Best warbler glass available? (1 Viewer)

By far the most important factor controlling DOF in binoculars is the magnification. A second important factor, far more important than, for instance, eyepiece construction or effective f/number of the objective, is the accommodation range of the human eye. It thus depends to a large extent on the age of the user as the accomodation range decreases with increasing age.

Taking 8x bins as an example, with the binoculars focussed to infinity: For a 30-year-old with an accommodation range of 7 diopters everything from 9.1 meters to infinity is sharp (8x8/7=9.1 meters). (Of course, in real life most people would refocus their binoculars at distances closer than, say, 30 meters or so, because it puts less strain on the eyes than continually focussing with the eyes.) For a 50-year-old with an accommodation range of 2 diopters things look rather different, for him the depth of field is a lot smaller, it's from 32 meters to infinity (8x8/2=32 meters).

This may in fact be one of the reasons why many older birders I know tend to get binoculars with lower magnifications, the other reason being that they find it more difficult to hold their binoculars steady.

Hermann

Kevin, thanks for the explanation. this is cool. thanks

Interesting point, Herman.

I wonder if that leads to so many conflicting view on the DOF.

It changes the perception of the DOF but the physical DOF is still the same but the young observer can move that DOF around in the view i.e. a young observer can make the whole field look "in focus" but the portion he is fixated on will be in focus. For example the young observer should be able to bring the branches in front of and behind the bird into focus. And this is why fixed focus (and semi-fixed like independent focus) bins work well for younger users.

BTW, for those that want to estimate their accommodation range try this:

1. Wear eyeglasses to correct your distance vision (bifiocal wearers don't use the reading segment for this test)
2. Determine the distance you can clearly see an object close to you (bring it up to your eyes and measure the distance fromit to your eyes)
3. Your accommodation is about 1/D diopters for D in meters (or 39/D in inches)

For example, I'm 47 year old myope (short-sighted) who needs reading glasses (+1.5D add) have an accommodation of about 1.9 diopters. Not great. I won't be changing my depth of field too much.

However all that said I do have a collection of bins with the same magnification and the same aperture and they have different DOFs (with my same older low accommodation eyes ... that's a constant). In some cases it's difficult to determine why they have the DOFs they have e.g. the Celestron Ultima DX 8x32 porro has the worst DOF of all my 8x bins even though it has a small objective and I think quite a long focal length (i.e. a larger f/number objective) it is quite clearly worse than my 8x40ish bins. So I'm quite sure there are other optical factors in the DOF in some of these bins. BTW, this bin has quite large field curvature at the edge of field (and wide FOV 8.2 degrees) so it's not a field flattener issue!

Like stray light, DOF is not something that appears on a spec sheet and so is difficult to estimate without a hands on review.

This may in fact be one of the reasons why many older birders I know tend to get binoculars with lower magnifications, the other reason being that they find it more difficult to hold their binoculars steady.

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I see a bird over there, Mabel, I saw it good (at 7x), looks like a song sparrow. I know you can't see it, but you still have good ears. It is that direction, can you confirm the song? Thanks. We better write it down, we will forget. Dang, I forgot my glasses.

Mabel: They are on your forehead Ed, as usual.

Alexis,

I feel the need to comment about my earlier suggestion. I had given AP the opportunity to try out the 8x32 EL that I had in my possession. On paper it sounded like a very close matchup for what he was looking for. After some extended usage though he found that he still preferred the 8x30 E II to it. I will leave it up to him to comment further.

Tero said:

I see a bird over there, Mabel, I saw it good (at 7x), looks like a song sparrow. I know you can't see it, but you still have good ears. It is that direction, can you confirm the song? Thanks. We better write it down, we will forget. Dang, I forgot my glasses.

Mabel: They are on your forehead Ed, as usual.

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I can just see you delivering this with a deadpan Finnish mumble (Kimi Raikkonen style, if you are an F1 fan).

Actually it was birdsong that brought me back to birding.

OK. Now way, way off topic ...

FrankD said:

Alexis,

I feel the need to comment about my earlier suggestion. I had given AP the opportunity to try out the 8x32 EL that I had in my possession. On paper it sounded like a very close matchup for what he was looking for. After some extended usage though he found that he still preferred the 8x30 E II to it. I will leave it up to him to comment further.

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Ha! OK. I like the EII very much, but for me it fails as a warbler glass because the eye-relief is on the minimal side for me and my eyeglasses. Also, the focus is not nearly as fast as the EL.

--AP

First off - FrankD is a class act, a pleasure to deal with, and a very valuable asset to this forum.

Also, I appreciate everyone's input to the thread. It's a very interesting read. Based on some of the recent posts, I'll add a little commentary.


The Swaro EL: It is my favorite 8x30-32 ROOF, and offers what I (still) believe is the best set of compromises of ANY 8X30-32 ROOF on the market (not including EDG). It is a very addicting view. The center is sharp. The sweet spot is wide. The stray light is well controlled.

The Nikon EII 8x30: Right up front, I do not wear eyeglasses. The short ER on no problem for me. In fact, with the eyecups extended, the fit of the pliable rubber is just about right. I can see all of the huge FOV. The FOV is immense - nothing even close in 8x! The focus is not fast. But, I find it very easy to obtain sharpness - I like it just fine - could have something to do with what appears to be an excellent DOF. Things I would like to change about EII: (a) more stiffness on bridge - I have adapted to this problem and can deal with it, but it's not desirable, (b) needs rubber armor (SE style?), (c) needs a longer eye-relief (and twist out eyecups)for eyeglass wearers. An EII/SE hybrid with the SE body, about 440' FOV, twist eyecups, ~ 15 mm ER, and a stiffer bridge would seemingly be a very "do-able" design, and I would suspect just about unbeatable. But, it apparently doesn't make business sense.

Optically speaking, the EL and the EII aren't too far apart overall. The EL is sharp in the center. The EII is even sharper. The EL has good color rendition - possibly just a tad yellow. The EII has neutral color. The EL has a good sweet spot. The EII has a noticeably better sweet spot. The EL has an easy view in terms of eyeplacement. The EII has noticeably easier view. The EII does have a wider FOV, but this is suprisingly not as noticeable. I will not comment on handling, etc - it's just a personal thing.

Despite the optical superiorities of the EII, I expected the EL to pull ahead in the field. It didn't. The EL was very good; but the EII was again just better. I carried both out into warbler infested habitat on a nice morning. The EL took more work to OBTAIN and MAINTAIN good views. It was mostly eye placement and sweet spot related. The EL was (in direct comparison to the EII) a bit tiring. I fidelled with the IPD; I fidelled with the eyecup extension, etc, etc. Every time I got it about as good as I could, I would pull up the EII and just relax. I finally just gave up and finished birding with the EII.

All that to say: I wonder really if the EII has an equal in terms of criteria 1,2,and 3. It now seems to me that IF it does, it will come in the form of a full sized glass.

APS

Hello,

About three years ago, I wrote:

I would have to write that the E2's larger field is very attractive and
makes
this glass very comfortable and easy to use.

I preferred the EII to the SE, for the same reasons others gave, but I did find that neither Nikons handled reflections off the eyepieces as well Leica or Zeiss binoculars. This is troublesome at early morning and for eyeglass wearers, especially, as eye cups are made to eliminate problems for strong side lighting. However I found that a low sun behind the viewer was troublesome.

In this autumnal season of warblers, I used a Zeiss 7x42 classic and a 10x32.

Happy observing,
Arthur :brains:

Kevin Purcell said:

It changes the perception of the DOF but the physical DOF is still the same but the young observer can move that DOF around in the view i.e. a young observer can make the whole field look "in focus" but the portion he is fixated on will be in focus. For example the young observer should be able to bring the branches in front of and behind the bird into focus. And this is why fixed focus (and semi-fixed like independent focus) bins work well for younger users.

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Makes a lot of sense. There's one other aspect I forgot to mention though: When focussing with your eyes from infinity to your near point, the eye pupils are drawn slightly closer together. This in turn mean that focussing with your eyes works best with binoculars with largish exit pupils. That's one of the reasons why many people find small binoculars (8x20's for instance) difficult to deal with.

But even with larger binoculars some eyepieces work better than others because some eyepieces don't work that well when you don't place the eye pupil right in the centre of the exit pupil of the eyepiece. IMO one of the reasons why the Zeiss 7x72 Classic was such a great success was that it worked very well in that respect for most people. In fact, before phase coating was introduced it was possible to avoid the detrimental effects of the roof prism by placing the eye pupil in one half of the exit pupil of the binoculars. That also worked quite well with the 7x42's, even though the binoculars were not optimized for that kind of use.

Another point: Porros may appear to some people to have a larger DOF because the image doesn't look so "flat" because of the greater distance between the objective lenses. That's largely subjective though. I personally tend to prefer porros for that reason, some of my friends on the other hand don't see any difference at all.

To come back to the original question: I personally feel that binoculars with an exit pupil of at least 4mm and a magnification of 7x to 8x work best as a warbler glass. In some habitats 10x might also work. I also think that the weight shouldn't be above something like 800 gr and the focussing should be reasonably fast. That's why I prefer my old Leica 8x32's over the Nikon 8x32 SE's, even though the optics of the SE's are better. The focussing is faster, and speed matters a lot when you're at a migration hotspot.

What's most important is that you actually try different pairs in the field to find out which one suits you best, in other words which you feel most comfortable with. I never got to grips with the Swarovski EL's, for instance. I just didn't like them. I also still prefer the "old" Zeiss Victory II over the Victory FL. Go figure.

Hermann

Hermann said:

When focussing with your eyes from infinity to your near point, the eye pupils are drawn slightly closer together. This in turn mean that focussing with your eyes works best with binoculars with largish exit pupils.
Hermann

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Considering this, would it also stand to reason that focusing with your eyes works best with binoculars with largish sweet spots ?

APS

APSmith said:

Considering this, would it also stand to reason that focusing with your eyes works best with binoculars with largish sweet spots ?

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Makes sense to me, although I feel that whether a sweet spot is really a sweet spot *for you* may also depend on the individual characteristics of your eyes.

Lots of variables there.

Hermann

Kevin Purcell said:

Like stray light, DOF is not something that appears on a spec sheet and so is difficult to estimate without a hands on review.

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Kevin.

Stray light can be measured in fact some manufacturers have stray light measurements. They would not publish them as they wouldn't for the total light transmission, but some results totally contradict many of the postings on bird forum. That is the difference between subjective and measureable, however under the circumstances that no published figures are available, you are correct, it has to be a hands on approach.

One of the criteria mentioned is "Sweet Spot" what is that? If we are talking about the relationship between FOV and the Zone. This can be measured.
Zone = FOV / Sq root 2.

Again, there are other considerations to bear in mind for the Zone (or is this the so called sweet spot) optics design for one. But it is measureable

mak

NWBirder said:

What determines the binoculars' depth of focus?

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This thread on Cloudy Nights came to the conclusion that "the only optical parameter which determines depth of field is the magnification". If you don't want to read the whole thing, scroll down to the first post by JCB, whom I have quoted above.

Michael

mak said:

One of the criteria mentioned is "Sweet Spot" what is that?
mak

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Sweet Spot =~ZONE of critical sharpness. It is the portion of the FOV which is sufficiently focused and sharp at the same time that the center is. I suppose "what's sufficient" might vary somewhat from user to user. There do seem to be very significant differences in the ZONE between different models of the same configuration. I suspect that almost all users would more or less agree on the ranking order between different given models (unless the models incomparison were truly very closely matched concerning this criteria). However, I don't expect that everyone would agree on the actual measured size of a particular model's ZONE (due to individual eyesight variation).

I'm becoming more and more convinced that the best warbler glass is indeed the one with the largest Sweet Spot, provided that the view is not so difficult to achieve and maintain that it constitutes a significant distraction (I know - personal pref., but certainly qualify-able), and provided that the stray light is well controlled. As such, it still appears that the Nikon EII and/or SE, along with the Zeiss ClassiC 7x42 are still unmatched by today's alpha roofs (the contributions of John Traynor and Pinewood give some credence to this notion).

I don't mean to sound like Paul G., but something is wrong with the binocular market today. If we continue to praise (and purchase) these current ultra-expensive models that are not as good as the stuff from 10+ years ago, aren't we cheating ourselves out of the better viewing experiences. Isn't this effectively the same thing Ingrahim said (much more eloquently) over and over on BVD. Sure, the roofs are better than ever; but, I'm not sure we're there yet. Perhaps the EDGs will be. But, if there were an optimised porro ...

One more thought. I can't help but believe that the best binoculars it the world are individual prototypes lying around the R&D labs of the manufacturers. Surely they've tried the things that seem obvious to us (the improved SE/EII, the 7x32 EL, the modernized Zeiss 7x42 ClassiC, a new 7x35 Leica). Perhaps they just need to let the engineers have more input in the marketing so the right ones are put into production.

(Sorry for the rant.)

APS

There are other threads that differ too, Macgee.

Plus as quite a few of us have noticed we have 8x bins with different DOFs even when they have the same sized objectives

So you are saying the "Zone" is 70% of the FOV

By diameter or by area? I presume the former (so the Zone would be half the area of the FOV ... that sounds like a good definition!).

Not so much measurable as defined in this case ... unless you define it as the point at which the resolution decreases by a factor of two (or some similar amount) which would then be a useful parameter for comparing bins (especially in this case for someone wanting a 90% or 95% Zone.

All of the numbers we want should be directly available from the ray-trace simulation (given accurate numbers for AR coatings, reflectivity of the tube and the like). But like the design details they aren't made available to purchasers.

Kevin Purcell said:

There are other threads that differ too, Macgee.

Plus as quite a few of us have noticed we have 8x bins with different DOFs even when they have the same sized objectives

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That's what I observed as well.

Dof

I gave up trying to finish the CN thread. I got tired if a post is more than 3 paragraphs.

Anyway, I believe the depth of field is related to ocular lens focal length and aperture (f value measured by ocular focal length divided by exit pupil). That should explain the model to model variation also why 8x has better DOF than 10x. I get a feeling that a long eye relief model (related to long ocular focal length) should have a deeper DOF. I could be wrong though. Don't flame me on this.

I may be "full of sweet spot" here, but I have come to look at this sweet spot as a sort of three dimensional entity. Part of it would be width of focus in relationship to the FOV. This is what we normally refer to as the sweet spot. The other aspect of the sweet spot would be the depth of focus or depth of field. Seems that the two must be related. So the sweet spot could be envisioned as a sphere (or sort of a cylinder) across the width and height of the FOV as well as from the near to far focus distance in the DOF.