8 x 40 Binoculars

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richardabeattie

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If I've got it right the light gathering advantage of 7 x 50s is not much use to older users and so for me 8 x 40 is probably a better bet. And I am not after a built in compass, image stabilisation or Blue tooth compatability whatever that means. On the other hand I suppose nitrgen filled and reasonably waterproof makes sense.

Oh and I'd like change from £100! So what does the forum advise?
 
I seem to "acquire" binoculars. The house has sea views so we need a pair in each room. I have a selection of 7 x 50s and these remain "good old faithfuls". The heavier pairs resist vibration and strong winds better; cheaper (and lighter) bins such as the plastimos seem not to last so long. I also have a couple of 8 x 30's: good general purpose bins. Very useful for race officer duties with a higher magnification than the 7 x 50s albeit with a smaller field of view. Ex military take a lot of hammering. Lots of choice for under £100; do not automatically discard Lidl's. I like my Opticron 10 x 42s for birding. Best bet is to try as many pairs as possible. You often get good deals at boat jumbles and by spending £50 or so on a professional service you can still come in under your budget. My absolute favourites are my canon 10 x 30 image stabilised. Even at around £300 (less on e bay) superb value for money and if I had to "de-clutter" to only one pair these are the ones I would keep. They work well afloat,for birding and boat spotting and general use.
 
Malabar

That's all very informative but it does not really tackle what I'm after which is
confirmation that 7 x 50 is no country for old men and that I can find some reasonable 8 x 40's without bells and whistles but which are not going to fill up with water as soon as I point them to windward. And which don't cost £300!
 
richardabeattie said:
Malabar

That's all very informative but it does not really tackle what I'm after which is
confirmation that 7 x 50 is no country for old men and that I can find some reasonable 8 x 40's without bells and whistles but which are not going to fill up with water as soon as I point them to windward. And which don't cost £300!
Click to expand...

Understood. As an OAP I often find the better light gathering characteristics of 7 x 50 over 8 x 40 to be of advantage, especially round dull old UK.
 
richardabeattie said:
Malabar

That's all very informative but it does not really tackle what I'm after which is
confirmation that 7 x 50 is no country for old men and that I can find some reasonable 8 x 40's without bells and whistles but which are not going to fill up with water as soon as I point them to windward. And which don't cost £300!
Click to expand...

The 7X50 is all to do with pupil size. As far as I am aware your pupil does no change with age.
 
Can someone explain what the relationship between 7 and 50, or 8 & 40. I mean why not 8x50. Or 9x100. Surely we want high magnification and great light gathering
 
The first number is the magnification, the second number is the diameter in mm of the large lens hence the relationship with light gathering. Ideally it might be argued that we all want max magnification and max light gathering, but the penalty is size and weight and what can be held steady. It is generally agreed that 7x50 are best on the water as being the best trade-off between performance and keeping the image steady enough to be useful. Much larger and steadying devices (either tripods or image stabilisers) become necessary.
 
The following is from Sky and Telescope magazine. So it confirms my understanding that 8 x 40 is what I need. So I say again - who can recommend a good but reasonably priced pair of 8 x 40s?

"7 mm is supposed to be the ideal maximum size for the exit pupil of binoculars or a telescope.

This is the reasoning behind the popular 7x50 "night glass" binocular. Divide its 50-mm aperture by its 7-power magnification and you get an exit pupil 7.1 mm across, just about right.

But it ain't necessarily so. Everybody is different.

Some of us have night-owl pupils that enlarge to nearly 9 mm in the dark; others don't make it to 4 mm. After young adulthood there's a gradual downward trend with age — slowly at first, then more rapidly from about age 30 to 60, then slowly again in your later years. But even among people the same age there's a good 3 mm of scatter, so that some 70-year-olds outdo some teenagers.

The problem is that if the exit pupil of a binocular or telescope is too large to fit into your eye, you lose some of the instrument's incoming light. Imagine your eye's greatly magnified iris covering a telescope's front end like a prop in a horror movie, diaphragming the instrument down to a smaller aperture. For example, when a 4-inch (100-mm) telescope is used at 10x, its exit pupil is 10 mm across. If your eye's pupil is only ¾ this size, you're only looking through ¾ of the telescope's aperture — it's acting as a 3-inch, not a 4-inch. Clearly, 10x is too low a power to use on a 4-inch telescope if you want to take advantage of its full light-gathering abilities.

Similarly, if you're in late middle age and have a maximum pupil size of only 5 mm, your 7x50 binoculars are acting as 7x35's, and those big 10x70s you've been thinking of buying might as well be 10x50s. "
 
Well it seems to me as definitely not an expert that a larger diameter binoculars will give you simply a bigger picture without redirecting the bins. So looking for eg. a boat that you can see with naked eye will be easier with larger bins as with smaller bins you will need to be more accurately pointed at the boat. Of course the higher magnification the smaller area you are looking at so this problem is magnified. As I understand it 7 or 8 magnification is about all you can cope with on a small boat because of boat movement. (also makes it easier to find things). Certainly 50mm are heavier and more bulky than 30mm.
For a fixed perhaps tripod installation higher magnification is good except again harder to find things. (or more sweeping around needed to find them)
I have never found actual light gathering to be a problem. good luck olewill
 
William_H said:
Well it seems to me as definitely not an expert that a larger diameter binoculars will give you simply a bigger picture without redirecting the bins. So looking for eg. a boat that you can see with naked eye will be easier with larger bins as with smaller bins you will need to be more accurately pointed at the boat. Of course the higher magnification the smaller area you are looking at so this problem is magnified. As I understand it 7 or 8 magnification is about all you can cope with on a small boat because of boat movement. (also makes it easier to find things). Certainly 50mm are heavier and more bulky than 30mm.
For a fixed perhaps tripod installation higher magnification is good except again harder to find things. (or more sweeping around needed to find them)
I have never found actual light gathering to be a problem. good luck olewill
Click to expand...
You may never have found light gathering to be a problem, but I assure you that when it happens, you will be grateful for having the best you could. It happened to us a couple of years ago in the Dovetief channel which is only partly lit at very late twilight, when my trusty old 7x50s played their part brilliantly. Even at over 70, my pupils will dilate to over 6mm in the dark.
 
I searched these, other forums and reviews when choosing my own bins. The reviews were not helpful, people generally liked whatever bins they had bought (prices ranged from £1k to £20). The forums produced a list of what people have and how they use them which is useful but didn't help me choose a specific pair. There was a PBO article a few years ago which gave a good overview of the important factors to consider when buying; I used that as a guide together with opinions from various astronomy forums where light gathering is an even bigger issue.

The light gathering capability and "exit pupil" size are only part of the night performance specification. The prism structure, glass type and lens coating are also very important. Uncoated lenses lose up to 5% of the gathered light at each change of refractive index (that's at every lens, air and prism junction). So a fully multi-coated system with a smaller object lens can pass more light to the eye than a partially coated system with larger object lens and bigger exit pupil.

With similar criteria to the OP I choses these:
http://www.microglobe.co.uk/pentax-8x40-pcf-wp-ii-water-proof-porro-prism-binocular-p-2604.html
Pros:
- Waterproof.
- Poro prism (this system loses less light than others but make the bins larger).
- Fully multi-coated lenses (loses less light than partially coated).
- Of the 3 most common glass types in use, these use the lowest light loss type.
- Very good eye relief. Very easy to adjust and one of the largest ranges I found.
Cons:
- Focus wheel is a bit stiff.
- Heavy, they are fine for the boat but I wouldn't want to wear them around my neck on a long walk.
- The neck strap supplied is scratchy and uncomfortable (but easily replaced by a neoprene one).
Other:
- They won't focus closer than 3m. Not an issue for boat use but if you want to use them for birdwatching and wildlife as well you won't be able to focus on the butterfly that just landed on your foot.


I've had them for 12 months and for use on the boat (which is what I bought them for) they have been very good.

For my criteria they are a good price/feature balance.
 
As many have said a 7 times magnification is considered the ideal for marine use.
I agree.

One thing not considered perhaps yet is image stabilisation.
With this one might be able to use 10 times mag.

Not sure how much it costs though!
 
As confirmation to what has been said before, I bought a pair of 10x50 Nikon Sporter EX binoculars. They are an excellent product, nice shape and weight ( coated, waterfprrof, etc) - BUT 10x50 is indeed too much for marine use. You need to jedi-master your body posture to use them - way too shaky for rockin' boats... nothing wrong with them, just not the best usage scenario...
 
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