan you!

Do the test I described, and if the exit pupil is still circular when it encounters the edge of the field, I'll.....um......I'll set my 10x56 FL slightly out of focus(yeah, in the center) and try to split close doubles for an hour. If I'm right, you must go birding with that IF monster.
Ron

#10 GlennLeDrew

GlennLeDrew

    Voyager 1

  • *****
  • Posts: 10508
  • Joined: 17 Jun 2008
  • Loc: Ottawa, Ontario, Canada

Posted 12 February 2013 - 02:02 PM

The test Ron described is rather more reliable when examining the exit pupil; looking through the objective shows an eyepiece-produced image which utilizes *all* visible, unmasked eyepiece glass, including portions not contributing to image-forming light in the smaller exit pupil beam corresponding to the field angle defined by one's sight line.

The nearly arm's length examination of the exit pupil's areal change while swinging the bino through the full range of apparent field angle is a pretty good indicator of the variation in field illumination.

Of course, if the observer's pupils are smaller than the exit pupil, binocular is stopped down and the light fall-off gradient is reduced. If the eye's pupil is smaller than the minimal minor axis of the truncated exit pupil, the illumination fall-off is near zero. It's not expected to be truly zero, because of the normal change in transmission of light as it traverses the optical elements at angles varying with field angle.

If one wanted a very good measurement of illumination fall-off, a light meter which could sample the full exit pupil from some fixed distance while swing through the requisite angle would integrate both the area and the transmission efficiency. The result would be the fall-off with field angle corresponding the worst case scenario, where the eye's pupil is at least as large as the exit pupil.

This brings up an additional point, regarding low-index prisms. Take for example a Porro bino using BK-7 prisms, and the familiar 'diamond' of blue-grey darkening in the outer exit pupil. As one swings the bino while examining the exit pupil, the 'diamond' shifts laterally across the exit pupil, becoming notably offset when the semi-angle of the AFoV is approached. This us due to the relevant prism surfaces *not* lying at the objective, but rather somewhere between the objective and eyepiece, and at different distances to boot. This puts each of the four blue-grey 'cut-offs' at a slightly different distance behind the exit pupil firmed by the more distant objective.

Complicating things even further... If the bino works at full aperture at least on axis, once the entrance pupil of the objective becomes clipped by the frontmost prism aperture at some off-axis angle, that edge of the exit pupil, being formed by the nearer-to-focus prism aperture, lies a small distance in space behind the rest of the image of the objective's edge.

In short, the closer to the focus lies any contributor to the exit pupil, the farther behind the image of the objective it lies. This can be seen by examining the exit pupil with a 7-10X loupe, or an eyepiece of about 20-25mm focal length (reversed, if necessary). One will see that by moving the loupe along the optical axis various bits inside can be brought into focus over a range of distance. And don't forget to do this over a range of field angles; most instructive!

This effect is more pronounced when the ratio of objective-to-focus distance relative to prism system-to-focus distance is large, and when the eyepiece focal length is long.

#11 RichD

RichD

    Surveyor 1

  • -----
  • Posts: 1964
  • Joined: 08 Nov 2007
  • Loc: Derbyshire, UK

Posted 12 February 2013 - 04:16 PM

deal Ron! I like birding with the FMT anyway, masochist that I am.

#12 Mr. Bill

Mr. Bill

    Fly Me to the Moon

  • *****
  • Posts: 6106
  • Joined: 09 Feb 2005
  • Loc: Northeastern Cal

Posted 12 February 2013 - 05:05 PM

deal Ron! I like birding with the FMT anyway, masochist that I am.


As many (LOTS) of optical "toys" as I have bought/sold over the years, my Fuji 10x50s are keepers (in spite of the "fingernails" in the exit pupil.)

Hard to find anything to match the build quality/price.

Also, the Fuji 16x70s are keepers. I sold my first pair, regreted it, bought another pair.

:cool:

#13 hallelujah

hallelujah

    Fly Me to the Moon

  • *****
  • Posts: 5026
  • Joined: 14 Jul 2006
  • Loc: North Star over Colorado

Posted 12 February 2013 - 07:57 PM

deal Ron! I like birding with the FMT anyway, masochist that I am.


Rich,

How's the depth of focus, on the Fujinon 10x50, when it comes to birding? (under 100m) :question:

Stan

#14 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 43429
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 12 February 2013 - 08:06 PM

deal Ron! I like birding with the FMT anyway, masochist that I am.


Rich,

How's the depth of focus, on the Fujinon 10x50, when it comes to birding? (under 100m) :question:

Stan


Stan:

My 10 x 50 Regals do not have the individual focusers that are almost a necessity for birding and their close focus is limited, only about 8 feet.

Should I be considering the Fuginon 10 x 50s...

:foreheadslap: :whee: :foreheadslap:

Jon

#15 hallelujah

hallelujah

    Fly Me to the Moon

  • *****
  • Posts: 5026
  • Joined: 14 Jul 2006
  • Loc: North Star over Colorado

Posted 12 February 2013 - 08:30 PM

Since we are wandering off-topic perhaps we need to start a new thread.

Or would you prefer a PM. :question:

Stan

p.s. I sent a PM

#16 RichD

RichD

    Surveyor 1

  • -----
  • Posts: 1964
  • Joined: 08 Nov 2007
  • Loc: Derbyshire, UK

Posted 13 February 2013 - 06:13 AM

depth of focus on the 10x50 FMT is reasonable Stan. Forget the thing for close focus birding obviously, but I had great fun watching buzzards and eagles in Scotland a while back with them.

#17 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 43429
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 13 February 2013 - 07:13 AM

depth of focus on the 10x50 FMT is reasonable Stan. Forget the thing for close focus birding obviously, but I had great fun watching buzzards and eagles in Scotland a while back with them.


According to the Eagle Optics website, the close focus on the 10 x 50 FMTs-SX's is 35 feet, there's a lot of birding to be done at distances closer to 35 feet.

But... I have to add another WOW and HUMM to this thread. Last night I spent about 3 hours at an Elementary School star party. Conditions were perfect, not a cloud in the sky, seeing rock solid.. Lots of people. Long Lines at my two scopes.. I must say I was amazed at how few people knew the Pleiades or even seemed to have heard the name before.

Anyway, when I got home, I had to unload everything and when I was done, I spent about 10 minutes with the 10 x 50 Nikon Actions. This time, I did not see the serious vignetting I had seen the night before. I tried the same tests, I tried to mess with the inter-ocular separation, the eye cups, I could not duplicate what I had previously seen. There was minor vignetting but it was acceptable and I could pick M93 out of the light pollution essentially all the way to the edge.

I can only figure that the first night, somehow I was not seeing the entire field of view with both eyes so when I reached a certain point, I was only viewing with one eye and the image dimmed.

Jon

#18 RichD

RichD

    Surveyor 1

  • -----
  • Posts: 1964
  • Joined: 08 Nov 2007
  • Loc: Derbyshire, UK

Posted 13 February 2013 - 07:35 AM

I must admit after reading your first post Jon, that I had never seen such noticeable vignetting in any binocular before, going by your description. I have looked, and I have owned some "budget" models in the past believe me.

#19 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 43429
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 13 February 2013 - 10:25 AM

I must admit after reading your first post Jon, that I had never seen such noticeable vignetting in any binocular before, going by your description. I have looked, and I have owned some "budget" models in the past believe me.


I definitely saw it but it had to have been something I was doing...

Jon

#20 RichD

RichD

    Surveyor 1

  • -----
  • Posts: 1964
  • Joined: 08 Nov 2007
  • Loc: Derbyshire, UK

Posted 13 February 2013 - 10:45 AM

Just the right angle maybe? Vignetting will certainly be there in almost all binoculars, but I never notice it, even when looking for it. Maybe you have more sensitive eyes.

#21 hallelujah

hallelujah

    Fly Me to the Moon

  • *****
  • Posts: 5026
  • Joined: 14 Jul 2006
  • Loc: North Star over Colorado

Posted 13 February 2013 - 01:17 PM

depth of focus on the 10x50 FMT is reasonable Stan.
Forget the thing for close focus birding obviously....


Rich,

I was curious because my Fujinon 7x50 FMTR-SX has alot of depth, and I can even, reasonably, close focus with it, in my backyard.

Thanks,

Stan

#22 hallelujah

hallelujah

    Fly Me to the Moon

  • *****
  • Posts: 5026
  • Joined: 14 Jul 2006
  • Loc: North Star over Colorado

Posted 13 February 2013 - 01:20 PM


I definitely saw it but it had to have been something I was doing...

Jon


Jon,
Next time be sure and remove the right lens cap. :tonofbricks:

Stan

#23 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 43429
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 13 February 2013 - 03:21 PM



I definitely saw it but it had to have been something I was doing...

Jon


Jon,
Next time be sure and remove the right lens cap. :tonofbricks:

Stan


:rofl2::rofl5:

Stan:

Been there, done that. It was probably something about as stupid.. tree in the way or something...

Jon

#24 EdZ

EdZ

    Professor EdZ

  • *****
  • Posts: 18820
  • Joined: 15 Feb 2002
  • Loc: Cumberland, R I , USA42N71.4W

Posted 13 February 2013 - 04:33 PM

--do you really want to pay for and carry around the honking prisms, etc, that an unvignetted system would demand? For example, Leicas, although of very high build quality, are quite bad in this way.

Why worry about the edge of field in an Action? It's not worth much anyway is it?
Ron


When you look thru a binocular your perception of the image brightness is not only influenced by what happens directly in the center of view, but also by what happens across the entire view. This article explains why less vignette may be far more important than you might think

http://www.cloudynig...hp?item_id=2407


edz

#25 EdZ

EdZ

    Professor EdZ

  • *****
  • Posts: 18820
  • Joined: 15 Feb 2002
  • Loc: Cumberland, R I , USA42N71.4W

Posted 13 February 2013 - 04:41 PM

depth of focus on the 10x50 FMT is reasonable Stan. Forget the thing for close focus birding obviously, but I had great fun watching buzzards and eagles in Scotland a while back with them.


According to the Eagle Optics website, the close focus on the 10 x 50 FMTs-SX's is 35 feet, there's a lot of birding to be done at distances closer to 35 feet.

But... I have to add another WOW and HUMM to this thread. Last night I spent about 3 hours at an Elementary School star party. Conditions were perfect, not a cloud in the sky, seeing rock solid.. Lots of people. Long Lines at my two scopes.. I must say I was amazed at how few people knew the Pleiades or even seemed to have heard the name before.

Anyway, when I got home, I had to unload everything and when I was done, I spent about 10 minutes with the 10 x 50 Nikon Actions. This time, I did not see the serious vignetting I had seen the night before. I tried the same tests, I tried to mess with the inter-ocular separation, the eye cups, I could not duplicate what I had previously seen. There was minor vignetting but it was acceptable and I could pick M93 out of the light pollution essentially all the way to the edge.

I can only figure that the first night, somehow I was not seeing the entire field of view with both eyes so when I reached a certain point, I was only viewing with one eye and the image dimmed.

Jon


Jon,

the Nikon Actions I tested had dramatically imbalanced vignette, far more on one side of the barrel than on the other side of that barrel. And both 8x40s and 10x50s had more vignette than the Nikon Action Extremes of same size and were more out-of-balance.

FWIW, I measured the close focus of the Fujinon FMT SX 10x50 at 50 feet.

I also measured the Regal LX RP 10x42 and 8x42 as quite good for lack of vignette, unusual for a roof prism binocular. In general roof prisms have far more vignette than porros, even less exxpensivvee (but not cheap) porros. Also both those Regals are centeer focus. I'm surprised the 10x50 is nott.






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics