Dioptre setting on FLs and others (1 Viewer)

This could as well be posted on another forum such as Leica but probably fits best here on Zeiss because of one of the questions below to do with poor light, a Zeiss speciality what with AK prisms in many last generation and some current generation models.

It was pointed out to me in various messages that it is best to set dioptre over a range such as 50-100 yards. Befere being told that I was setting it at much closer range, for instance as close as 10 yards. My thinking was that close focus is more intolerant of slight error so setting it on a close target would ensure better pinpoint accuracy. Out of interest why is this flawed?

The other thing I wondered about dioptre was whether the difference between my (our?) two eyes varied depending on light levels. Since different receptors - if that is the right technical term - are at play in daylight compared with in darkness, do low light and night time viewing affect the dioptre setting?

Thank you,

Tom

Hi Tom,I try to answer.

SeldomPerched said:

Out of interest why is this flawed?

Click to expand...

There is no exact answer here, for various reasons concerning the mechanical and optical functioning of the various binoculars and which also concern the individual eye.
The best situation in any case, can be found only by adjusting the diopter every time and for each focusing distance.
For each user and each specimen of binoculars it is however possible to find the best compromise and usually divide the most suitable dioptric adjustment, at least for two distances. For example, for the close distances or for the long range observations (towards infinity).
Many high quality binoculars have good-excellent tolerances in diopter adjustment, so it is not necessary to change the adjustment for near or far. But most of the binoculars for sale are not of high quality and the eye is still a very important factor in the context.
So, the best advice in my opinion is to adjust the diopter every time you need it. And after, with the using experience of that binocular, it will be easier to find the best compromise.
It should also be added that the method of checking the correct dioptric adjustment may be different for each individual and in some cases the continuous search for the correct dioptric balance could cause excessive concentration and consequent visual fatigue to avoid.
Listing the control methods could be a good point for this topic.

SeldomPerched said:

do low light and night time viewing affect the dioptre setting?

Click to expand...

In general, yes, since our eyes are never hardly perfectly symmetrical and the correct focus also changes due to the increase of the pupil (iris) in low light, but not because of the different receptors.

I think the best way to set the diopter is after focusing on a distant object with crisp edges or contrasty detail (the moon works nicely). Initial focusing, as well as diopter setting, should be done with both eyes open and entirely relaxed (i.e. with no effort made to focus using eyes' own accommodation). Using a distant object helps with eye relaxation. If desired, after finding best setting with both eyes open, use something to alternately cover left/right side (keep both eyes open) to check that left vs right focus are synchronized. I find that when I set the diopter this way, I don't need to adjust it for different distances or light levels or different days. Sometimes, one of my eyes will go wonky from (stupidly) squinting when using a scope for long periods, or because it is a windy day and one eye is more teary than the other. In those cases, fiddling w/the diopter can help a bit in the very short term, but I resist messing with it because adjusting the bin to my wonky eye only interferes with good viewing as my eye recovers, and I don't want to keep fiddling with it to try to continually tweak it during that recovery period.

--AP

Alexis Powell said:

I think the best way to set the diopter is after focusing on a distant object with crisp edges or contrasty detail (the moon works nicely).

Click to expand...

at night I use stars that are on average faint-tenuous and therefore more punctiform (to observe infinitely), while during the day I look for the reflection of the sun on a very convex surface, at the distance I need, such as drops of water or chromed bumpers of cars , motorbike, bicycle, or anything that reflects the sun in a pinpoint way. Typically, many light reflections exhibit high contrasts.

Alexis Powell said:

should be done with both eyes open

Click to expand...

Also in my opinion it is preferable to keep your eyes open. I often use to converge them slightly, so as to divide the two images and evaluate the correct dioptric balance by setting the alternating dominance of the two eyes.
I don't know if it is an easy procedure for everyone, but in normal it should be feasible with the right experience.

Alexis Powell said:

Sometimes, one of my eyes will go wonky from (stupidly) squinting when using a scope for long periods, or because it is a windy day and one eye is more teary than the other. In those cases, fiddling w/the diopter can help a bit in the very short term, but I resist messing with it because adjusting the bin to my wonky eye only interferes with good viewing as my eye recovers, and I don't want to keep fiddling with it to try to continually tweak it during that recovery period.

Click to expand...

It happens to me too, and as I think, to many.

Alexis and Rico,

Thanks for your detailed explanations. I see myself in some of the scenarii you mention! Both eyes open is certainly what I do but the moon was not something I'd not thought of so will try that.

It's probably something to do with ageing eyes (64 recently - years not eyes; I'm not Argus!) but certain brands I find much easier to zero than others. Swarovski easiest by a country mile. No idea why; could it just be that they are super-accurately aligned in the factory? On the other hand though I love Leica colours I'm not responding nearly so well to the 7x42 UVHD+ and have had it checked for correct collimation, which it passed - and have built a bit of a mental block perhaps over resolution of fine details with this glass which I believe is known for being one of their best. Nikon EDG and my big Zeiss 8x56 T*FL I quickly set on the day each arrived and have never needed to alter that initial setting since.

It would be a help if the makers could set up the dioptre scale to show the true setting. For me it seems to be around -1 dioptre (thanks, Swarovski) but another brand's offering shows +2 when correctly adjusted. How can they get away with it? Imagine a car with a speedometer that read 70 at 90 or a petrol gauge that showed quarter full when the tank was nearly dry.

Tom

Alexis Powell said:

Using a distant object helps with eye relaxation.

Click to expand...

Alexis,

Your'e not looking at a distant object. Your'e looking at the image of a distant object and this image is just a few millimetres in front of the eyepiece.
Regardless of the object distance, the viewer will focus so that its image is always in the same position.

For the normally sighted user this image would be at the focal plane of the eyepiece and the rays emanating from the eyepiece would be parallel. For the short-sighted they would diverge and for the far-sighted they would converge.

It doesn't matter how far distant the focussed object is. Just put an objective cover on the right objective and focus. Then put the objective cover on the left objective and set the diopter.

John

SeldomPerched said:

...certain brands I find much easier to zero than others...could it just be that they are super-accurately aligned in the factory?

Click to expand...

Yes, it could be. Basically I would try to replace the 7x42 UV specimen with another specimen, to find what I am looking for. Another specimen could also do much better for me. Otherwise, I would do exclude that model from my staff.

SeldomPerched said:

It would be a help if the makers could set up the dioptre scale to show the true setting...

Click to expand...

I do not believe. What is needed, is the sensitivity and ability to easily find the necessary dioptric value, regardless of absolute zero.
When the mechanics and optics are consistent and with zero tolerances, it will certainly be more convenient to have also the dioptric indexes, but they are not as necessary as the speed and petrol indicator.

Tringa45 said:

Alexis,

Your'e not looking at a distant object. Your'e looking at the image of a distant object and this image is just a few millimetres in front of the eyepiece.
Regardless of the object distance, the viewer will focus so that its image is always in the same position.

For the normally sighted user this image would be at the focal plane of the eyepiece and the rays emanating from the eyepiece would be parallel. For the short-sighted they would diverge and for the far-sighted they would converge.

It doesn't matter how far distant the focussed object is. Just put an objective cover on the right objective and focus. Then put the objective cover on the left objective and set the diopter.

John

Click to expand...

Just to confirm,

(1). Is this definitely correct?
(2). Assuming it is correct, then previous suggestions about optimum distances for setting dioptre/diopter are irrelevant?
(3). Look at my post below: I've got it right now anyway. And I confirmed by short and longer distance settings looked right straight afterwards to make sure.

Thank you,

Tom

Rico70 said:

Yes, it could be. Basically I would try to replace the 7x42 UV specimen with another specimen, to find what I am looking for. Another specimen could also do much better for me. Otherwise, I would do exclude that model from my staff.


I do not believe. What is needed, is the sensitivity and ability to easily find the necessary dioptric value, regardless of absolute zero.
When the mechanics and optics are consistent and with zero tolerances, it will certainly be more convenient to have also the dioptric indexes, but they are not as necessary as the speed and petrol indicator.

Click to expand...

Luckily soon after posting I took the bull by the horns and took my UVHD+ with me away for a few days. I have been using it exclusively and maybe because I wasn't under any time pressure was very relaxed about adjusting it and chose good conditions for when to do so. The UV is now back as it should be: a star performer to my eyes and giving a great relaxed and unstrained view. As so often, nothing wrong with the instrument -- all down to user error!

Thanks for your thoughts, Rico.

Tom

Alexis Powell said:

I think the best way to set the diopter is after focusing on a distant object with crisp edges or contrasty detail (the moon works nicely). Initial focusing, as well as diopter setting, should be done with both eyes open and entirely relaxed (i.e. with no effort made to focus using eyes' own accommodation). Using a distant object helps with eye relaxation. If desired, after finding best setting with both eyes open, use something to alternately cover left/right side (keep both eyes open) to check that left vs right focus are synchronized. I find that when I set the diopter this way, I don't need to adjust it for different distances or light levels or different days. Sometimes, one of my eyes will go wonky from (stupidly) squinting when using a scope for long periods, or because it is a windy day and one eye is more teary than the other. In those cases, fiddling w/the diopter can help a bit in the very short term, but I resist messing with it because adjusting the bin to my wonky eye only interferes with good viewing as my eye recovers, and I don't want to keep fiddling with it to try to continually tweak it during that recovery period.

--AP

Click to expand...

Great; thank you, Alexis. I have generally settled on a sheltered spot to do this, maybe with something to lean on. My procedure has been to put the objective cover over the right objective; focus as suggested with both eyes open and comfortable; pull out the dioptre cover (I think I can usually do that now without altering the focus at the same time!); reverse the procedure to use my right eye; etc etc. With some examples it's easier than others. The easiest in my opinion is when the dioptre correction is a ring on the right eyepiece. I just learn the position and reset it if it gets moved at all.

And as you can see below i finally got the UVHD+ how/where I wanted it and it's behaving just fine. Either I've broken it in or it's broken me in!

All the best,

Tom

Tringa45 said:

Alexis,

Your'e not looking at a distant object. Your'e looking at the image of a distant object and this image is just a few millimetres in front of the eyepiece.
Regardless of the object distance, the viewer will focus so that its image is always in the same position.

For the normally sighted user this image would be at the focal plane of the eyepiece and the rays emanating from the eyepiece would be parallel. For the short-sighted they would diverge and for the far-sighted they would converge.

It doesn't matter how far distant the focussed object is. Just put an objective cover on the right objective and focus. Then put the objective cover on the left objective and set the diopter.

John

Click to expand...

Additional thought, John, since my reply just now...

If this is so, what is the explanation for feeling a bit dizzy sometimes when focusing a binocular at or near to its close-up distance? For instance I can focus pretty close with an 8x32 T*FL or an EL 8.5x42 WB - and especially the latter leaves me a bit strained for 30 sec or more afterwards.

Tom

Thanks, SeldomPerched, for raising some interesting points. I'm a self confessed nitnoid when it comes to setting up my binoculars, since observing small targets over long distances is demanding, and getting all the small details just right makes a real difference over a three or four hour stint.

SeldomPerched said:

It was pointed out to me in various messages that it is best to set dioptre over a range such as 50-100 yards. Befere being told that I was setting it at much closer range, for instance as close as 10 yards. My thinking was that close focus is more intolerant of slight error so setting it on a close target would ensure better pinpoint accuracy. Out of interest why is this flawed?

Click to expand...

I agree that setting the diopter over long distances works best for me, but my typical observing distances are also quite long (500m or so Sunday morning). If I was using them over shorter distances, and I felt the diopter needed adjustment (which has not been the case), I would.

SeldomPerched said:

The other thing I wondered about dioptre was whether the difference between my (our?) two eyes varied depending on light levels. Since different receptors - if that is the right technical term - are at play in daylight compared with in darkness, do low light and night time viewing affect the dioptre setting?

Click to expand...

This, I'm fairly sure, happens to me. I do a fair amount of observation 10 to 15 minutes or so before official sunrise, and although the urban environment isn't as dark as it would be out in the country, that is definitely the trickiest time of the day. The brighter it gets the more the eye stops down and the view becomes distinctly easier, especially with smaller objective sizes like 8x30. I have to fine-tune my focus a lot more at that difficult twilight time, and although I try to avoid adjusting the diopter if possible, I have to do so on occasion. More rarely, I may need a slight diopter adjustment due to eye fatigue, but can normally avert this by opening up the IPD slightly (presumably this delivers the image into a portion of the retina that is less tired), coming off the binoculars for a short while, tweaking the focus a little, etc.

I've found that after getting the left barrel dead sharp, and then the right barrel, I often have to turn back the focus wheel a smidgen. It's as though when both eyes focus on the same object, it is a little more in focus, as it were. I normally set the diopter with my right eye shut and then the left eye, but sometimes feel that the most relaxed view can be achieved by tweaking the right barrel with both eyes open. Like you, my favourite diopter design is the traditional style, on the right-hand barrel - which I find much more user-friendly than any of the more modern integrated setups.

SeldomPerched said:

...I took the bull by the horns and took my UVHD+ with me away for a few days. I have been using it exclusively and maybe because I wasn't under any time pressure was very relaxed about adjusting it and chose good conditions for when to do so. The UV is now back as it should be: a star performer to my eyes and giving a great relaxed and unstrained view.

Click to expand...

There's nothing like relying on one binocular for a decent length of time to iron out all the little setup details (diopter, IPD, eyecups etc). I also find some binoculars I have to learn, or re-learn if not having used them for a while, how to look through them. I experience this with both my Oberkochen porros (the initial "getting to know you" phase was more difficult with the 10x50 than with any other binocular I've tried), and even the 10x40 Dialyt can takes a bit of getting used to. By contrast the view through some other models is instantly accessible. The 8.5x42 SV is amongst the best in this regard of those I've tried.

It's great you are enjoying your 7x42. There are few better things in life than a set of really good optics that have been tweaked to perfection and which you're familiar with every nuance of how they are to look through.

SeldomPerched said:

This could as well be posted on another forum such as Leica but probably fits best here on Zeiss because of one of the questions below to do with poor light, a Zeiss speciality what with AK prisms in many last generation and some current generation models.

It was pointed out to me in various messages that it is best to set dioptre over a range such as 50-100 yards. Befere being told that I was setting it at much closer range, for instance as close as 10 yards. My thinking was that close focus is more intolerant of slight error so setting it on a close target would ensure better pinpoint accuracy. Out of interest why is this flawed?

The other thing I wondered about dioptre was whether the difference between my (our?) two eyes varied depending on light levels. Since different receptors - if that is the right technical term - are at play in daylight compared with in darkness, do low light and night time viewing affect the dioptre setting?

Thank you,

Tom

Click to expand...

Tom:
You are on the right track, but it does come down to you and your eyes.

If they are good and equal between them, with a well collimated binocular
your diopter would be set close to zero.

The best way to set your diopter, is on a target with good contrast at a distance of up to 50 yds. or so. First focus with the focuser with your left
eye, then close your left eye, and just use your right and use the diopter
to make your right eye sharp. Then both should be in proper alignment
and should be clear. This is a simple lesson and the best way to do it, and many reading this can find it useful.

Once set, just leave it alone, don't play with the diopter under low light
or other, as it should not be necessary.

If your eyes are not good, then things will be more difficult.

Jerry

NDhunter said:

Tom:
You are on the right track, but it does come down to you and your eyes.

If they are good and equal between them, with a well collimated binocular
your diopter would be set close to zero.

The best way to set your diopter, is on a target with good contrast at a distance of up to 50 yds. or so. First focus with the focuser with your left
eye, then close your left eye, and just use your right and use the diopter
to make your right eye sharp. Then both should be in proper alignment
and should be clear. This is a simple lesson and the best way to do it, and many reading this can find it useful.

Once set, just leave it alone, don't play with the diopter under low light
or other, as it should not be necessary.

If your eyes are not good, then things will be more difficult.

Jerry

Click to expand...

Jerry,

Thanks - all good stuff... especially that very last paragraph! Today I had another viewing session with the same glass; left the adjustment right where I had set it & found success; and felt no need to disturb it further.

About the eyes again, though: to focus on something with easy lines, like a car, is child's play, but when it is already slightly irregular stonework, with mosses, lichens etc etched into the surface, then getting it smack on is hard. I mention this because birds come to land on top of just such a wall and it works well to know the instrument is already targeted (I only mean for observation here) to get the best view.

Tom

Patudo said:

Thanks, SeldomPerched, for raising some interesting points. I'm a self confessed nitnoid when it comes to setting up my binoculars, since observing small targets over long distances is demanding, and getting all the small details just right makes a real difference over a three or four hour stint.



I agree that setting the diopter over long distances works best for me, but my typical observing distances are also quite long (500m or so Sunday morning). If I was using them over shorter distances, and I felt the diopter needed adjustment (which has not been the case), I would.



This, I'm fairly sure, happens to me. I do a fair amount of observation 10 to 15 minutes or so before official sunrise, and although the urban environment isn't as dark as it would be out in the country, that is definitely the trickiest time of the day. The brighter it gets the more the eye stops down and the view becomes distinctly easier, especially with smaller objective sizes like 8x30. I have to fine-tune my focus a lot more at that difficult twilight time, and although I try to avoid adjusting the diopter if possible, I have to do so on occasion. More rarely, I may need a slight diopter adjustment due to eye fatigue, but can normally avert this by opening up the IPD slightly (presumably this delivers the image into a portion of the retina that is less tired), coming off the binoculars for a short while, tweaking the focus a little, etc.

I've found that after getting the left barrel dead sharp, and then the right barrel, I often have to turn back the focus wheel a smidgen. It's as though when both eyes focus on the same object, it is a little more in focus, as it were. I normally set the diopter with my right eye shut and then the left eye, but sometimes feel that the most relaxed view can be achieved by tweaking the right barrel with both eyes open. Like you, my favourite diopter design is the traditional style, on the right-hand barrel - which I find much more user-friendly than any of the more modern integrated setups.



There's nothing like relying on one binocular for a decent length of time to iron out all the little setup details (diopter, IPD, eyecups etc). I also find some binoculars I have to learn, or re-learn if not having used them for a while, how to look through them. I experience this with both my Oberkochen porros (the initial "getting to know you" phase was more difficult with the 10x50 than with any other binocular I've tried), and even the 10x40 Dialyt can takes a bit of getting used to. By contrast the view through some other models is instantly accessible. The 8.5x42 SV is amongst the best in this regard of those I've tried.

It's great you are enjoying your 7x42. There are few better things in life than a set of really good optics that have been tweaked to perfection and which you're familiar with every nuance of how they are to look through.

Click to expand...

I know about being nit-noid! Over the last few days or two as well as getting some interesting viewing in varied lighting conditions, all with that 7x42 Ultravid HD+, I have checked its focusing sharpness repeatedly against a well-weathered stone wall at about 50 yards distance, doing this at different times of day and varying cloud/sunlight dispositions. Some bright stormlighting proved to be the best for this as well as the most aesthetic. it brought out all the textures and scars in the stone and, leaving aside the stopdown effect it did allow me to be certain I had the best adjustment humanly achievable. Since then I tested in poorer light and have been able to accept the difference between best achievable and when it is too murky to be worth bothering! The great thing is that it's now possible to accept that what I am seeing is as good as it could be and very satisfying, whereas for a time before getting the dioptre right the results were just not living up to expectation from this famous glass. And whatever I look at now, from whatever distance nothing is troubling me.

Relearning is something I understand. As you say, a good idea to spend considerable time with a binocular rather than chop and change too often. Too much homework for the eyes!

"There are few better things in life than a set of really good optics that have been tweaked to perfection and which you're familiar with every nuance of how they are to look through..."

Any contender or contenders of yours for that position? I don't use it that much but the Victory 8x42 HT I bought from Troubadour is very fine and very bright (an AK design); also the 10x50 EL WB which has given me some unexpected birds - which I never managed to ID, but it is best from a position where the arms get a bit of external support, say from a window or behind a large box etc. Not to say it's unhandholdable but that way you get the best out of it.

Tom

Tringa45 said:

Alexis,

Your'e not looking at a distant object. Your'e looking at the image of a distant object and this image is just a few millimetres in front of the eyepiece.
Regardless of the object distance, the viewer will focus so that its image is always in the same position.

For the normally sighted user this image would be at the focal plane of the eyepiece and the rays emanating from the eyepiece would be parallel. For the short-sighted they would diverge and for the far-sighted they would converge.

It doesn't matter how far distant the focussed object is. Just put an objective cover on the right objective and focus. Then put the objective cover on the left objective and set the diopter.

John

Click to expand...

John,

I'll admit that my knowledge of optics is limited, and I've even forgotten at this point much of what I once learned about optical systems of basic telescopes etc, but I will defend my statement on two grounds. First, for those who accommodate slowly, keeping the eyes trained on distant objects will help keep the lenses closer to their resting (lens tensioned) state, so when bins are then brought to the eyes to test the diopter setting, the lenses will be less likely to be in a state of gradually-shifting plastic deformation. Second, it seems to me (but perhaps I am wrong--do explain) if focusing on an object at infinity, the easiest way to attain focus with normal (or corrected by glasses or contacts) vision is for the binocular to be focused at infinity and for the eyes to be focused at infinity, which is approximately their resting state. If a close-by object is used, proper focus can be achieved by doing all the focus work with the bin (as is preferred for keeping eyes relaxed) or it can be achieved by doing some of the focus with the bin and some of the near focus with eye accommodation. I find it hard in practice not to do the latter (i.e. it takes more effort to remind myself not to use my eyes). Since active focus of the eyes takes effort and that effort wavers about, it makes separately/independently setting the focus of each side of the bin to match one another difficult. For example, if one looks through the left side and uses a lot of eye accommodation while adjusting that side, then looks through the right side and leaves the eyes more relaxed while setting it, the diopter will not be set for comfortable viewing. In practice, I find that using a distant object encourages the eyes to relax.

--AP

Alexis Powell said:

In practice, I find that using a distant object encourages the eyes to relax.

Click to expand...

Hi Alexis,

yes, agree with you!

But there should still be a reason to adjust binoculars to "Infinite" for the eyes, almost all "normal" hand-held binoculars are optically optimized for "Infinity", so they show the sharpest picture.

Andreas

This is all more interesting than i thought it was going to be!
Following from Alexis' point, which i take to mean that independently setting the dioptre (one eye at a time with the other closed) forces the eye into a state that it wouldn't be in when using both (simplistic perhaps, but hopefully you'll know what i mean):
I noticed that sometimes i would do this, but then find a further minimal adjustment was necessary when in normal use. So, i started being more deliberately relaxed (eye-wise) when doing it, rather than using some form of intense concentration when dioptre-setting. This gave better and more fixed results.
So basically, i have continued to set it for the eyes independently, but to deliberately over-ride the intense attempt to focus the eye i was using previously. This was particularly true when setting the dioptre for the right eye, rather than the overall focus for the left.
I'm still using the bark of a tree at about 30m for focus point; a matter of habit, i think. Road signs, number (license) plates on cars will do when a tree isn't available.

Alexis Powell said:

First, for those who accommodate slowly, keeping the eyes trained on distant objects will help keep the lenses closer to their resting (lens tensioned) state, so when bins are then brought to the eyes to test the diopter setting, the lenses will be less likely to be in a state of gradually-shifting plastic deformation.

Click to expand...

Alexis,

I see what you mean but think the effect is minimal.
My optometrist tests for distant vision at 5 m. The difference to infinity is a mere 0,2 dioptres and he doesn't seem to consider it necessary to add 0,25 dioptres (the usual increment) to the prescription.
There are a couple of members on the forum, who get their eyes tested to 1/8th dioptre and some spectacle lens manufacturers will supply in these increments. However, for the naked or corrected human eye anything above 10 m can be considered as infinity.

There are sometimes reports on birdforum of unstable dioptre setings on binoculars. This could either be caused by a rocking bridge on a Porro bin or non-synchronous movement of the focussing lenses in a roof prism bin. AFAIK the difference in clockwise/anticlockwise torque of the focusser on some Swarovski bins is caused by spring tensioning of the focussing lenses to ensure synchronous movement.

@ Seldom Perched
Tom,

When we view a near object we squint. The optical centres of the reading lenses of my bifocals are 3 or 4 mm closer than my nominal IPD. However, the optical axes of binocular tubes are (or should be) parallel, so it's difficult to merge the images at very close distances. It does help to reduce the IPD setting a little but under 2 m it does get rather uncomfortable.

If you measure your 8,5x42 SV I think you will find that the objective spacing is a little larger than the eyepiece spacing, so in combination with the slightly higher magnification, this would exacerbate the problem. IIRC some of the old Nikon HGs had a somewhat narrower objective spacing than eyepiece spacing.

John

SeldomPerched said:

... I have checked its focusing sharpness repeatedly against a well-weathered stone wall at about 50 yards distance, doing this at different times of day and varying cloud/sunlight dispositions. Some bright stormlighting proved to be the best for this as well as the most aesthetic. it brought out all the textures and scars in the stone ...

Click to expand...

I find that kind of jumbly background (paddy7 mentioned tree bark which is similar) the worst possible target if I have to fine-tune diopter settings, and very tough if I have to find something on it. A peregrine sitting up on a building with nice clean lines can be seen from far greater distances than one blending in, as they do, with a rugged cliff face! If I have to adjust the diopter, something with straight lines and high contrast, like a road sign, or a distant pylon, is ideal (for me anyway). Birding most of the time in the city as I do, I can normally find some text or a distant building to get zeroed in on.

SeldomPerched said:

Any contender or contenders of yours for that position? I don't use it that much but the Victory 8x42 HT I bought from Troubadour is very fine and very bright (an AK design); also the 10x50 EL WB which has given me some unexpected birds - which I never managed to ID, but it is best from a position where the arms get a bit of external support, say from a window or behind a large box etc. Not to say it's unhandholdable but that way you get the best out of it.

Tom

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I think you already own or have tried all of those I would recommend! The 10x50 EL SV you own is superb and so is the 8.5x42, which I get to use regularly (my brother's). The latter in particular is a modern day classic and it's easy to see why the EL series have gained the market share that they have. The 7x42 Dialyt, P model, is still one of the nicest binoculars to look through, and although I only looked through the 8x42 HT very briefly at Birdfair a couple years back, I now have a fair amount of time with the earlier 8x42 FL (black) which I find very good indeed. The Noctivids I've tried (8x42 and 10x42) are in a comparable class to the other top alphas and I like the saturated Leica colours, especially here in the UK where the greyness leaches the colour out of everything. You also have the 8x56 FL which is possibly the format that is the most wonderful to look through hand-held, but which is sadly too bulky and heavy for the birding I do with the 8x magnification. Swarovski's 8x56 SLC is fabulous, but unlikely to be that much better than the big FL as to justify buying one.

NB. regarding Tringa's point about wandering diopters - my FLs, if not used for a while, will often need a slight readjustment. I don't really hold this against them, though, as my porros are the same. I've noticed that when I go abroad I will normally have to adjust the diopter as well. Most of the time only a slight adjustment is needed, and I probably end up bringing it back to the original setting sometimes, just like when you go back and forth with the focus sometimes to be certain of the point at which itis sharpest. I don't, however, seem to need to do this with Swarovskis. If that is achieved by spring tension, as Tringa mentions, then it works well.