which pair? (1 Viewer)

I agree with everything Alexis has said. The often cited figure of 1 arc minute for human eyesight acuity is actually calculated in a different way from the way telescope resolving power is usually measured. The familar Snellen chart of eyesight acuity measures the separation angle between lines. Telescope resolution (when it's measured on a line pair chart like the USAF 1951 test pattern) is usually based on the angular width of line pairs (one line and one space), which is twice the separation angle between the lines, so 1 arc minute of eyesight acuity on the Snellen chart corresponds to 2 arc minutes of telescope resolution on the USAF chart. A few years ago Kimmo Absetz posted an excellent explanation of this subject.

Of course, either separation angle or line pairs can be used to express resolving power as long as the notation is consistent. Both Jan Meijerink and Kimmo Absetz have chosen to use separation angle for their measurements of telescope resolution. Misunderstandings occur when the reader doesn't know which one is being used or if the two are mixed as in Kevin's post above.

Here is the basis for my comment "The real optical difference is that an 8x Promaster will show a touch more detail "way-out there" than a 10x Viper.

When I first got the Promaster, I used it deer hunting. Here's the scenario; A cold, rainy, gloomy day. We spotted a group of deer in some gray brush. Had a laser range finder, but there was not a reflective enough target to accurately range the distance. However, it was at least 850 yards. There were five pairs of eyes, and we ALL saw the same thing. There was one small buck in this group of deer. The 8x Promaster was able to show us the small antlers, not any real details of them, just that they were there. The 10x Viper was not able to show those antlers. ALL of us thought the Promaster image was brighter, clearer and sharper than the Viper. We ALL thought the Viper image was bigger, but not as clear. Now I apologize for attributing this difference to resolution.

But Alexis, don't tell me you don't believe it or that I am imagining things. I'm not so stupid as to stand up here in front of the world, including a bunch of people who know a lot more about optics than I do (likely including you), and shoot off silly claims. One of the pairs of eyes in the group was a State Trooper who works a lot in wildlife violation investigation, and has some on the job requirements of being able to accurately report what he sees. The trooper also had a Swarovski 8.5 EL. It also showed the small antlers where the Viper didn't. Want to talk about how far you can read something like the black lettering on a yellow road sign, fine, the Viper will read further. There were other things we ALL saw that were similar in nature to the small antlers on the little buck. If that is not resolution fine. What is it? If I need to educate myself on proper terminology use I will.

I also make no claim to have either a bad Viper or a cherry Promaster. They are each my sample of one. The Viper is probably going up for sale, because that difference (whatever it is) seems to be a permanent, repeatable feature between the two binoculars.

SteveC's post shows what happens when you use 100% (black/white) line pairs for measuring resolution and the comparing bins rather than measuring the MTF to determine the contrast level at a given "resolution" (spatial frequency).

It's quite possible for Steve's Promaster's to have an better MTF (due to its better contrast) which allows the "resolution" of his 8x bin on a given low contrast target to exceed that of the 10x bin on the same low contrast target.

On the MTF plot the contrast level of the Promaster at the low frequency end would exceed the Viper. As the spatial frequency is increased both would decrease to zero. The two curves would eventually cross (at the spatial frequency they have equivalent performance).

The 8x bin MTF would cross the spatial frequency axis (i.e. contrast difference is zero) before the 10x bin MTF has hit zero showing it's limiting resolution would be worse the higher magnification bin.

The 10x bin (+ the eye) would exceed the 8x bin in resolution against a black and white target (or against two separated points of light on a black background). But against a real life low contrast target that isn't always true.

Plus there may be other effects (CA, stray color and other aberrations) that cause the Viper to have lower contrast on this target than the Promaster.

MTF measurements give you more data than "in the limit" data you get from a simple resolution chart measurements.

Kevin,

Real MTF plots of these binoculars would be very interesting to see, but we can't tell much from imaginary ones. If they look like your description then the Viper has serious problems from excessive aberrations or defects. The actual contrast level of the target doesn't really matter. That's always 1 on an MTF diagram. If the Viper can't show more detail than the Promaster on any target, high contrast or low, with a 25% magnification advantage then something is seriously wrong with it.

I don't doubt Steve and his friends' experience with the antlers, but that's is not a very well controlled test. It's more like an observation with an unexpected outcome that needs to be investigated with a controlled test.

Henry

henry link said:

If the Viper can't show more detail than the Promaster on any target, high contrast or low, with a 25% magnification advantage then something is seriously wrong with it.

I don't doubt Steve and his friends' experience with the antlers, but that's is not a very well controlled test. It's more like an observation with an unexpected outcome that needs to be investigated with a controlled test.

Henry

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Henry,

I really wonder about controlled tests. I am a biologist, not an optical engineer, but I realize the necessity for creating controled tests, with repeatable results. Not much except for arguement would result without these controlled tests. I do wonder how far one can sometimes go with them. It seems to me that when somebody goes out the door with their binoculars they are headed off into a series uncontrolled tests, or as you put it above, observations with possible unexpected outcomes.

You are right, my observation is not a very well controlled test. It was my intent only to register it as an observation. Wildlife typically does not appear next to a resolution chart with a set of matched line pairs. I'd like to see somebody develop a resolution chart or charts, that could be used at varying distances out to several hundred meters. Maybe they're out there, but I have never seen any.

Now for the past some time, I have put the Promaster and the Viper to an amateur's version of a resolution test. What I used is a multi colored chart posted by Surveyor on another thread some time ago. In this case, the Viper does indeed show more detail as far out as either binocular can read the largest items on the chart. The Promaster image seems brighter and clearer, and it is easier to read the last size level that it can read, but will not read as small a level as the Viper. I don't doubt that is a repeatable result. From what I can see from over a year's experience with that Viper, I don't think there is anything seriously wrong with it. Take both binoculars clear out to Jupiter and the Viper has a clearly larger planet image, but the edges of the planet are sharper and more clearly defined in the Promaster. The moons are easier to see with the Viper.

Put the Promaster against my 8x42 Nikon Monarch, then the Monarch pretty well comes out in second place, they wouldn't put the antlers on that little buck either. Neither would an 8x30 Yosemite. Nobody would have said the 10x Viper didn't show more detail than those 8x glasses. Same deal with the Swift 7x36 Eaglet.

Now as a strictly amateur observation, it has always seemed to me that the repeatable optics tests are weighed in favor of higher magnification. In close, what else can be expected other than a decent 10x will best an 8x. Now, out at the distance where we were looking at those deer, the Viper image was indeed bigger, but it was also not as clear. On a clear bright day, the Viper does in fact seem to show a bit more detail, but again its image is not as sharp as the Promaster.

With some trepidation I now press the submit button.

In this case, the Viper does indeed show more detail as far out as either binocular can read the largest items on the chart. The Promaster image seems brighter and clearer, and it is easier to read the last size level that it can read, but will not read as small a level as the Viper.

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This is my experience with 10x vs. 8x as well. And my 8x porros give the appearance of an easy to focus image, on the smallest fonts of text I can read. The 10x is clearly not as natural and the depth of field is less.

Anyone can play with a scope with a zoom lens and compare two magnifications. The smaller magnification on the same zoom lens always looks brighter, better contrast, easy to focus. If you try the extreme ends of your zoom, the smallest end looks beautiful compared to the largest, which by comparison looks like mud. Even the color may look off. In zooms with less XX range, it is less obvious. My first scope did that , 20-60x. It was only good up to 45x.

HAs anyone tried Hawke and Promaster in 10x42 format?

Steve C said:

In this case, the [10x] Viper does indeed show more detail as far out as either binocular can read the largest items on the chart. The [8x] Promaster image seems brighter and clearer, and it is easier to read the last size level that it can read, but will not read as small a level as the Viper.

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Tero said:

This is my experience with 10x vs. 8x as well. And my 8x porros give the appearance of an easy to focus image, on the smallest fonts of text I can read. The 10x is clearly not as natural and the depth of field is less.

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I wonder Steve. Might the advantages you saw in the Promaster over the Viper be attributable to the fact that you were comparing an 8x to a 10x? Perhaps we really need an 8x vs. 8x comparison to have a solid basis for declaring whether one is optically superior to the other?

Best,
Jim

Steve,

I read back over your posts in this thread. The antler story seems to be a single anomaly, contrary to your other tests comparing details visible at 8x vs 10x. If you are curious enough about it, maybe you could simulate the same lighting conditions with your resolution target or download and print a USAF 1951 chart (accurate size wouldn't matter). I would also suggest using a tripod. I know I can't hand hold even 8x binoculars steady enough to see the smallest details in the image.

Henry

Steve C;

First, I completely agree with Alexis and Henry, resolution is resolution is…., and is both measurable and repeatable. It is also linear and consistent with distance, being an angle.

A couple of opinions and not at all substantiated. I assume you are comparing 8x42 to 10x42. If so the 8x is about 56% brighter than the 10’s, which may let you recognize details or patterns quicker, but only details that are there. It will not show the details of the 10x. I think of this like a photographer would use a fill flash. Just a better illumination of what is there.

Next the 8x will show less shake and that may also aid in recognition of patterns or details quicker, but again, it will not create the detail of increased magnification. We have all seen the dramatic ease of identifying/recognizing patterns/details with a stabilized or tripod mounted bino versus handheld.

I guess I equate quick recognition with what others describe as a relaxed view and at my age and eyesight, I tend towards 7x and 6x binos far more often than 10x. My favorite general-purpose configuration is 7x42.

That said, I do not think I have ever seen as dramatic a difference between 8x and 10x as you describe and I think the difference in magnification would over ride the brightness advantage of the 8’s. When, as Henry put it, I have an observation with a very unexpected result, then I will start testing. In this case the first thing I would check would be collimation. The 10x needs to be collimated 25% better than the 8x for equivalent performance. Believe me, binos do not need to be close to the rejection limit for a degradation of the view to be apparent. Collimation is the most common problem I find with less than ideal views.

Have a good day.

Ron

Steve,

To simulate the "antler" scenario, you might consider the "Graveyard test". It is a simple way to compare resolution, contrast, low light, stray light, off-axis sharpness, etc. (and perhaps more importantly, the combined effects) at distance, and on different targets. It will not give you a very technical result, but might help you sort out the differences between the different models.

APS

APS: Can you describe the "Graveyard test"?

Kevin Purcell said:

APS: Can you describe the "Graveyard test"?

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Sounds like a dead scary way of finding out your bins suffer from ghosting...

Henry and Surveyor,

Thanks for your input. I was/am apparrently using too broad a definition of resolution. Everything seems to point to the technical definition of resolution as relating the ability to sort detail on the basis of line pairs and detail from charts. I can get that. Testable and repeatable. So I suppose we as individual users, are left to sort out from the total image all of the aspects that ultimately contribute to the totality of the image we observe as to what we like best. I was lumping that overall image quality as "resolution". The overall I like that one better than thais one is therefore subjective, not testable and repeatable. If it isn't resolution, there is certainly something a lot more "appealing" in the image of the Promaster.

Jim,

Just sold my 8x Viper because I have the 8x Promaster, so if I was not clear on my Promaster vs Viper comments those were 8x to 8x comparisons, except for the antler episode, where the 8x Viper was not there. The Nikon Monarch 8x42 is going up for sale, but I may not be able to get enough for it to convince me to sell it. I did have another 8x Viper which I did return for the 10x I have, but some months later bought another one, which I gave a good deal on to a friend who needed a good glass.

APS,

Another request for a description of the graveyard test. Please tell me it is not what Norm thinks .

Steve C said:

APS,

Another request for a description of the graveyard test. Please tell me it is not what Norm thinks .

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"Sounds like a dead scary way of finding out your bins suffer from ghosting..."(normjackson)


The "Graveyard Test" is best performed on October 31st, near mid-night ...

Okay, okay, it's not so scary (although it might be for some). Actually, it's just a convinient use of the many, many targets with written inscriptions, for comparing what I think of as "distinguishability" between bins. First, find a suitable cemetary, preferrably with long views. Then simply find a good vantage point at the desired time for lighting tests, and start picking targets. With binocular "A", try to find a headstone on which you can not quite make out the name, etc. Then, attempt to do so with "B", and so on. Then, switch the order. Since there are almost limitless targets, one can repeat the process over and over until you determine the "winner". I also find that it's a good way to evaluate the "extra time" that you can get out of larger objectives as darkness sets in.

So far, I haven't encountered any ghost images; but blackouts do send chills down my spine. And hooooo knows, you might see an owl or two, or some vampire bats ...

Good luck (if you dare), APS

APSmith said:

"The "Graveyard Test" is best performed on October 31st, near mid-night ...

Good luck (if you dare), APS

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Suppose one does the Graveyard Test next Friday night (31st Oct.), and focuses on an old, moss-covered headstone at about 70 metres, and can only dimly make out the letters until they resolve themselves with a bit of fine-focussing until one can make out....ONE´S OWN NAME!:eek!:

Sancho, with today's economy, a graveyard plot is as good an investment as anything. But I would leave the carving of the name on the headstone till the actual event.

Good idea, Tero!

I believe Tolstoy wrote a short story about this subject. I think it was entitled "All the Land a Man Needs," or something like that.

Bob

ceasar said:

Good idea, Tero!

I believe Tolstoy wrote a short story about this subject. I think it was entitled "All the Land a Man Needs," or something like that.

Bob

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Too true! Here it is! http://www.katinkahesselink.net/other/tolstoy.html

What about LW, the OP? What did you choose in the end?

Steve C said:

Henry,

I really wonder about controlled tests. I am a biologist, not an optical engineer, but I realize the necessity for creating controled tests, with repeatable results. Not much except for arguement would result without these controlled tests. I do wonder how far one can sometimes go with them. It seems to me that when somebody goes out the door with their binoculars they are headed off into a series uncontrolled tests, or as you put it above, observations with possible unexpected outcomes.
.

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Me too.
Recently I was viewing some bins at a large Sporting Goods store and all the way across the store on the far wall they had this "binocular test center" poster made by Bushnell and it was a series of black and white lines, an "eye chart" a black and white drawing, etc. Looking at this with different bins was of no use to me.

Instead, I viewed the mounted Pheasant they had on the shelf next to it.
For me, it makes more difference in how much feather detail and brightness I noticed between different bins.