Binoculars Again -- 7x30 vs 7x50

[Dockhead]

Another thread on binos has got me thinking again about acquiring some compass binos, something I haven't had since I broke my crappy Fuji Mariners a few years ago.


I have a few pairs of 7x50's on board, and my go-to binos are my Dad's old Fuji Meibos, which are optically exquisite -- could hardly wish for better.


But I need one with a compass. In terms of price/quality the Fuji Polaris ones are probably best, but those things are a brick. I like the Steiner Commander form factor better, even if they are more expensive than the Fujis and not as good optically.



The Steiner Commander used to be made in not only 7x50, but also 7x30, and that got me thinking -- why not make the form factor even better, and go with a pair of 7x30's? I've got the Meibos for any case where I need the extra light gathering. I can hardly think of a case where I would need BOTH max light gathering AND the compass -- even on a dark night, if I'm taking bearings to a fishing boat's nav lights, say, the 7x30's will be fine. And in daylight, 7x30 is fine.


Does anyone see a flaw in my plan? Anyone using 7x30's?


Is there any other drawback to them? Is the field of view less?

[s/v Jedi]

Flaws, yes.

I do not want a lineup of binoculars getting in the way... have enough stuff already: just one which can do it all. After the debacle with our Seiners, we're pretty happy with out Nikons now. Got it all and pleasantly priced.

[Dockhead]

Originally Posted by s/v Jedi

Flaws, yes.

I do not want a lineup of binoculars getting in the way... have enough stuff already: just one which can do it all. After the debacle with our Seiners, we're pretty happy with out Nikons now. Got it all and pleasantly priced.

Well, I won't reduce the quantity of binos on board, by going with 7x50. I'll still have the Meibos around.


What was your "debacle" with Steiners?

[Marathon1150]

Originally Posted by Dockhead

Is there any other drawback to them? Is the field of view less?

The field of view of the 7x35 will be wider than the 7x50's. But, the exit pupil of the 7x50's will be bigger (typically 7mm vs 5mm for the 35's). This is why the 50's are "brighter" - more light gets through the optics.

[tkeithlu]

Whoa, Marathon. The reason 7x50s are "brighter" is the ratio of the diameter of the objective lens to the magnification, not the size of the exit lens. 7x50s collect more light at night than your eyes do, so you can see dim objects better with your binoculars than with your Mk.I eyeballs. 7x50s have a 7.1 ratio, 7x35s, usually the choice of bird watchers, have a 5.0 ratio.

[FastTrout]

Bigger objective is always better.

If you don’t need the compass there are much better options like vortex, better bang for the buck and they also have a far better warranty.

[Marathon1150]

Originally Posted by tkeithlu

Whoa, Marathon. The reason 7x50s are "brighter" is the ratio of the diameter of the objective lens to the magnification, not the size of the exit lens. 7x50s collect more light at night than your eyes do, so you can see dim objects better with your binoculars than with your Mk.I eyeballs. 7x50s have a 7.1 ratio, 7x35s, usually the choice of bird watchers, have a 5.0 ratio.

Thanks, but, the size of the exit pupil is not the same as the size of the eyepiece (exit) lens. The exit pupil is smaller than the eyepiece lens. Hold the binoculars up to the light and look into the eyepiece lenses. There is bright circle of light - this is the "exit pupil" diameter - it is smaller than the diameter of the eyepiece lens and is determined by the size of objective lens, as you note. Normally, the exit pupil for 7x50 binoculars is 7mm (as per your comment) and for 7x35 it is 5mm. So I'm sticking with my point - 7x50 binoculars are brighter because the larger objective lens allows more light in and produces a larger exit pupil. Astronomy types believe that past a certain age it doesn't matter because aging eyes, like mine, may not be able dilate to 7mm. So "brightness is a function of objective lens, exit pupil and eyeball age.

[a64pilot]

Originally Posted by FastTrout

Bigger objective is always better.

If you don’t need the compass there are much better options like vortex, better bang for the buck and they also have a far better warranty.

Not necessarily, it has to be usable, the idea of a bigger objective lens is always better is widely thought to be true, and for that reason many, many budget rifle scopes and bino’s have objective lenses that are bigger than the rest of the optics’s can use.

Also the age group we are most likely talking about here, an exit pupil diameter above about 5 mm isn’t likely to be useful. Now if we were 20 yr old, then our pupils could likely dilate up to about 8 mm or so, but about 40ish and older about 5 is average.

The 7x50 format is tough to beat, you can go smaller and lighter, but most likely it’s going to suffer in light gathering.
Now high quality 7X30 will most likely be brighter than say a Tasco 7x50, high quality glass and coatings will make up for a lot, but the same high quality lenses on a 7x50 will of course be better.

US Military uses Steriner 7x50’s for its scouts and has for decades, how long I don’t know.

[rslifkin]

If you like the Fuji binoculars and want lighter and cheaper, get the mariner series ones. I've got a set with compass. They're not quite as bright as the Polaris and the optics aren't quite as good, but they're still very good. And they're fairly cheap and pleasantly lightweight.

[Dockhead]

Originally Posted by rslifkin

If you like the Fuji binoculars and want lighter and cheaper, get the mariner series ones. I've got a set with compass. They're not quite as bright as the Polaris and the optics aren't quite as good, but they're still very good. And they're fairly cheap and pleasantly lightweight.

I had a Fuji Mariner, and my experience was different from yours. I thought it was horrible plastic toy, and it duly broke. I threw it in the trash without regret. The optics were horrible, the compass was off by 10 degrees in either direction. Made in China; nothign in common with the Polaris. Bleh. YMMV.

[rslifkin]

You know, I've never actually confirmed the compass accuracy on the things. I've only used it as a reference when handing them to someone else to look at something. They do feel a bit cheap, but they are, so they're usually my first grab unless I need something really good. Mostly because they're no big loss if they get damaged / dropped / broken.

[a64pilot]

Exit pupil diameter is one factor determining how bright optics are, quality of lenses and prisms is another of course, but assuming same quality lenses a 7x30 will have a exit pupil of 4.2 mm, it’s simple math, a 7x50 will have a diameter of 7.1

Now as we age our pupils get less flexible and can’t dilate as much as when we were young, but even in my 60’s I can tell the difference between 7x30 and 7x50 in dim light
https://imaging.nikon.com/lineup/spo...c/basic_05.htm

Ideally you need to try both in low light conditions in a brightly lit store 7x30’s will look quite good.

The 7x50’s only really come into play in low light conditions, even a heavy overcast foggy day is low light.

[s/v Jedi]

Originally Posted by Dockhead

What was your "debacle" with Steiners?

pieces were falling off and they would not honor warranty unless I would take it around the world back to Holland, so I basically had to throw away a 700 Euro piece of ...

[freshalaska]

I’ve been very happy with my 10x42 Leica. Very rugged and supreme clarity.
Expensive and will last probably 50 years, maybe more. Had mine now about 18 years.

[Jammer]

Originally Posted by Dockhead

Does anyone see a flaw in my plan? Anyone using 7x30's?

Is there any other drawback to them? Is the field of view less?

I have the Fujinon Polaris in 7x50. They are big and expensive and while I love the optics they are awkward to have around and too expensive to leave on the boat. So, I also have some cheaper 8x32 penta prisms (Fujinon KF, recently discontinued I believe). They don't have a compass.


Reviewing what is available, the 7x30s on the market new and used, with compass, are porro prism binocs.


What I have found with the 8x32s is that they are light and they are OK. They do not have the eye relief of the 7x50s, or the exit pupil. While exit pupil is ordinarily discussed in the context of night use, it also affects the degree to which accurate alignment between the eyes and the binocs is necessary. Therefore 7x50s, with an extraordinarily large exit pupil and long eye relief, are forgiving of placement on the face allowing them to be quickly and easily used and pointed in a way that the 8x32s can not. They do not have a compass.


I find that they are useful, during the day, for things like determining whether a vessel is anchored or drifting, whether a boat has fishing lines out, whether a drifting boat has mechanical problems, whether a boat has swimmers in the water, etc. I like having them on the boat. I use them. They're convenient.


Unlike the Polaris they are not going the help you read the number on a backlit buoy or daymark at dusk. They are not going to help you figure out, at night, that the light near shore 3 miles away is the sternlight of a fishing boat that has two people on it and has a red nav light visible but partially obscured by emergent vegetation.



The 7x30 porro prisim binocs you are considering will be somewhat heavier and bulkier than pentaprism 8x32s. The compass versions would add some additional bulk. I would assume better optical quality but am unsure how eye relief and field of view would be affected.