Does higher power demand fancier optics? (1 Viewer)

Just tossing this out:

In gearing up for a quality 10x view and I've noticed this
in my samplings: that for older long-style porros, relative sharpness
for 10x can be quite good, but for recent (short) roofs and porros,
there is a softness that creeps into the resolution unless you
pay a pantload more. I'm not setting down a rule, just observing
a trend in my travels and acqusitions. It seems like you could get
a very impressive 8x30/32 now under $200 but the 10x42 would be
a bit lacking without a few hundred more, or going to an old long-barreled
10x50. I'm less concerned with porro vs. roof these days and more
concerned with the way 10-12x seems to tax the short-barreled sharpness.
The same model in a 10x often doesn't play out as crisp as the 8x.



Observations?

Optics Nut,

Bingo! That's why I've always preferred 10x50s over 10x42s. I've made the same observations myself and posted them on the forums. I don't remember if there was a technical explanation for this or if the experts denied it was true (a 10x is a 10x is a 10x), and certainly, I haven't tried all the 10x bins out there, but from my sample group, the cheaper 10x bins seemed lacking, and generally, porros beat roofs in the 10x42 configuration. Roofs have improved so the gap isn't as wide as it used to be.

I also remember Stephen Ingraham posted on Better View Desired that he tested the 10x42 Swift Ultralite and found the resolution was no better than the 8x42 model! Seemed that way to me, too, having tried both of them and having owned the 8x model (and 8x ED model) even though I just did an eyeball test.

In any case, if you're going to sell the farm to buy a high end 10x bin, you needn't look further than the Swaro 10x42 SLC-HD (original). I could see myself using the 10x SLC-HD for when I'm out and about. The extra reach, and larger image is nice to have when looking at birds at medium to long distances, and heck, even at closer distances.

I was sitting in the backyard last week on one of the two benches near the tube feeder, and I watched birds at my suet feeder, which was only about 10 ft. away. They're used to me and are not bothered by my presence or those funny looking big eyes I put on (bins). The detail I could see was so much better than what it is when I'm sitting on the other side of the yard about 40 ft. away. I thought, this is the way I want to see birds - close up and personal.

My backyard is thickly wooded, in fact, after all the rain we had, "it's a jungle out there, disorder and confusion everywhere, no one seems to care, well I do, hey, who’s in charge here?" The thick canopy blocks a lot of light, so having 42mm aperture is also helpful.

Image-wise, I think the 10x42 SLC-HD is just about perfect -- high resolution, great edges, snappy colors and contrast, low distortion, and heavy enough to keep those bad vibrations from a-happenin'. If I sold all my bins and telescope, I could afford one. But I'm reluctant to put all my eggs in one basket, particularly in a 10x model, which might be hard to sell later if I needed the eggs.

Also, with Swaro focusers, yer pays yer money and yer takes yer chances. You might get a good 'en, you might get a coarse 'en, or one that's noticeably harder to turn in one direction, which might or might not bug you. So if you can visit a store that has more than one sample (if you can find a store that still carries the original version), try several and pick the one with the smoothest focuser.

Just Plain Nuts

Aha....I'm on to something, then. There's a history.

I noticed, at the mid-low range, the Vortex 10x50 Diamondbacks and the Nikon Prostaff 10x50s
are both disproportionately long....and they both have top raves. Stretch roofs, as it were.

I think the trouble comes when they slap a 10x eyepiece on an 8x42 chassis.
I'll bet a long-bore 10x42 would be OK.

The first roof 10x42 I tried, I realized: you have a lot of homework and dodging to do to get to a decent 10x.
Gold falls into your lap at 7x and 8x. At 10x, you're:

---shaking more (I've got the brows/frontmost-grip trick for that)
---dimmer (or you're getting bigger)
---relatively fuzzier (or you should be getting longer)
---have a shallower depth of field (unless you look far away)
---more sensitive to outer lens surfacgunk (unless you boost your exit pupil...another point for 10x50)

If I did roofs, I would go for 10x50 and be sure the length was relatively longer.
That seems to save lots. Of course, there isn't too much difference between
10x50 porro and 10x50 roof at that point,
so I'll just savor my 10x50 Selsis another year. They are actually quite light for the size.

So why do 10x? Other than distance,
for those little details on the little critters, of course. Less work to see the finer details.

Any really long 10x42s?
Ah.....yes, the 10x42 Nikon ProStaffs ... very long-nosed.

Eagle Optics will have some demo Kowa Genesis 10.5X44 at $729 in a couple of weeks if that is of any interest. The Opticron HRWP 10X42 has "Alpha" level optics at a distinctly non Alpha price, but I don't know how available they are in the USA. My BD10X44BP Poro has a narrow FOV, but the view is astounding, and with 3D to boot. A lightweight monopod might be a good way to get rid of the 10X shakes, not to be confused with the hipi hipi shakes. :-O

OPTIC_NUT said:

Just tossing this out:

In gearing up for a quality 10x view and I've noticed this
in my samplings: that for older long-style porros, relative sharpness
for 10x can be quite good, but for recent (short) roofs and porros,
there is a softness that creeps into the resolution unless you
pay a pantload more. I'm not setting down a rule, just observing
a trend in my travels and acqusitions. It seems like you could get
a very impressive 8x30/32 now under $200 but the 10x42 would be
a bit lacking without a few hundred more, or going to an old long-barreled
10x50. I'm less concerned with porro vs. roof these days and more
concerned with the way 10-12x seems to tax the short-barreled sharpness.
The same model in a 10x often doesn't play out as crisp as the 8x.



Observations?

Click to expand...

I'm confused. What do you mean by "long" 42mm binoculars. Are you talking about 42mm binoculars with the standard F4 objectives as long or do you mean shorter ones which have been "tweaked" when you talk about shorter 42mm binoculars? To clarify; what is the focal length of the 8x42 chassis you mention in the 3rd sentence of thread #3?

Bob

OPTIC_NUT said:

Aha....I'm on to something, then. There's a history.

I noticed, at the mid-low range, the Vortex 10x50 Diamondbacks and the Nikon Prostaff 10x50s
are both disproportionately long....and they both have top raves. Stretch roofs, as it were.

I think the trouble comes when they slap a 10x eyepiece on an 8x42 chassis.
I'll bet a long-bore 10x42 would be OK.

The first roof 10x42 I tried, I realized: you have a lot of homework and dodging to do to get to a decent 10x.
Gold falls into your lap at 7x and 8x. At 10x, you're:

---shaking more (I've got the brows/frontmost-grip trick for that)
---dimmer (or you're getting bigger)
---relatively fuzzier (or you should be getting longer)
---have a shallower depth of field (unless you look far away)
---more sensitive to outer lens surfacgunk (unless you boost your exit pupil...another point for 10x50)

If I did roofs, I would go for 10x50 and be sure the length was relatively longer.
That seems to save lots. Of course, there isn't too much difference between
10x50 porro and 10x50 roof at that point,
so I'll just savor my 10x50 Selsis another year. They are actually quite light for the size.

So why do 10x? Other than distance,
for those little details on the little critters, of course. Less work to see the finer details.

Any really long 10x42s?
Ah.....yes, the 10x42 Nikon ProStaffs ... very long-nosed.

Click to expand...

Actually, at higher power the optical design turns easier: Smaller angle of view means less field curvature, Coma and Astigmatism. High power eyepieces are often simpler than their low-power counterparts.

But things are not that simple: The prism always degenerates image quality, and this turns visible at high power. Such effects should be particularly serious with low-cost roof prisms. Then, mechanical alignment issues become visible at higher powers. The manufacturer doesn't waste money, he does it accurate enough so that the blur due to misalignments remains just invisible. At high power, tighter tolerances are needed, but they are using the same mechanical setup for the entire product line from 7x to 12x.

Roof binoculars with internal focusing are facing the problem of the floating focusing lens. The binocular can be perfectly sharp only at one particular setting of this lens, all other distances are compromised. If you want a short close-focusing distance, the problems increase. Not to mention that moving elements are always a potential source of trouble. All these effects are causing a certain amount of blur, which becomes visible at high power.

The best way to go with high power binoculars: Long focal ratios (lens-radii turn larger then, curvatures decrease, tolerances against misalignment increase), and Porros (far more fault-tolerant than roofs).

Cheers,
Holger

The best way to go with high power binoculars: Long focal ratios (lens-radii turn larger then, curvatures decrease, tolerances against misalignment increase), and Porros (far more fault-tolerant than roofs).

Click to expand...

And of course, the objective and field lens keep more to the thin-section approximations this
whole ball of wax rests on. Perhaps more aspherics will come to the rescue at hi-power.

Long AND porro, then. My 10x50 Selsis seem to bear that out...I could shave on the edges
at 100 yds and they weren't tip-top, just 'better grade'.

I'm confused. What do you mean by "long" 42mm binoculars. Are you talking about 42mm binoculars with the standard F4 objectives as long or do you mean shorter ones which have been "tweaked" when you talk about shorter 42mm binoculars? To clarify; what is the focal length of the 8x42 chassis you mention in the 3rd sentence of thread #3?

Click to expand...

I am not getting precise about internal objective focal length, Caesar...just observing the chassis.
Lord knows, finding the precise number is more trouble than I care to go through.
It looks like 6.8"(the N.Prostaff 7) is on the way-long side, and most are around 6 inches
...the Viper is 5.8", but it costs a lot more
..the Zeiss Terra is interesting: 5.5 inches ......But: it has a special prism!

I don't think the trouble with a short barrel is insurmountable...I just think it can
be expensive to keep it sharp, eat more and special lenses, using the Schmidt...whatever prism, etc.
and also prisms with an even higher index than BAK4, to avoid issues there..

But this could just be a small piece of the bigger picture: the driver for roofs has always been size,
and getting over the issues costs. I think at lower powers the roof 'price penalty' has dropped a
lot recently. Perhaps higher power is a still challenge area. Going long has its cost, of course:
it's harder to get fov without really chunky prisms...and we're back under size pressure again,
width vs. length.

My Selsi 10x50s are 6" long, but then you have to add 2" for the 'porro shuffle'.
I'm calling the glass-phase-length about the same for either design because
it would be a lot of demolition cost to find that figure. ;-)

Fascinating solution on the Zeiss Terras...they made it down to 5.5" though!

That was very depressing Holger.|=(| :-O

Holger Merlitz said:

Actually, at higher power the optical design turns easier: Smaller angle of view means less field curvature, Coma and Astigmatism. High power eyepieces are often simpler than their low-power counterparts.

But things are not that simple: The prism always degenerates image quality, and this turns visible at high power. Such effects should be particularly serious with low-cost roof prisms. Then, mechanical alignment issues become visible at higher powers. The manufacturer doesn't waste money, he does it accurate enough so that the blur due to misalignments remains just invisible. At high power, tighter tolerances are needed, but they are using the same mechanical setup for the entire product line from 7x to 12x.

Roof binoculars with internal focusing are facing the problem of the floating focusing lens. The binocular can be perfectly sharp only at one particular setting of this lens, all other distances are compromised. If you want a short close-focusing distance, the problems increase. Not to mention that moving elements are always a potential source of trouble. All these effects are causing a certain amount of blur, which becomes visible at high power.

The best way to go with high power binoculars: Long focal ratios (lens-radii turn larger then, curvatures decrease, tolerances against misalignment increase), and Porros (far more fault-tolerant than roofs).

Cheers,
Holger

Click to expand...

That was very depressing Holger.

Click to expand...

Hah...said Pooh Bear to Eeyore..

The advice is true, but follow it to Nirvana and you're hauling around foot-long funnels.
;-) Just like the aircraft carriers and yacht club lawns.
It's all trade-offs.

Dunno, but...

I have a pair of Atlas Radian 10x42's that are 5.4 inches long, and very compact, it seems for a 10x (5.0 inches wide). They might not be alphas, but they are darned nice for the money, and sharp enough for my eyes. Also handle very well besides-easy to hold and focus. I got them on sale from Eagle Optics around Christmas, and was pleasantly surprised how good they were. The only shortcomings that I can note are the narrower field of view (305'/1000 yds) and the short eye relief (15.5). Oh, and they aren't porros (no 3D vision). ; ) Even so, they still perform very well for not a lot of moola.

http://www.eagleoptics.com/binoculars/atlas-optics/atlas-optics-radian-10x42-binocular?

Impressive..now I'm wondering what the lens layout is. Not too bad on the FOV.
Keeping FOV down a bit is a critical tactic when pushing other parameters.
All that torment of lenses and prisms Holger is talking about is at the wide ray angles.
The competition out there is incredible. I don't know too many people with binoculars..
maybe the world market is a small percentage with a big closet full of binoculars each.

Thanks to my weird buying habits, I've owned more than one specification in three binocular families, probably enough that I should comment on this, even though be warned that some speculation is coming.

Fujion FMT-SX: 6x30, 8x30, 7x50, 10x50 and 16x70
Zeiss FL: 8x30 and 10x56
Leica: 8x42 BA, 10x50 BR, 12x50 BN (different coatings but unchanged optical design)

Almost without exception, the lower powers have a super crisp snap to the image that fades with increasing magnification. A good 12x seems great without a comparison, but wait till you try the 10x. And then, wait till you see the 8x. I favor high powers, because I see more detail with them, and I would love to report that they are as fine as the low powers, but that is not the case.

As neat an experiment as the above binocular models/series might be hoped to provide, there is still no clearly isolated cause for the effect. Coatings vary within the families, and there is something psychologically attractive about the steadiness of a low power view when the binocular is hand held, but I'll just ignore those things or it becomes hopelessly complicated.

Henry Link has kindly taught us how a large exit pupil can be truncated by a small eye pupil, effectively increasing the focal ratio of the objectives, and bringing optical improvement. He has also presented compelling data, from stopping his 8x56 FL down, to support the point, and I am convinced that his argument is good and practically significant. But other things are coming into play as well, or the 10x56 FL ought to be even snappier than the 8x42, and it is not.

The three low power Fujinons are an interesting case. The 7x50 is particularly stunning to my eyes, although part of that is due to the great viewing comfort with a 7.1 mm exit pupil. Still, the 8x30 and 6x30 are very close to it and to one another on sharpness per se. I have determined (by measuring eyepiece travel as a focus distance is varied) that the 30mm's objectives are close to f/5 however, a large ratio resulting mainly from the long light path through the large prisms. That sounds like Henry's argument coming into play.

But if we combine the three low power Fujinons together into a unit for comparisons, the picture is clear. Low magnifications look sharper. Exit pupil as related to effective f/ is part of it, but something about construction quality that is not simply accounted for by optical theory is also a strong contributor. Regardless of the aperture, or effective aperture, something in there simply does not support high magnification as well as low.

I can't imagine why it should be any harder to adjust a large binocular than a small--the lenses and prisms all mount and move the same way. Of course, the adjustment must be made with proportionally higher accuracy, the higher the power, which may not be realized on the assembly floor.

Color fringing is known to be more apparent at higher power, and the effect would probably be reduced if the higher powered Leicas and Fujinons were given ED objectives. Both FLs, however, do have ED glass, yet the magnification effect is present. This suggests that Zeiss's choice of ED glass may be only marginal, allowing color error to still be a quality limiting aberration.

I suspect it's also something Holger mentioned--the prisms. If the prisms are optically lumpy, high enough magnification is going to show it. I hate prisms, but it's better than everything looking upside down!

Ron

The discussion hasn't taken into consideration that the perception of sharpness is a joint function of image resolution and acutance. As retinal image size increases, acutance (the first derivative of edge contrast) decreases. For this reason, a photograph that appears to be tack-sharp at 12 ft. may look much softer when viewed from only 5 ft. away. By moving closer, the image size increases, but its acutance decreases. As size increases with magnification, acutance also decreases.

Ed

ronh: Holger was also referring specifically to the lenses, not just prisms, and the trouble with
both was tied to the severity of the angles...or to put it another way, the f-ratio of the instrument.
I do seem to get sharper views from a physically long 10x than a short one, but that's at the same price
range.

But I do agree there is something or some combination of things that somehow makes a higher power
not as sharp as you'd expect. And...I understand using the higher power, anyway. It just makes it
a lot easier to look at more detail. We wouldn't be using magnifiers at all if true perceived details
was better at 1x. Instead of shifting towards 10-12x, I find two tracks are developing: ~6x and ~10x.
Depth of field is crucial when the critters bet busy and the foliage closes in, so it's 6x for woods
and 10x for fields clearings and ponds.

I can't imagine why it should be any harder to adjust a large binocular than a small

Click to expand...

I'm not sure if this in reply to someone else, but I'm always talking about maximum possible resolution,
not having a hard time finding it. There is an interference in a street sign 70 yds away that makes
trimming the focus incredibly precise. The bands get very clean at 6x or 7x, which suggests there is
some absolute resolution getting better. Of course, that doesn't matter when the eye cannot see
that fine without slowing down. So 10x will always give more detail in a practical sense.

a large ratio resulting mainly from the long light path through the large prisms. That sounds like Henry's argument coming into play.

Click to expand...

And into Holger's theory, for both prisms and lenses. Optical engineering relies on the "thin lens approximation",
at least for modern spherically-ground lenses. The distortions get awful very quickly. Prisms, especially roof,
usually sail a lot closer to the wind. It's no accident a lot of super-resolution instruments have less FOV..
...you can achieve so much more at less fov for edge-focus fanatics.

elkub:

As retinal image size increases, acutance (the first derivative of edge contrast) decreases.

Click to expand...

I think there is something to that, and maybe my/our 'feeling of sharpness' could be denying something
as simple as that. Here is another factor as well, speaking of edge detection: when I sharpen a picture,
I always downsample it, sharpen, and upsample again. That prevent noise and jitter from turning a
a sharpening into a raggedy effect. So let's say the optic cortex works that way: at a lower power,
the 'clues' to where the edge is are much more consistent and the mind can sharpen much more easily.
This, combined with the retinal effect you mention, might give us a much higher 'preceived' sharpness.
I say perceived because it may or may not be the real edge, just an easier edge to get straight.
When I look through the old hand-ground flouride/bak4 6x30s, I sometimes see a weird 3D effect
where things 'pop' out 150 or so yards away. That makes little sense, unless it's similar to my
over-sharpening of photos. It correlates with a darker background.
There is something special going on, though. The edges in the (2-degree..heh) view of my
7x35 Galileans are incredibly sharp, but the brightness is extreme as well.

bh:

Eagle Optics will have some demo Kowa Genesis 10.5X44 at $729 in a couple of weeks if that is of any interest. The Opticron HRWP 10X42 has "Alpha" level optics at a distinctly non Alpha price, ...

Click to expand...

I hope to have some Meopta 6.5x32 'Alpha-Slayers' arriving soon. They hit the beach at $300, although that
might have been a teaser. Still, the Vanguards and others seem to be making great 8x gains circa $200.
The refreshed Diamondsbacks are incredible.
If the breakthrough price is $729 at 10x, there may still be some time to go before the 10x dragons
are slain 'affordably'. Machines are just starting to produce asperical surfaces in quantity....so who
knows? Element count make creep up in oculars, too, although that adds substantial weight and width.

Ed,

Thanks for pointing that out. Please correct me if this is wrong:

I believe the origin of actuance must lie in the pixelation of retina. So as a blurred edge is increasingly magnified, the blur spreads over more pixels, and looks blurrier.

A naive interpretation (something I'm good at) predicts that the effect would occur whenever the magnified blur exceeded the eye's resolution of about 1 arc minute, corresponding to retinal cell spacing. A good 40mm binocular will resolve 3 arc seconds, so it might seem from that, that one would not notice actuance blur up to 20x.

But, the marginal visiblity of something small, like the visibilty of edge blur, occurs at smaller angles than required for the resolution of two objects. For example, the Cassini division in Saturn's ring is frequently seen at magnifications where its size is considerably less than what the eye can "resolve'. Unfortunately I don't "know the numbers" on these effects, but I suspect that actuance explains why low power binoculars look sharper. I will do some homework. If the visiblily threshold is al small as a third or a half of the resolution threshold, we are there.

Ron

I'd use '50s all the time if they weren't so big. But if that's not a concern for you, then you might as well keep using the Selsi's. All you'd gain from a modern 10x50 porro might be better coatings. About that long-bodied Prostaff 7 that you mentioned, my suspicion about the old P7 is that the front element is actually an optical window (or at the very least a very weak positive lens group), and the actual "objective" is the floating lens group behind the front element. If I'm correct then the physically long barrels of the P7 aren't really indicative of the objectives having a slower-than-usual focal ratio. But either way, if you're interested in roofs with extra long barrels, then you might also consider the Kowa SV series as well as the Carson XM-HD series. If the specs sort of resemble the P7's, well, maybe there's a reason for that!

peatmoss said:

I'd use '50s all the time if they weren't so big. But if that's not a concern for you, then you might as well keep using the Selsi's. All you'd gain from a modern 10x50 porro might be better coatings. About that long-bodied Prostaff 7 that you mentioned, my suspicion about the old P7 is that the front element is actually an optical window (or at the very least a very weak positive lens group), and the actual "objective" is the floating lens group behind the front element. If I'm correct then the physically long barrels of the P7 aren't really indicative of the objectives having a slower-than-usual focal ratio. But either way, if you're interested in roofs with extra long barrels, then you might also consider the Kowa SV series as well as the Carson XM-HD series. If the specs sort of resemble the P7's, well, maybe there's a reason for that!

Click to expand...

The Prostaff 7 does have a flat protective glass element for water proofing
as the final lens. The construction of this binocular seems similar to the
Zeiss BGAT classic style with the moving objective near the end of the
barrel. However the Zeiss is open without a protective lens, to make
them waterproof.

One nice thing about this construction, is the length does give the binocular
a bit more hood out front to help with glare, flare and light coming in.

I have not seen how the new Nikon Prostaff S "short" models are constructed, and they may have a more typical design with internal focusing lenses with a conventional curved objective lens.

I suppose that does count in how the focal ratio is calculated.

Jerry

How much of the less sharp image in the higher magnification can be attributed to the impurities in the atmosphere also being magnified ? On a day when 8X looks acceptable, haze and mirage make the 15X Kaibab almost unusable.
Give the Kaibab some good air, and while not quite as bright and sharp as a good 8 or 10X, it is still amazing. We obsess a lot about optical properties, but the atmosphere is seldom ever perfectly clean.

I just realized: A front window with moving objectives is the same surface-count as no window
and a midway focuser lens. I'm not sure on the theory behind Holger's dislike of the focuser lens.
I didn't like them at first, then I realized they don't affect depth of field negatively, and now Holger's
concern. I think it has to do with the steepness of the angle into the focuser and its position.
By it's nature it's supposed to move a little and change the focal point a lot. It is relatively
low power, though...my hunch is that it's a wash, or maybe they can fiddle with it to help
other things. Binoculars are mostly a pile of lenses pittting their distortions against each other,
after all. Otherwise we'd need only two lenses.

Thanks for the model recommendations, Peatmoss! I'll check them out. I love the Carsons I got,
just 8x32 VPs I made a solid hood for, but they are very nice. Stepping up the price for 10x is something
I'm pondering long-term.