Why are you keeping your 7x binoculars? (1 Viewer)

Pileatus said:

I used a Leica Ultravid 7X42 for many years and never once did I experience a more enjoyable DOF or FOV than I found with quality 8X bins. I think the mystique of 7X is out of whack with reality and is primarily based on the decrease in handshake due to the lower power. Heck, a 6X is almost image stabilized, something that fools the mind into believing all sorts of things. As it is, I find the DOF/FOV in my 8.5X42 Swarovision superior to any 7X I've encountered. The little 8X32 SV my wife owns has a very immersive FOV and its DOF is as good as it gets.

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The true FOV of many 7x binoculars is identical to that of 8x binoculars of the same manufacturer, due to limitations by the prism size. So these 7x may have an unpleasantly narrow apparent field of view. Regarding DOF, there is nothing a designer can do about it: It depends on power and exit pupil size, nothing else. At low power the DOF is always deeper than at higher power.

7x is a very universal magnification. The armies of almost the entire Warsaw Pact used 7x40 as their standard binocular.

Cheers,
Holger

Holger Merlitz said:

The armies of almost the entire Warsaw Pact used 7x40 as their standard binocular.

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Precisely! And where are they now???

Sancho said:

Precisely! And where are they now???

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A good one

The relationship between magnification and DOF is irrefutable. At 1X, our eyes do the best they can do to accommodate various distances, an ability that diminishes with age. As others have discussed before, I think the perceived DOF of any binocular is determined by three things: (1) the overall ability of the binocular to deliver a sharply focused image, (2) the magnification of the bin and, (3) the ability of the user's eye(s) to accommodate.

A dull binocular unable to deliver a crisp image at the focal point isn't going to have good DOF, regardless of magnification. Also, DOF implies gradual degradation from the focal point, not uniformity. Young, flexible eyes simply have a better chance of correcting as distance increases...hence a younger person might report great DOF that an older birder just can't see.

There's a lot to be said about 7X. Personally, I believe the reduction in handshake supersedes the increased DOF, especially for aging birders. I also believe the ideal general-purpose travel binocular would be an alpha 6X32. I'd buy a 6X32 Swarovision in a heartbeat! The stability of a well balanced 6X32 is simply amazing and the "loss" of magnification isn't as detrimental as one might think.

My accommodation isn't very good so the 7X42 has only one advantage for me, reduced handshake. My 8.5X42 SV probably shakes a bit more, but its across-the-field sharpness has resulted in less movement and fewer focus adjustments. Mathematically the 8.5X42 has less DOF than the 7X42, but that's not the point. I perceive, in the real world of birding, a less burdensome view in the SV. I call this the optical workload factor...or the OW factor. If bin A hurts less than bin B then I'm buying bin A. It's that simple and the reason us old folks save our pennies and buy the very best. It's also why the "95% as good" argument is specious, at best, especially to those of us with aging eyes.

Pileatus said:

There's a lot to be said about 7X. Personally, I believe the reduction in handshake supersedes the increased DOF, especially for aging birders. I also believe the ideal general-purpose travel binocular would be an alpha 6X32. I'd buy a 6X32 Swarovision in a heartbeat! The stability of a well balanced 6X32 is simply amazing and the "loss" of magnification isn't as detrimental as one might think.

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That would be a nice combination of power, size, portability, ease of use, etc. In fact, that would be the only binocular many people would even need. They would never need to buy another pair of binoculars. That's why it's never going to be made.

CloseFocus said:

That would be a nice combination of power, size, portability, ease of use, etc. In fact, that would be the only binocular many people would even need. They would never need to buy another pair of binoculars. That's why it's never going to be made.

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I think that is also why so many of the binoculars used by the armies of the world in the 20th Century, outside of the Warsaw Pact, were 6 x 30 porro prisms.

Bob

Holger Merlitz said:

The true FOV of many 7x binoculars is identical to that of 8x binoculars of the same manufacturer, due to limitations by the prism size. So these 7x may have an unpleasantly narrow apparent field of view.

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Cheers,
Holger

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I compare FOVs of binoculars on the same subject which is a tree line of tall coniferous trees with a tall Oak tree in the center. All the trees are in focus at infinity. 8º with a 7x42 is no different than 8º with an 8x42. But the view through the 7x42 is smaller.

Bob

I don't really see what the success of binoculars with the military tells us about their usability for birding.

A 7x binocular is good for birders that have difficulies with handshake, typically older people. And it is good for warbling and similar birding types, where a large field is important but a large mag. rather less important.

A 70 year old birder looking at a warbler 5 m away, that is as far as it can get from typical military binocular use.

Birding in open country is probably more similar to military use, but for open country birding, 10x is usally prefered, at least in Europe.

But then I am even not sure if I understand the reason military used a lot of 7x and 6x binoculars. Ok, they need a large FOV, but they also need to see things far away, for which a high mag would be better. Perhaps it had more to do with 7x and 6x binoculars being easier and cheaper to produce in reasonable quality?

What is modern military using btw, still predominantely 7x?

Holger Merlitz said:

The true FOV of many 7x binoculars is identical to that of 8x binoculars of the same manufacturer, due to limitations by the prism size. So these 7x may have an unpleasantly narrow apparent field of view. Holger

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Thanks for clearing that up for me. I had a 7x42 Leupold and always read that 7x provided a wider fov, but after I had it for a while I kept seeing specs of 8x bins online that had wider fov and was confused. I also felt that the Leupold 7x fov was a little narrower than I expected it to be when looking through it.

I got rid of my 7x, as I felt a little frustrated when learning to ID birds and found 8x aids me a little better. I still retain the 6x30 Yosemite and love the view in that little one. It is nice to have a more stable image, but for non-backyard birding I feel the better tool is the 8x for me since I am still learning ID skills.

dalat said:

I don't really see what the success of binoculars with the military tells us about their usability for birding.

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True. I only very rarely get shot at when birding. Tried 6.5x for a while, and although it was nice for relatively close-in birding, for anything further away, the images were just, well, too small! My SV 8x32 is as steady a bino as I´ve ever had for my hands, for the moment. Perhaps as I age more that will change. But as a previous poster implied, each to one´s own, the fun part is we can all choose what best suits us!

dalat said:

I don't really see what the success of binoculars with the military tells us about their usability for birding.

A 7x binocular is good for birders that have difficulies with handshake, typically older people. And it is good for warbling and similar birding types, where a large field is important but a large mag. rather less important.

A 70 year old birder looking at a warbler 5 m away, that is as far as it can get from typical military binocular use.

Birding in open country is probably more similar to military use, but for open country birding, 10x is usally prefered, at least in Europe.

But then I am even not sure if I understand the reason military used a lot of 7x and 6x binoculars. Ok, they need a large FOV, but they also need to see things far away, for which a high mag would be better. Perhaps it had more to do with 7x and 6x binoculars being easier and cheaper to produce in reasonable quality?

What is modern military using btw, still predominantely 7x?

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Florian,

I don't really know what the army's of the world are using now. Some 7 x 28 IF Roof Prism binoculars have been used in the Near East and have been discussed here in the past.

The 6 x 30 porro prism was in ubiquitous use throughout WWI and WWII although they were all IF. You are right. They were used because they had a wide FOV, were lightweight and easy to carry, easy to use and easy to make. Officers generally carried bigger, more impressive binoculars.

There is a thread here discussing the binocular that played a big part in the movie "The Bridge on the River Kwai" which expanded into one about binoculars which were used in movies.

http://www.birdforum.net/showthread.php?t=161217

Bob

dalat said:

Birding in open country is probably more similar to military use, but for open country birding, 10x is usally prefered, at least in Europe.

But then I am even not sure if I understand the reason military used a lot of 7x and 6x binoculars. Ok, they need a large FOV, but they also need to see things far away, for which a high mag would be better. Perhaps it had more to do with 7x and 6x binoculars being easier and cheaper to produce in reasonable quality?

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Militaries probably use low power binoculars because during strenuous physical activity they are easier to hold steady. Someone running from pothole to pothole trying not to get shot isn't going to waste too much time trying to pick out the delicate shading of a bird's feathers. They are perfect binoculars for getting a quick look at something and, coincidentally, great for birding in those situations where getting a quick ID is all one can hope for. I have a pair of 10X32 UV's that work great in the wide open spaces and barren ground cover of Arizona, but in Michigan, spotting a warbler in the shadowy underbrush of a forest canopy requires more hand to eye coordination and quick reflexes than resolving power.

For a quick id is a 8x,10x or even a 12x power binocular better. The strenght of a 7x power bin is its ability that one can watch birds through it for a long while before it gets too shaky. Far longer than you could with a bin of higher power. So for looking at birds a higher power is maybe better, but if you really want to observe birds a 7x power might be not a bad idea.
Also is the steadiness of a 7x bin an big advantage in cold or windy days. Or as you have to raise your bin to look at a bird high in a tree right above you.
I have to apologise for my bad english.

. The military use a variety of binoculars.
The 6×30 often with reticules was maybe the most common.
I think the fact that it can be handheld without shaking and it's fairly wide field with simple optics was the main reason. Also with uncoated optics it gave a reasonably bright image.

In Britain for some reason the British made Avimo 7×42 fixed focus was specified with long eye relief.
I think it can be used with glasses. But it was disliked because of its elbow design which meant one's head was raised 2 inches which is not a good idea if somebody is shooting at you. I think I would have used it upside down. it is still being used although probably more modern binoculars are also used.
I believe that some 8×42 roofs are also specified.

In Russia I think that as well as 6×30, 8×30 were popular.
Tank crews also sometimes used the 15×50 I think, image stabilised mechanical binocular which had a big compensation angle and apparently works quite well.
However, the way it works means that the actual aperture is about 35mm as only a part of the objectives are used at any one time.

I've seen British officers using personal small roof prism binoculars may be 8×21.

In World War II the British didn't have enough binoculars and there was a scheme where civilians lent whatever binoculars they had which were then categorised into several qualities and given out to the military. All sorts of magnifications and apertures were found.
In World War I there were still many Galileo field glasses used and I believe very strangely that the British had access to Zeiss prismatic binoculars.

Fujinon image stabilised binoculars such as the 14 x 40 are used in moving vehicles such as helicopters. They can be plugged into the electrical supply or used hand-held with 4 batteries.
There is also the night and day version with interchangeable eyepieces, normal optical and image intensifiers.

There are also Russian image stabilised monoculars that are used I think also by the British. One version I think takes about a minute for a flywheel to speed up for the stabilisation. It is noisy and weird.

There are technicians who service all these different binoculars in the field but sometimes they don't make such a good job of it although I would think with a 6×30 they were simple enough and robust enough to perform well with the servicing they had.

I've also met military Questar telescopes and Den Oude Delft Mirror telescopes of incredibly high quality.
Some of the Soviet tank scopes are apparently one 20th wave.

There were all sorts of elbow telescopes and other binoculars some using huge eyepieces some of which contain thorium.

Then there are the 7×50, 8×60, 10×80, 15×80 and larger binoculars of 100 mm, 120 mm, 150 mm, 180 mm, 200 mm, 250 mm, and 300 mm aperture of the refracting type.

A whole listing of military binoculars and scopes would be very long indeed.

As a big fan of the 6.5x/7x + 10x combo and owner of two great 8x binoculars, I feel qualified to share my opinion.

The biggest advantage of using a 7x is the speed with which an ID can be obtained.
This is the result of the vastly increased depth of field and the large FOV. If focused to medium distance, a roof like the Fury or Meopro 6.5x32 with their fast and light focusing knobs can be dialled into focus within fractions of a second. Their big FOV makes aiming a child's play and the low magnification not only delivers steady images for prolonged viewing, but also instantly after lifting the binocular.

If the FOV is imagined as a virtual, cone-shaped volume rather than a 145 m disc at 1000 m distance, it becomes obvious that the great angle of view and the great depth of field of a 6x/7x will provide MORE visual information than any 10x ever will.
More birds are
1) within the FOV (inside the outer walls of the cone)
2) sharp (inside the outer walls and inside the subvolume that's in focus)
3) rapidly dialled into sharpness
4) viewed interacting with other birds
than ever possible with any 10 binoculars.

The magnification difference of a 6.5x vs an 8x resembles the 8x vs a 10x.
I have found, though, that the shorter depth of field of the 8x causes some uncertainty where the focus really is, unlike a 10x where the sharp image appears at a very precise focus position.

In addition, I have made in vivo comparisons between a top 8x and a top 10x and concluded that the 10x offered no advantage in real use over the 8x, regardless of distance and detection of the smallest discernible details.

My final conclusion would be that a 6x to 7x roof is indispensible for close range birding, and very usable for average birding situations. A 10x will deliver what the 6x/7x won't, but that also goes for a good 8x/8.5x.
The 8x will serve better substituting a 10x than substituting a 6x/7x.

//L

In both of his books about identifying Hawks in flight in the section about "Optics for Hawk Watching" Jerry Liguori stated he used 7 x 42 binoculars because of their wide field of view. He used Zeiss 7 x 45 Night Owls from 1994 to 2008 when he switched to a 7 x 42 Victory FL. He noted that others preferred 8 x 42 or 10 x 42. He also stated, strongly, that whatever binocular one used it should be "high quality."

Bob

Pileatus said:

The relationship between magnification and DOF is irrefutable. At 1X, our eyes do the best they can do to accommodate various distances, an ability that diminishes with age. As others have discussed before, I think the perceived DOF of any binocular is determined by three things: (1) the overall ability of the binocular to deliver a sharply focused image, (2) the magnification of the bin and, (3) the ability of the user's eye(s) to accommodate.

A dull binocular unable to deliver a crisp image at the focal point isn't going to have good DOF, regardless of magnification. Also, DOF implies gradual degradation from the focal point, not uniformity. Young, flexible eyes simply have a better chance of correcting as distance increases...hence a younger person might report great DOF that an older birder just can't see.

There's a lot to be said about 7X. Personally, I believe the reduction in handshake supersedes the increased DOF, especially for aging birders. I also believe the ideal general-purpose travel binocular would be an alpha 6X32. I'd buy a 6X32 Swarovision in a heartbeat! The stability of a well balanced 6X32 is simply amazing and the "loss" of magnification isn't as detrimental as one might think.

My accommodation isn't very good so the 7X42 has only one advantage for me, reduced handshake. My 8.5X42 SV probably shakes a bit more, but its across-the-field sharpness has resulted in less movement and fewer focus adjustments. Mathematically the 8.5X42 has less DOF than the 7X42, but that's not the point. I perceive, in the real world of birding, a less burdensome view in the SV. I call this the optical workload factor...or the OW factor. If bin A hurts less than bin B then I'm buying bin A. It's that simple and the reason us old folks save our pennies and buy the very best. It's also why the "95% as good" argument is specious, at best, especially to those of us with aging eyes.

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I like your post, and it has many things that we can address about sizes
and how they work. I do look at any recommendation made on this forum
should include those with average eyesight. That will include those wearing
eyeglasses and those without.

When bringing in issues relating to age, such as shakiness, poor accommodation,
eyeglass, varifocal, trifocal, etc., that may be why a 7X binocular may have a place.
But the choices are getting to be few. 7x42's are available, but is there a
good choice in 7x32?

I look at the 8 or 8.5X42 binocular to be the best all around choice.
The 42mm objective, just gives a larger, bigger, better view, and helps
you center the object you are looking at.

The 32mm, has its limitations for those with some vision issues.

Jerry

Excellent thread, one of the best I've come across. :t:

Would someone like to add this info - thanks. How's the Nikon 7x35 - Action/Aculon or EX - in woodland - brightness, depth of field, usable field of view, handling? Also, if possible, compared with a 6/6.5x, with any other 7x.

Thanks a lot for your comments!

CloseFocus said:

Militaries probably use low power binoculars because during strenuous physical activity they are easier to hold steady.

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This is something I did not think about... Another point I did not think of is the advantage of lower mags in low light, I guess that was certainly sth. important for military use, although today they probably use better toys when it's dark.

dalat said:

Thanks a lot for your comments!

This is something I did not think about... Another point I did not think of is the advantage of lower mags in low light, I guess that was certainly sth. important for military use, although today they probably use better toys when it's dark.

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Yes, better, more expensive toys. I'm almost tempted to join the army to get to play with them, but birding in Afghanistan doesn't fit my schedule at the moment.