Hi All,
While on the subject of binoculars, I am wondering whether 10 x 42 is the best magnification x lens diameter combination for gloomy forest conditions or other low light situations where the quarry is not more than about 30m away from the observer, and magnification is not the major requirement.
Would optically equivalent (in quality) 7 x 50 give better light sensitivity and colour discrimination than say 10 x 42 or 10 x 50 ?
Close focus distance and rapid focus also relevant, as well as waterproofness in rainy humid conditions if not for scuba diving.
Any suggestions?
Cheers
Michael ===============================
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Peter et al,
Firstly, my apologies if this rambles a bit and covers some items already explained. I started composing it before some of the later postings. The thread is active enough that it presents a moving target.
I am also an astronomer (“amateur”, in the same sense that most members of this list would be amateur birdwatchers, i.e. do not engage in it as a paid profession) and have been watching this thread with interest. I would like to add my bit – starting with the suggestion that most of the light enters through the centre portion of the objective. I suspect your astronomer was attempting to point out that the increase in light gathered is proportional not to the diameter of the objective but to the area of the objective and proportional to the square of the diameter.
Consider an objective 42 mm in diameter collecting 1 unit of light. Increasing the diameter to 50 mm is like adding a 4 mm wide ring of extra glass. The area of the objective is 50^2/42^2 = 1.42 times greater, now collecting 1.42 units of light. of this, 1 unit or 70% is collected by the inner 42 mm, and the remaining 30% is collected by the 4 mm wide “ring” of extra glass.
The next bit in the optical train is the prism. There are various types which I won’t go in to except to say that one reason very cheap binoculars are is that the manufacturers use a prism too small for the job, resulting in vignetting. This is familiar to the photographers among us. Basically it means the edge of the field of view receives less light than the centre.
The next bit in the equation is the eyepiece or ocular. It is essentially a magnifying glass to magnify the image that is formed by the objective. There are various designs used my manufacturers, all with there good and bad points. The magnification is equal to the focal length of the objective divided by the focal length of the eyepiece. All else being equal a higher magnification means a dimmer image as you are trying to spread a smaller amount of light (from a smaller part of the image formed by the objective) over the same area (the eyepiece’s apparent field of view.) This means 10X42s will give a dimmer view than 8X42s.
Much has been said about exit pupils. This is the image of the objective, formed by the eyepiece, and it lies a short distance outside the binoculars, behind the eyepiece. This distance is known as the “eye relief” and depends primarily on the eyepiece focal length, but also on the eyepiece design. Shorter focal length (higher magnification) means shorter eye relief, which may be a problem if you wear glasses. The diameter of the exit pupil is equal to the objective diameter divided by the magnification. Theoretically all the light collected by the objective, (42 or 50 or whatever mm in diameter) is “funnelled down” to the diameter of the exit pupil, then into your eye making the image brighter than if seen by the naked eye alone, which only utilises the light collected by the eye’s pupil, normally never more than 7 mm in diameter and usually considerably less. Because of other factors this increased brightness is not readily noticeable in normal daylight viewing, but becomes apparent under low light conditions. Turn your binoculars to a starry sky to gain a good appreciation of this.
The final bit is the eye itself. After all of the above, the light still has to get in to your eye through the pupil, which varies in diameter depending on the amount of light entering the eye. It is generally accepted that the maximum pupil diameter of a fully dark adapted eye is 7 mm. For this reason many older binoculars were designed to achieve a 7 mm exit pupil to match, hence the almost ubiquitous 7X50s. the important point to note here is DARK ADAPTED. Think looking for the silhouette of a ship against the ocean in the middle of the Pacific ocean with only the light of the stars. This is when young healthy eyes can open up to 7 mm. In most practical birding situations, even a rainforest understory on a cloudy day, there is way more light than that, and we are deliberately trying to make it brighter by using the best combination of aperture and magnification. I see no need to go for an exit pupil of more than 5 mm. If you want 10X magnification then 10X50s are OK. 8X40 should give similar brightness. the reduction in lens diameter means the rest of the instrument, both body and internal prisms, can also be smaller with a significant reduction in weight.
Close focus is one consideration that is very important for birders but rarely presents a problem for other users such a sailors, sports watchers and astronomers.Focusing depends on a mechanical system to vary the distance between the objective and the eyepiece and has nothing to do with the optical specification. Close focus is achieved by moving the eyepiece further away from the objective.
I had a $200 pair of 10X50s which were great for astronomy but when I took up birding I quickly realise their limitations. Heavy, smaller field of view and unable to focus closer than about 12 metres. I now use a $250 pair of William Optics 8X42 SEMI-APO with 2.5 metre close focus and weighing 675 gm. The optical quality is very good, but obviously not in the class of Swarovski or Leica, but I consider them excellent value for money.
Thanks Lloyd, I’ll give that carrying style a try.
You’ve reminded me that another feature claimed to be misinterpreted by birders as shallow depth of field is “fast” focus wheels.
I found this myself when I changed to a pair that requires far less turning to focus. I actually misinterpreted it as being less sharp than the previous pair, because I wasn’t used to having to be so careful when focusing.
Peter Shute
Peter,
Yes, I just put the strap over my should and let them hang down from there. They sit comfortably from there if I am not moving fast. I can hold them with my left elbow against the body if needed. If I have to move fast or walk some distance, I put the strap from the shoulder over my head as well with the strap across my chest, when they sit high under my left arm which is quite comfortable. I have never been a fan over putting the strap over my neck – the weight on the neck gets rather unbearable after a few hours – also you have to hold them with one hand if you are walking fast.
Regarding depth of field, this was really brought home to me when I bought the 12x50s. There is just a slither in focus and you only had to move the focusing wheel a millimetre or so for it to go out of focus. Comparing it in a photographic sense, it was like using f2 with the 12x50s as against f16 with the 7x42s. I would be sure that it is not mistaking field curvature for depth of field.
Lloyd Nielsen
Peter Shute wrote:
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Lloyd, when you say you sling them over your left shoulder, do you mean they hang straight down from there, or is the strap diagonally across your chest so the binoculars are on your right side?
I also find interesting the comments you and several others have made about depth of field. I’ve read many arguments about this in other forums, with some saying they can’t see how manufacturers can really vary it.
Some claim that people are mistaking field curvature (if that’s the right term) for depth of field. I.e. The focus distance is closer to the observer at the edge than in the centre of the view. If that’s the case then the most expensive pairs with a flat field would have the worst apparent depth of field.
I haven’t owned or tried enough pairs to know if this is correct. All mine have been very curved.
Peter Shute
Verry Interesting.
Swarovski, Zeiss and Leica 10×42 weigh the same as their current 8×42 models.
10x50s are much heavier.
After I quit the booze and took my Parkinsons pills, holding the 10 x bins still enough to focus wasn’t a problem. Most Oz birders I know use 10 x 42 (Exceptions include two Poms, top birders, one uses 8×42, the other 7×50 for pelagics). The table referred to by Dave Torr is interesting, confirms that 8×42 transmit more light to he eye than 10x42s. Maybe that is why the 8×42 suit the generally more gloomy conditions in the UK, although I have birded there many times and dont have a problem with the 10x.
The harness is a good idea. Waning vision is bad enough, developing a hunch back (? “binocular back” ) as well would be terrible.
Thankyou all for your replies, obviously the go is to test them out at a local bino store then import the best at huge savings from California. Unless the locals will deal of course.
Insincerely yours
Michael
It seems obvious that there’s no point having binoculars with a exit pupil bigger than your own. The extra light should be wasted because it doesn’t even enter your eyes.
But I once read a forum posting that suggested this isn’t the whole story. The poster (an astronomer) claimed that because a larger proportion of the light transmitted through binoculars enters them through the central portion of the objectives than the outer portion, big ones are brighter even for small pupils. I don’t understand it, and it could be nonsense, but it’s worth checking for yourself before abandoning big binoculars.
Peter Shute
Hi all, yes I too found the article referenced by Dave Torr to be useful. In particular the info about how age affects the optimum specification of bins required per individual was something I hadn’t heard before. I too am thinking about some new bins “at some stage”, and being an old bloke of nearly 76 this has some importance in my choice.
I am considering replacing my old Leica 10×42 BA’s with either some new, as I understand it, lighter BN Leicas, or some of the yet to be released Swarovski EL 10×50’s. My experience with the Leicas are that they are heavy for their size and at one time the focussing mechanism jammed before getting down to close focus. (This was subsequently repaired at great expense because the local agent wouldn’t cover the cost under warranty).
When the Swarovski bins first came out I tried them and found them to be much brighter ( and lighter) than my Leicas, and this comment also applies to my Leica scope vs the corresponding Swarovski, much brighter in fact. I have contacted Bintel about the EL’s and they have given me a price with availability in April, and I have Adelaide Optical on a similar request. I’ll advise you once the info comes to hand. In the meantime if anyone has any further info which might influence my choice it would be most welcome.
On a different note, I too have just ordered a harness to take the weight off my neck.
Cheers, Tony
I am always interested in communications on this list regarding binocular magnifications. In the UK the most popular magnification is 8×40 or 8×42 and 10x are not much used. I realise that birding in Aus is a bit different to birding in the UK but any delusions I had about you all being so fit and macho that you could carry heavy 10x bins with ease has just been dispelled by the recent “harness” thread!
Often 10x binoculars are so heavy that they are hard to hold steady enough to get any advantage from the extra magnification. A harness can help with carrying but when actually using them you really need a tripod or a Finnstick. (I have only ever seen the latter in Finland – it is a T shaped piece of wood which you hold at waist height and use to support the binoculars at eye height – it really works!) The only time I could see that 10x might be really useful is if you are, say, sea-watching, and do not have a scope. In these kind of conditions, putting heavy bins on a tripod can be quite a revelation – the world suddenly gets much sharper! Photographers use a tripod for good reason.
(Our first pair of “real” birdwatching binoculars were Swift Audubon 8×42 which were huge and heavy – a tripod or more usually, a handy fencepost or rock, made a lot of difference to the sharpness of the image)
For gloomy forest conditions then it is the objective size rather then magnification which is important, and also particularly the depth of field, plus close focussing and number of turns to focus.
However, the objective size of course also increases the weight, but it is worth noting that due to improvements in technology the light gathering power of bins has improved a lot over the last 20 years and it may no longer be necessary to use x50 in low light. A modern 10×40 will be as bright as an older 10×50.
And unfortunately, the more you pay, the better the bins are in low light – though the marginal benefit soon starts to get very costly!
And as a footnote, Nikons are often reckoned to be very “bright” – i.e. gather a lot of light.
The article referenced by Dave Torr is really very interesting and covers material I have never seen before – however, it neglects to mentions depth of field as an important characteristic. This is possibly because it is rarely mentioned by manufacturers, so it is hard to find out how good a particular model is, however good reviews will cover it.
Peter and Rosemary Royle Wales, UK
Tick a few for me while you are there, Tim.
Cheers,
Carl
Couldn’t agree more Carl, about being broad-brushed. I was almost going to qualify my statement by saying exactly that
Instead I used term “my opinion” which should read “please don’t take this message seriously” or more perhaps more appropriate”please ignore”. (The last message I wrote to birding-aus – prior to this one – someone wrote back to me and said “Not much work on at work today Tim”.) As you say (to totally contradict myself) there are some super 10×50 binos around, some smallish and light.
Aside from that, heading to WA tomorrow morning (Dryandra and Two Peoples Bay), so not too much to complain about.
Cheers,
Tim
________________________________________ Sent: Tuesday, March 08, 2011 5:48 PM Cc: Michael Hunter; birding-aus@vicnet.net.au
Tim,
I think you are using a rather a broad brush here. I use a pair of Pentax 10×50 DCF ED and manage to carry them all day with no problem, despite an arthritic neck and back. I use a harness to carry them and sometimes even use a double harness to carry a DSLR with a tele lens no problem. My Pentax 10×50 are not much bigger than my old 8×42 Pentax. They weigh in at 855g which compared to say Swarovski’s top line 8×32 which is 832g or Leica Ultravid 8×40 at 790g, are not much of a load. The Pentax are also within a few millimetres in size of the Leicas and actually smaller than the Swaros
I also have a pair of Pentax 8×32 DCF EDs, which I thought were the bee’s knees, but I am not even sure where they are as it is so long since I used them. The 10x50s have become my first choice.
Binocular technology is advancing fairly rapidly, with some manufacturers greatly reducing size and weight of their bins, so one can not dismiss all big bins out of hand. Prospective buyers need to compare the various sizes to see which suits them the best, not just rely on others opinions. I did, which is why I have the bins I have.
Cheers,
carl Clifford
Hi Michael,
In my opinion for decent ‘birding’ i.e. walking around with a pair of binos birdwatching, there are only two – possibly three – real options for binoculars, regardless of conditions:
. 10 x 40 (or 42) – good magnification, so requires a little precision and practice i.e. to see birds in flight, so can sometimes be awkward in forests / closed bush – but perfect for open environ and most birding conditions. Any reasonable pair will work o.k. in gloomy light.
. 8 x 40 (or 42) – smaller in size than above and has less magnification, but perfect for forest conditions i.e. to see birds in flight through trees. Good for close range. Any reasonable pair will work o.k. in gloomy light.
Any larger than this, such as x 50 etc, size becomes just too awkward and cumbersome (even creating neck problems) for birding. There are of course exceptions to the rule. Some people just like them, enjoying the extra contrast and image brightness with the top-end binos (such as Leica), or have a strong neck, such as rugby playing birders. Larger binoculars can also be worthwhile if they are linked to a specific task, such as birding from a wetland bird-hide.
Personally (apart from 10 x 40 or 8 x 40) I’m also quite partial to 8 x 32 – small, compact, easy to use, and they’re great for casual stroll in the bush, particularly your own patch, where you know most of the birds, so exact feature identification is not that important. However I’d only recommend a good pair.
In essence when buying a pair of binoculars, purchasing a pair of x 50 because they’re slightly better when glooming ignores a dozen other aspects of binoculars when birding, such as size, weight, focus, ease of use, accessibility and even aesthetics (for example do you really want to walk around with a large and silly looking pair of binos around your neck).
Cheers,
Tim Dolby
Tim,
I think you are using a rather a broad brush here. I use a pair of Pentax 10×50 DCF ED and manage to carry them all day with no problem, despite an arthritic neck and back. I use a harness to carry them and sometimes even use a double harness to carry a DSLR with a tele lens no problem. My Pentax 10×50 are not much bigger than my old 8×42 Pentax. They weigh in at 855g which compared to say Swarovski’s top line 8×32 which is 832g or Leica Ultravid 8×40 at 790g, are not much of a load. The Pentax are also within a few millimetres in size of the Leicas and actually smaller than the Swaros
I also have a pair of Pentax 8×32 DCF EDs, which I thought were the bee’s knees, but I am not even sure where they are as it is so long since I used them. The 10x50s have become my first choice.
Binocular technology is advancing fairly rapidly, with some manufacturers greatly reducing size and weight of their bins, so one can not dismiss all big bins out of hand. Prospective buyers need to compare the various sizes to see which suits them the best, not just rely on others opinions. I did, which is why I have the bins I have.
Cheers,
carl Clifford
Hi Michael,
In my opinion for decent ‘birding’ i.e. walking around with a pair of binos birdwatching, there are only two – possibly three – real options for binoculars, regardless of conditions:
. 10 x 40 (or 42) – good magnification, so requires a little precision and practice i.e. to see birds in flight, so can sometimes be awkward in forests / closed bush – but perfect for open environ and most birding conditions. Any reasonable pair will work o.k. in gloomy light.
. 8 x 40 (or 42) – smaller in size than above and has less magnification, but perfect for forest conditions i.e. to see birds in flight through trees. Good for close range. Any reasonable pair will work o.k. in gloomy light.
Any larger than this, such as x 50 etc, size becomes just too awkward and cumbersome (even creating neck problems) for birding. There are of course exceptions to the rule. Some people just like them, enjoying the extra contrast and image brightness with the top-end binos (such as Leica), or have a strong neck, such as rugby playing birders. Larger binoculars can also be worthwhile if they are linked to a specific task, such as birding from a wetland bird-hide.
Personally (apart from 10 x 40 or 8 x 40) I’m also quite partial to 8 x 32 – small, compact, easy to use, and they’re great for casual stroll in the bush, particularly your own patch, where you know most of the birds, so exact feature identification is not that important. However I’d only recommend a good pair.
In essence when buying a pair of binoculars, purchasing a pair of x 50 because they’re slightly better when glooming ignores a dozen other aspects of binoculars when birding, such as size, weight, focus, ease of use, accessibility and even aesthetics (for example do you really want to walk around with a large and silly looking pair of binos around your neck).
Cheers,
Tim Dolby
Couldn’t agree more Carl, about being broad-brushed. I was almost going to qualify my statement by saying exactly that
Instead I used term “my opinion” which should read “please don’t take this message seriously” or more perhaps more appropriate”please ignore”. (The last message I wrote to birding-aus – prior to this one – someone wrote back to me and said “Not much work on at work today Tim”.) As you say (to totally contradict myself) there are some super 10×50 binos around, some smallish and light.
Aside from that, heading to WA tomorrow morning (Dryandra and Two Peoples Bay), so not too much to complain about.
Cheers,
Tim
________________________________________ Sent: Tuesday, March 08, 2011 5:48 PM Cc: Michael Hunter; birding-aus@vicnet.net.au
Tim,
I think you are using a rather a broad brush here. I use a pair of Pentax 10×50 DCF ED and manage to carry them all day with no problem, despite an arthritic neck and back. I use a harness to carry them and sometimes even use a double harness to carry a DSLR with a tele lens no problem. My Pentax 10×50 are not much bigger than my old 8×42 Pentax. They weigh in at 855g which compared to say Swarovski’s top line 8×32 which is 832g or Leica Ultravid 8×40 at 790g, are not much of a load. The Pentax are also within a few millimetres in size of the Leicas and actually smaller than the Swaros
I also have a pair of Pentax 8×32 DCF EDs, which I thought were the bee’s knees, but I am not even sure where they are as it is so long since I used them. The 10x50s have become my first choice.
Binocular technology is advancing fairly rapidly, with some manufacturers greatly reducing size and weight of their bins, so one can not dismiss all big bins out of hand. Prospective buyers need to compare the various sizes to see which suits them the best, not just rely on others opinions. I did, which is why I have the bins I have.
Cheers,
carl Clifford
Hi Michael,
In my opinion for decent ‘birding’ i.e. walking around with a pair of binos birdwatching, there are only two – possibly three – real options for binoculars, regardless of conditions:
. 10 x 40 (or 42) – good magnification, so requires a little precision and practice i.e. to see birds in flight, so can sometimes be awkward in forests / closed bush – but perfect for open environ and most birding conditions. Any reasonable pair will work o.k. in gloomy light.
. 8 x 40 (or 42) – smaller in size than above and has less magnification, but perfect for forest conditions i.e. to see birds in flight through trees. Good for close range. Any reasonable pair will work o.k. in gloomy light.
Any larger than this, such as x 50 etc, size becomes just too awkward and cumbersome (even creating neck problems) for birding. There are of course exceptions to the rule. Some people just like them, enjoying the extra contrast and image brightness with the top-end binos (such as Leica), or have a strong neck, such as rugby playing birders. Larger binoculars can also be worthwhile if they are linked to a specific task, such as birding from a wetland bird-hide.
Personally (apart from 10 x 40 or 8 x 40) I’m also quite partial to 8 x 32 – small, compact, easy to use, and they’re great for casual stroll in the bush, particularly your own patch, where you know most of the birds, so exact feature identification is not that important. However I’d only recommend a good pair.
In essence when buying a pair of binoculars, purchasing a pair of x 50 because they’re slightly better when glooming ignores a dozen other aspects of binoculars when birding, such as size, weight, focus, ease of use, accessibility and even aesthetics (for example do you really want to walk around with a large and silly looking pair of binos around your neck).
Cheers,
Tim Dolby
Hi Michael,
In my opinion for decent ‘birding’ i.e. walking around with a pair of binos birdwatching, there are only two – possibly three – real options for binoculars, regardless of conditions:
. 10 x 40 (or 42) – good magnification, so requires a little precision and practice i.e. to see birds in flight, so can sometimes be awkward in forests / closed bush – but perfect for open environ and most birding conditions. Any reasonable pair will work o.k. in gloomy light.
. 8 x 40 (or 42) – smaller in size than above and has less magnification, but perfect for forest conditions i.e. to see birds in flight through trees. Good for close range. Any reasonable pair will work o.k. in gloomy light.
Any larger than this, such as x 50 etc, size becomes just too awkward and cumbersome (even creating neck problems) for birding. There are of course exceptions to the rule. Some people just like them, enjoying the extra contrast and image brightness with the top-end binos (such as Leica), or have a strong neck, such as rugby playing birders. Larger binoculars can also be worthwhile if they are linked to a specific task, such as birding from a wetland bird-hide.
Personally (apart from 10 x 40 or 8 x 40) I’m also quite partial to 8 x 32 – small, compact, easy to use, and they’re great for casual stroll in the bush, particularly your own patch, where you know most of the birds, so exact feature identification is not that important. However I’d only recommend a good pair.
In essence when buying a pair of binoculars, purchasing a pair of x 50 because they’re slightly better when glooming ignores a dozen other aspects of binoculars when birding, such as size, weight, focus, ease of use, accessibility and even aesthetics (for example do you really want to walk around with a large and silly looking pair of binos around your neck).
Cheers,
Tim Dolby
Michael,
As a rule of thumb, the bigger the front end, the brighter the image and the better the glass the brighter the image. The higher the mag , the narrower the field of view, which at short range may not be that much of an issue. To meet the rest of your criteria, I think you would have to look at military or marine specification bins. Steiner, with their Military R range, seem to have a lot of the market, though you might like to look at the Pyser-SGI range http://www.pyser-sgi.com/images/thumbnails/Defence_Files/Military Binoculars.pdf They are suppliers to the UK military. Also have a look at http://www.quicktest.co.uk/military_binoculars.htm for some alternatives. As for scuba diving, I suggest sonar.
Cheers,
Carl Clifford
Hi All,
While on the subject of binoculars, I am wondering whether 10 x 42 is the best magnification x lens diameter combination for gloomy forest conditions or other low light situations where the quarry is not more than about 30m away from the observer, and magnification is not the major requirement.
Would optically equivalent (in quality) 7 x 50 give better light sensitivity and colour discrimination than say 10 x 42 or 10 x 50 ?
Close focus distance and rapid focus also relevant, as well as waterproofness in rainy humid conditions if not for scuba diving.
Any suggestions?
Cheers
Michael ===============================
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I use a pair of Nikon Monarch 8.5 x 56 bins, which are very heavy (getting back to the previous thread?) but are astounding in low light conditions, like turning on the lights. During the day, of course, a lot of the light coming from the eyepiece gets spilled on my iris, meaning I end up carrying more than I need.
They’re rugged and pretty waterproof, and not dramatically expensive. The close focusing does leave something to be desired though.
Bill
You might want to read http://boca.org.au/component/docman/doc_download/500-best-binocular-for-youwhich has a lot of information on light gathering and the ideal ratio according to your age!
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