Nikon 8x20 Lx Vs.10x25?? (3 Viewers)

[kabsetz]

Henry, mine hurts too, and in addition, I have imbibed a moderate amount of red wine. However:

1) I think we are still somewhat confused by Elk's earlier valiant efforts to quantify brightness using Tfov as one of the variables. As you yourself pointed out (if I remember correctly), narrowing the field of view only cuts off light entering from the periphery which the field stop now cuts away, and this light - if it would enter the retina - would only participate in forming that peripheral image. Thus, the brightness of the image which projects onto the "sweet spot" of the retina is not at all influenced by the true any more than the apparent field of view.

2) As the size of the retinal projection of a point source is the same in a 10x25 and an 8x20, but the light intensity of that same point source within that retinal projection is 1.56x greater in the 10x25. You would agree, would you not, that this applies no matter where in the viewfield the point source is located, if for convenience's sake we ignore the vignetting hobgoblin or just assume that it is identical for both binoculars under discussion. Now, we may get back to my model of a non-point source object virtually consisting of an infinite number of adjoining and overlapping point sources...

Kimmo

 

[elkcub]

... What if the TFOV of the two binoculars were the same? The eyepiece fieldstop would have to be larger in the 10X25 and as a result more total light would exit the eyepiece. However, its AFOV would be larger in the now familar 10 to 8 ratio, so the size of its retinal projection circle would be larger by the same amount, exactly compensating for the larger amount of light that exited the eyepiece and keeping the surface brightness on the retina equal to the 8X20. Once again I agree with everyone that higher magnification makes things look brighter, but I don't think that phenomenon can be attributed to higher surface brightness on the retina if exit pupils are equal.

All,

Looking at some other 8x/10x binocular pairs made by the same manufacturer, it would appear that they differ slightly in the extent of tradeoff between objective size and FOV. Compared to the Swarovski's, the Zeiss pair (circa 1995), for example, has a smaller 8x FOV= 345 (assuming no catalog typos) but the same 10x FOV = 285. Hence the FOV area ratio is 1.46 rather than what it should be, i.e., 1.56. It would appear, then, that the manufacturer can and does play with the field stop variable. Based on my simple conception, therefore, I would conclude that the Zeiss 8x produces slightly less total light throughput as measured at the EP, but this would be compensated for by the smaller AFOV keeping the apparent brightness equal. Nikon Sporstars (if anyone ever heard of them) are a slightly different story. The real fields are 330 ft. and 263 ft. respectively, but the area ratio is 1.57 — slightly greater than a perfect 1.56.

My Swarovski pair cooperated by having identical AFOVs and a FOV area tradeoff that exactly compensated for the change in objective size (to the first decimal place). It is a special case, however.
-elk

 

[henry link]

Kimmo,

I posted a reply to your post #41, but then decided to delete it. I'll try to come up with something more persuasive or at least clearer.

Henry

 

[Swedpat]

What I can see the simple answers of this question can be got of following questions:

1: Does a 20x80 give a much brighter image than a 8x32?

2: Does a wide angel bino of same power and aperture give a darker image than one with small FOV?

If the answer is indisputable YES, then it's proofed that a larger aperture gives a brighter relative brightness despite the same exit pupil.

Patric

 

[Rico]

Strange thread to find a treatise on brightness. |=)| I thought the thought experiment of #27 quite illuminating. But seriously, the concept of perceived brightness could do with a formal definition to make the conversation useful: perhaps a definition based on retinal images. By what measure are two such images of equal brightness? When that is known, the analysis can work backward: from iris, EP, objective, to the object itself.

 

[iporali]

1: Does a 20x80 give a much brighter image than a 8x32?

No, but the 20x80 has a much bigger "twilight factor" - an over-simplified value which describes that both magnification and aperture help in seeing faint stars.

2: Does a wide angel bino of same power and aperture give a darker image than one with small FOV?

No - imagine a slide projector which projects the slide (intermediary image in binoculars) on a screen. Now, imagine the same slide mounted in frames with larger or smaller hole/aperture (corresponding the fieldstops in a binocular eyepiece): the "narrow angled" slide projection is no brighter than a "wide-angled" - just narrower.

Ilkka

 

[Swedpat]

Thank you Ilkka for your explanation!

I understand that a higher twilight factor helps seeing fainter stars, but doesn't always help to discover darker details in, for example, a dark forest. If an object during a such circumstance is too dark to notice with a 8x32, it will not help to use a 20x80 (Magnified darkness = darkness). The only solution in that case is to increase the relative brightness, either by decrease magnification or increase the aperture.

Patric

 

[iporali]

Patric,

Actually I tried to avoid saying that . Magnification does help also in seeing details in dark forests, but that is because of the eyes (and brains and whatever), not because of increased brightness. If I remember correctly, Henry Link showed with his pair of zoom binoculars that by increasing magnification the ability to see details improves although the exit pupil becomes smaller.

Best regards,

Ilkka

 

[Swedpat]

Ilkka,

I also have discovered the fact that an increased power helps seeing details despite the image becomes significantly darker, but I think you agree with me that this works to a such limit. In "total" darkness a larger image scale will not help, and in that case it needs an increased exit pupil, either by increasing aperture or decreasing magnification. That means the twilight factor can't be used without taking any consideration to the brightness. In a case when a 12x50 will give completely dark image a 7x50 can bring out details. Or a very good example is a zoom spottingscope: a 20-60x60 scope has the highest twilight factor at the highest power despite it in reality has the best twilight performance around the lowest power. 1mm exit pupil isn't suitable in any twilight condition, and there the 3mm exit pupil at the lowest power will work better.

Regards, Patric

 

[elkcub]

Ilkka,

I also have discovered the fact that an increased power helps seeing details despite the image becomes significantly darker, but I think you agree with me that this works to a such limit. In "total" darkness a larger image scale will not help, and in that case it needs an increased exit pupil, either by increasing aperture or decreasing magnification. That means the twilight factor can't be used without taking any consideration to the brightness. In a case when a 12x50 will give completely dark image a 7x50 can bring out details. Or a very good example is a zoom spottingscope: a 20-60x60 scope has the highest twilight factor at the highest power despite it in reality has the best twilight performance around the lowest power. 1mm exit pupil isn't suitable in any twilight condition, and there the 3mm exit pupil at the lowest power will work better.

Regards, Patric

Patric,

Increasing magnification from binoculars A to B aids in seeing details, primarily because more retinal sensors (rods and cones) can be used to process the subject of interest. This is why you move closer to the written page in poor light — to increase image size. The increase in retinal sensors is an area function and proportional to the square of the respective magnifications, i.e., (Power B/Power A)^2.

The "twilight factor" T = (Power x Objective)^.5. Hence, T will increase with either an increase in power or objective size. An increase in power greatly increases the available sensors, which explains why Henry Link observed greater acuity at high magnification with a zoom, where the objective size is fixed. An increase in objective size, with power constant, increases the amount of light sent to the retina, which is also an area function. So the two variables work in concert to help visual acuity.*

Relating this to the discussion in earlier posts, note that binoculars with a fixed exit pupil can differ markedly in twilight performance. EP = Objectve/Power. So, an 8x20 and 10x25 both have the same EP = 2.5, but the T values are 12.6 vs 15.8 respectively. Hence, other factors being equal the 10x25 is better to use for twilight visibility, even though the open-field physical transmission (brightness) is the same.**

Regards,
Elkcub
PS. Much of this is the same as what Ilkka said in post #46.
* We need to be careful to distinguish light vs. dark adaptation conditions, also known as photopic vs. scotopic vision. The eye works quite differently in each condition.
** Apparent "brightness" is a complex and deceptive issue. It is thought to be primarily a subjective response to the amount of light per unit area projected onto the retina, but in the end it has a lot to do with the stimulus conditions and manner in which it is evaluated.

 

[henry link]

I agree with Ikka and Elkcub's last few posts today, and I can confirm that my experiment with a pair of 8-16X40 zoom binoculars in low light tended to validate the "twilight factor" notion that higher magnification allows the eye to see more detail in low light even though the image gets darker. I think if you try it, Patric, that you will find that more small detail is visible in dark higher magnification images than in brighter low magnification from the same instrument.

I'm off to the NC mountains for a few days of birding. I expect to find everything on this thread completely sorted out to everyone's satisfaction by the time I get back. ;-))

Henry

 

[Swedpat]

I think if you try it, Patric, that you will find that more small detail is visible in dark higher magnification images than in brighter low magnification from the same instrument.
Henry

Yes, Henry. I don't object against that. It's also my experience. What I mean is that the twilight factor is dependence of adequate brightness to have any value. If the situation is that the image of a 8x20 is totally dark and it's impossible to see any detail undependence of distance from the object (light sources is another thing), you will not see any detail using a 10x25 (or 20x50) either, because magnified darkness = darkness. (You will not be more able to read the text in a book in a totally dark room by holding the book nearer your face) But maybe a 5x25 or a 10x50 succeed.
Therefore I have hard to accept that it's a correct statement that a 10x25 is better than a 8x20 for TWILIGHT, it's better in ANY circumstance in which you will be able to define anything.

But then I want to say that MY PERSONAL definition of twilight performance is not only ability to discover details in lowlight areas, but also to experience the enjoyment of a clear and bright image at dawn and dusk. Therefore I have a passion for large exit pupils, even if they in many cases don't give the best result if you want to discover details.

Thanks for an interesting discussion!

Regards, Patric

 

[elkcub]

... I'm off to the NC mountains for a few days of birding. I expect to find everything on this thread completely sorted out to everyone's satisfaction by the time I get back. ;-))

Henry

Henry,

Enjoy your birding Henry. We'll try to be good. :t:

-elk

 

[elkcub]

Yes, Henry. I don't object against that. It's also my experience. What I mean is that the twilight factor is dependence of adequate brightness to have any value. If the situation is that the image of a 8x20 is totally dark and it's impossible to see any detail undependence of distance from the object (light sources is another thing), you will not see any detail using a 10x25 (or 20x50) either, because magnified darkness = darkness. (You will not be more able to read the text in a book in a totally dark room by holding the book nearer your face) But maybe a 5x25 or a 10x50 succeed.
Therefore I have hard to accept that it's a correct statement that a 10x25 is better than a 8x20 for TWILIGHT, it's better in ANY circumstance in which you will be able to define anything.

But then I want to say that MY PERSONAL definition of twilight performance is not only ability to discover details in lowlight areas, but also to experience the enjoyment of a clear and bright image at dawn and dusk. Therefore I have a passion for large exit pupils, even if they in many cases don't give the best result if you want to discover details.

Thanks for an interesting discussion!

Regards, Patric

Patric,

I think everyone would agree that with no light at all vision is futile. However, during the day we have sunlight and at night we have moonlight or starlight, so there is never really a complete absense of light. During the day the retina is physiologically adapted to sunlight and primarily uses cone receptors in the foveal (central) region to process color details (photonic vision). At night the retina becomes dark adapted, a process that involves physiological changes to the rod sensors that lie outside the central fovea (scotopic vision). The latter takes 30 min. or so to accomplish during which night vision becomes optimized. During this adaptation period vision is very unpredictable. There is a third region called "mesotopic vision" that lies between the two extremes, which is partly daylight and partly night vision. This region is demarcated by luminances roughly between 10^2 and 10^-2 abs, and is probably the most difficult to study or understand.

In this framework it seems to me that your definition of "twilight," dawn, and dusk, is primarily the hi mesotopic, low photopic region were some color is visible, and rod cells may be partially dark adapted. The strategy of having a large exit pupil makes sense so that more available light can be draw into the eye to stimulate these partially dark-adapted rod cells. Beyond that it's every birder stumbling around for his/her self.

Regards,
Elkcub

 

[steve johnson]

This has been a great thread! I have played with this question for several years and this set me off doing a few more observations. I tried a 10x42, an 8x32, a 6x24, and a 3x12 monocular. All appeared to give the same brightness when a dim uniform field was observed. With bright sources the higher power was no brighter if the distance was changed to make the true field the same for all instruments. I also found no difference in ability to read small type when distance was compensated for in proportion to the magnification. I even tried an 5x10 for the issue of detail and did not really see any, although it is not as bright of course. The detail test was again more or less the same for all instruments, with the exception that the newer Leica's might have been a bit better than those that were 40 years old. If there is some threshold at which the lens size is too small - I can not find it with these simple tests.

 

[NDhunter]

Greetings!

I have compared both Nikon HG 8x20 and HG 10x25 models extensively, as well as the Zeiss and Leica (Trinovid and Ultravid) equivalent models. Here's my 0.02:

For compact optics, the 10x25 is superior to 8x20 in almost every way. Brighter, sharper, and better performing in low light conditions, and exhibiting superior sharpness over distance. The only disadvantages to the 10x25's are the usual ones associated with high magnification (restricted FOV, less depth of field, shakiness, etc.).

I'm an unabashed and outspoken fan of low-power optics, 7x being my favorite all around. However, for compact optics, the 8x20 models just don't quite have adequate aperature width to perform as well as the 10x25 models - in my opinion 8x25 would be a MUCH better design for binocular companies to adopt. I think this is a case of ergonomics outweighing optical performance, where the designers decided to reduce the aperature to obtain the same exit pupil size and obtain smaller size/weight as a result - not realizing how much sharpness-over-distance and low light performance would be sacrificed in the process.

I own both Zeiss Victory 8x20's as well as Nikon HG 10x25's, and until the Ultravid compacts appeared I considered both of them to be the best binoculars in their class. Currently, I would rate the Ultravid and Nikon 10x25 models as equals optically, and the Ultravid 8x20 as slightly superior to the Zeiss Victory 8x20. If you choose 10x25 (which I HIGHLY recommend you do!) then it comes down to a question of ergonomics, whether you like the "feel" of the Ultravid or the Nikon better. I personally like the new Ultravid ergonomics very much, but they don't give me the "confidence" regarding their ruggedness that the Nikon does. I will probably end up purchasing a set of 10x25 Ultravids in the future, but for now I'm very happy with my Nikon HG 10x25's and even if I do purchase Ultravids I won't be selling the Nikons - I like them that much.

For me personally, it seems that the ONLY valid reason for choosing an 8x20 over a 10x25 would be the size and weight issues, but there is really so little difference between the two configurations that you should think long and hard before making your decision based solely on this factor.

Best wishes,
Bawko

P.S. Just a side note: the Nikon HG 10x25 is, without question, the best binoculars in terms of edge-to-edge sharpness that I have EVER looked through - regardless of configuration, aperature size, brand, or cost.

Dredging up and old thread from the past, but I do want to bring this one up.

I have recently acquired a Nikon 10x25 LXL, as I wanted a pocket type for travel, and easy carry. I have had a 8x20 Leica Trin. and a Zeiss 8x20 Victory in
the past so have had some experience with the pockets, but did not find them
quite to my liking.
This old thread awoke my interest in the 10x25, so I wanted to try one. I do think the 25mm objective does help a lot in the pockets, just take a look at the
recent thread for the Zen-Ray wish list.
The only thing I had close to compare these with was my 8x25 Nikon Travellite,
and I found the 10x25, easily beats this one in resolution and brightness, no surprise, as these are both in different classes. But, I thought the reverse
porro would be better in brightness but was not. I was really impressed by the
edge to edge sharpness of the LXL as it is as good as anything Nikon.:t: The
10x25 has a FOV of 5.4, and it is a great view by any standards.
These have the double hinge, and they can be fiddly, but I found if they are
tightened up properly, once set, they offer a nice view. The IPD setting is
very important when using these small pockets, and I found the previous advice
of using the forehead brace with the forefingers and focusing with the pinky really helps.

For some users of the small Nikon, I did tighten the hinges, so they do not move
while hanging on the strap, but they do fold up as normal when wanting to put
in the case. If you would like to know more about that, send me a PM.

Some others here, Henry, Kimmo and Elkcub have some great posts here, and
many will find them of interest.

Jerry

 

[Dennis Mau]

Dredging up and old thread from the past, but I do want to bring this one up.

I have recently acquired a Nikon 10x25 LXL, as I wanted a pocket type for travel, and easy carry. I have had a 8x20 Leica Trin. and a Zeiss 8x20 Victory in
the past so have had some experience with the pockets, but did not find them
quite to my liking.
This old thread awoke my interest in the 10x25, so I wanted to try one. I do think the 25mm objective does help a lot in the pockets, just take a look at the
recent thread for the Zen-Ray wish list.
The only thing I had close to compare these with was my 8x25 Nikon Travellite,
and I found the 10x25, easily beats this one in resolution and brightness, no surprise, as these are both in different classes. But, I thought the reverse
porro would be better in brightness but was not. I was really impressed by the
edge to edge sharpness of the LXL as it is as good as anything Nikon.:t: The
10x25 has a FOV of 5.4, and it is a great view by any standards.
These have the double hinge, and they can be fiddly, but I found if they are
tightened up properly, once set, they offer a nice view. The IPD setting is
very important when using these small pockets, and I found the previous advice
of using the forehead brace with the forefingers and focusing with the pinky really helps.

For some users of the small Nikon, I did tighten the hinges, so they do not move
while hanging on the strap, but they do fold up as normal when wanting to put
in the case. If you would like to know more about that, send me a PM.

Some others here, Henry, Kimmo and Elkcub have some great posts here, and
many will find them of interest.

Jerry

I agree with everything positive said here about the Nikon 10x25 HGL. It is the best compact binoculars I have ever tried and WAY better than the 8x20. The only binocular I have seen which is better at the edge is the Canon 10x30 IS. You can pick them up for about $300.00 too. Good bargain.

 

[ceasar]

Neither Eagle Optics or Camera Land have the 10 x 25's in stock. They are a "Special Order" item at Camera Land.

Does this signify anything about their future? They are currently listed under Nikon's "Premium" label.

Bob

 

[Hermann]

This old thread awoke my interest in the 10x25, so I wanted to try one. I do think the 25mm objective does help a lot in the pockets, just take a look at the recent thread for the Zen-Ray wish list.
The only thing I had close to compare these with was my 8x25 Nikon Travellite, and I found the 10x25, easily beats this one in resolution and brightness, no surprise, as these are both in different classes. But, I thought the reverseporro would be better in brightness but was not. I was really impressed by the edge to edge sharpness of the LXL as it is as good as anything Nikon.:t: The 10x25 has a FOV of 5.4, and it is a great view by any standards.

I also got a Nikon 10x25 HGL a few weeks ago, and I *really* like it. It's the first compact I've used that offers a view I'd call "addictive". Really, really nice.

Interestingly, the 10x25 is often somewhat cheaper over here than the 8x20, probably because most people go for the 8x20. Those people don't know what they're missing ...

Hermann

 

[NDhunter]

Neither Eagle Optics or Camera Land have the 10 x 25's in stock. They are a "Special Order" item at Camera Land.

Does this signify anything about their future? They are currently listed under Nikon's "Premium" label.

Bob

Bob:

I got mine as a demo from Doug at Cameraland, so they are priced right,
and Nikon demos seem to be as new from the ones I've tried.
I, also do not see many internet merchants carry them, so I do not
have much to add here. It seems many of them do not stock but will
order them for you. What you see is them listed as the Premier, which
is really the same as the 10x25 LXL, Nikon 7507.

In this compact I have found no CA, perfect edge to edge sharpness with the smallish FOV, and great resolution, no field curvature, these are
highly rated by the previous posters, and I agree.
What this tells me, is that ED glass is not really required in the design of
a quality pocket optic, as the other Alphas have not yet, and I do not see
how it can add to the view. By the way, the focuser has the smooth Nikon feel, as its larger siblings, and although at the objective end, it soon
is easy to get used to.
It is easily the best bargain in its size class. :t: Now it may not fit for most users everyday optic, but is a great one to have for its size.

Jerry