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Help resolving potential issue with UV 8x42HD+

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Old Monday 19th August 2019, 02:15   #1
Moose8
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Question Help resolving potential issue with UV 8x42HD+

Hello, I'm a new owner of a demo model UV 8x42HD+. I was comparing it to my old UV8x32HD. I sat out with them for the first time early this evening through 1 hour before and past sunset here. I have two concerns after observing and comparing the 8x42's to my older 8x32s.

First, I really wasn't able to notice a significant difference in low light performance between the 42's and the 32's. I kind of think maybe the 42's were a touch brighter but honestly it was within the margin of error of maybe being just in my head. Even holding one barrel of each binocular to each eye simultaneously to view an early evening star, the ambient background sky light seemed indistinguishable in each eye. Detail in dark forested shadows also seemed negligible. I'm 35 and have no issues with my sight or night vision that I'm aware of. Is the difference between 32 and 42 (and HD and HD+ at that!) supposed to be this subtle?

The second issue is that earlier in the evening I was viewing a backlit woods, with the sun having set behind the trees. The view through my older 8x32's was OK, but in 8x42's there was significant glare or flare (not sure of the correct term, rings of light near the edge of the image). Are larger objective lenses prone to more flare? I didn't encounter this issue using the 42's in standard daytime terrestrial viewing elsewhere, but it was a big problem viewing my garden in the evening!

I guess I'm asking if these are problems with my 8x42 binocular or problems with me just getting used to an 8x42 format up from my 8x32. I was rather hoping for a bit better low light performance.
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Old Monday 19th August 2019, 12:13   #2
Binastro
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Hi Moose8,

Have you actually measured your pupil size in twilight?
If you have a dark sky, see if you can see slightly fainter stars in the 8x42 compared with the 8x32.
Give yourself twenty minutes to get dark adapted.

Some people cannot easily tell the difference in star brightness, although I can with a 10% or 0.1 magnitude difference.

The problem of glare is to do with the binocular.
It may be that the 8x32 is well designed and well baffled and the 8x42 is not so good.

My early Monarch HG 8x42 is terrible regarding flare and glare, so I use a Leica 8x32 BA, which is very good, especially if a street light is in the field.

Give it time, but it may be that the 8x42 is more prone to glare than the 8x32.

If you use one barrel of each then swap eyes as each eye has a different sensitivity.

The focal length of the eyepieces of the 8x42 will be longer than with the 8x32.
So the eye relief of the 8x42 eyepieces is likely to be greater.
This may mean that your eye is shielding the view with the 8x32 but not with the 8x42.

I enjoyed my visit to the Harvard observatory in Boston.

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B.

Last edited by Binastro : Monday 19th August 2019 at 12:23.
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Old Monday 19th August 2019, 13:09   #3
jring
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Hi,

regarding the bright ring at the edge of the field with a backlit object - you're not the only one to notice it, although this reviewer was not very concerned about it... See the point Flare suppression in this link:

http://www.greatestbinoculars.com/al...x42hdplus.html

This is probably a matter of not so great baffling and will probably stay that way for other examples of this model.

As for perceived image brightness at dusk - it seems you were trying to look into the woods when it was well past sundown - it might have been just too dark for both instruments to show a clear difference. Maybe try to observe with the 32mm pair into the woods at dusk until you notice the image is getting a bit dark and then try the 42mm pair. The difference between a 32mm and 42mm pair for terrestial observation is usually 10 or 15 minutes at dusk or down.

When you tried to observe Venus, I guess the sky was still quite bright in both instruments - probably due to time of day and year (not really late at night and still quite close to solstice) and location (assuming Boston to be not really a designated dark sky area ;-)

Joachim
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Old Monday 19th August 2019, 13:16   #4
Moose8
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Quote:
Originally Posted by Binastro View Post
Hi Moose8,
Have you actually measured your pupil size in twilight?
If you have a dark sky, see if you can see slightly fainter stars in the 8x42 compared with the 8x32.
Give yourself twenty minutes to get dark adapted.
I spent some more time with them last night, but the moon was relatively bright. I spent some time looking at trees in the distance under ambient moonlight (though the moon was behind the house and not in actual view). I could actually make out a lot with both binoculars from just this ambient light, and ultimately determined that the 42mm was marginally brighter than the 32, but boy is the difference subtle. Same with viewing stars. I guess I had just assumed that the jump from 32 to 42 would have been more apparent.

Being relatively young I would have thought my pupil dilation wouldn't be an issue yet, but I wish there was an objective way to measure my actual pupil dilation, beyond my subjective interpretation of brightness. Like, when they dilate your pupils at the optomitrist to their fullest extent, could that be accurately measured somehow? Could that be done at home?

The 8x42's are a used demo pair. I guess I want to determine if it really is just me subjectively not seeing much of a difference, vs the unlikely chance that I purchased something like a lieca factory second that might not have as good light transmission levels, though I've never heard of anything like that happening.

Quote:
Originally Posted by Binastro View Post
The problem of glare is to do with the binocular.
It may be that the 8x32 is well designed and well baffled and the 8x42 is not so good.
I did a bit more reading, and found this article which has a blurb that directly compares the UV 8x42 to the UV 8x32. It says the 8x32 is "overbaffled with truncated exit pupils" compared to the 8x42. I guess this would account for the difference I'm noticing?

Are there objective lens shades that can be purchased for the UV 8x42 that would cut out the glare? It's kind of a viewing edge case where I'm encountering the glare, but the problem is I like to view in the evenings and my whole garden is this back lit edge case!
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Old Monday 19th August 2019, 13:30   #5
Binastro
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Lens hoods may or may not help.
Some binoculars have front threads and camera lens hoods can be screwed in.
At a pinch one could make some from black card.

You could get someone to look at your eyes in dim light next to a ruler.
Or photograph them with a sensitive camera.

Henry has posted more accurate ways.

B.
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Old Monday 19th August 2019, 13:30   #6
jring
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Quote:
Originally Posted by Moose8 View Post
Are there objective lens shades that can be purchased for the UV 8x42 that would cut out the glare? It's kind of a viewing edge case where I'm encountering the glare, but the problem is I like to view in the evenings and my whole garden is this back lit edge case!
Hi,

trying some lens hood is a good idea - maybe first use some cardboard to try if it helps..

Joachim
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Old Monday 19th August 2019, 13:36   #7
Binastro
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I use Imperial and metric drill gauges.
They cost a few pounds each.
They have about 15 holes from say 1mm up. In three rows. I only need the smallest row and a couple from the middle row.
Made in India, from stainless steel, and they seem to have accurate hole sizes.

B.
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Old Monday 19th August 2019, 21:55   #8
tenex
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I normally use the HD+ 10x32 and likewise find any brightness advantage in 42mm models quite hard to detect. I suspect you would have to go to 50 or 56mm to really notice that, as I did.

The UV 42s make some sacrifices for compactness, and the objectives may not be very deeply recessed.

At your age pupil size should be no issue. But do pay attention to the oculars, and ensure the eye relief vs eyecup depth is working well for you. I have trouble with some binos there, including the UV 42 models.
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Old Monday 19th August 2019, 22:34   #9
Moose8
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I normally use the HD+ 10x32 and likewise find any brightness advantage in 42mm models quite hard to detect. I suspect you would have to go to 50 or 56mm to really notice that, as I did.

The UV 42s make some sacrifices for compactness, and the objectives may not be very deeply recessed.

At your age pupil size should be no issue. But do pay attention to the oculars, and ensure the eye relief vs eyecup depth is working well for you. I have trouble with some binos there, including the UV 42 models.
Thanks for sharing your experience. With the difference in evening performance being so subtle to be almost negligible, what are other advantages of using a 42 over a 32? 42's are bigger so that seems like a big sacrifice. I'm debating weather I should return the 42's, but would be interested in hearing other's thoughts about why a 42 over a 32 would be worthwhile besides twilight. Despite the image being almost the same, they do seem somehow easier on the eyes to me (better focal length?) but wonder if others think the trade-offs are worth it.
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Old Tuesday 20th August 2019, 03:19   #10
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Despite the image being almost the same, they do seem somehow easier on the eyes to me (better focal length?) but wonder if others think the trade-offs are worth it.
42s have long been considered the default, all-around compromise, but it's completely a matter of individual taste, and 32s seem to have gained ground recently. A larger exit pupil can give more comfortable viewing, especially in low light... if this is what you mean by "easier on the eyes", you may end up preferring a 42 after all. To me, it's a pretty small difference (again) until I step up to 50 or 56mm, so most of the time I want my compact 32, and otherwise something really large. You might enjoy trying a 50/56 just as a comparison; you will see a difference, though possibly still less than you would have imagined. It takes a large difference in brightness to be clearly noticeable, and pupil size ultimately limits how far that can go.
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Old Tuesday 20th August 2019, 07:57   #11
Mike F
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This has raised a question in my mind. Am I correct in thinking that there should be more difference in brightness between a 32 and 42 than there would be between a 42 and a 50? It seems, looking at the actual differences in objective lens size (10mm and 8mm), and the relative percentage difference in size, that there should be more difference between 32 and 42 than between 42 and 50. I've always assumed that was one of the reasons why 42's are usually considered as the 'sweet spot' compromise between optical performance (including brightness) and size/weight.

If that's the case and it's hard to detect a difference between the brightness of a 32 and 42, then the very little extra gain of the 50 over the 42 would make a good case for sticking with the 32! I have to confess that 32 is the only (normal) format which I don't currently own, having a 25, 42 and 50. Maybe I should treat myself to the delights of the 32 format?!
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Old Tuesday 20th August 2019, 08:53   #12
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This has raised a question in my mind. Am I correct in thinking that there should be more difference in brightness between a 32 and 42 than there would be between a 42 and a 50? It seems, looking at the actual differences in objective lens size (10mm and 8mm), and the relative percentage difference in size, that there should be more difference between 32 and 42 than between 42 and 50.
In broad daylight, your eye pupils will be smaller than the binocular exit pupil and then brightness of the view is determined solely by the transmission of the instrument.

At night your eye pupils will be larger than the exit pupil and then the brightness is determined first and foremost by the exit pupil size. Transmission makes just a minor modification on that. Take 8x42 and 10x50, the exit pupil sizes are 5.25mm and 5mm respectively, so the 8x42 will be a bit brighter (there's 10% more light in its exit pupil). But take an 8x50 and that will be 42% brighter than an 8x42.
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Old Tuesday 20th August 2019, 11:57   #13
Mike F
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But take an 8x50 and that will be 42% brighter than an 8x42.
Yes, thanks - of course it depends on exit pupil size rather than objective lens size doesnt it, but I dont understand how 8x50 is 42% brighter than a 8x42. Not doubting you necessarily - just dont understand.......
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Old Tuesday 20th August 2019, 12:23   #14
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Hi,

it's not about diameter but about area...

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Old Tuesday 20th August 2019, 14:22   #15
Moose8
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In broad daylight, your eye pupils will be smaller than the binocular exit pupil and then brightness of the view is determined solely by the transmission of the instrument.
This also raises another question for me. A lot of reviews I've read of 8x42 binoculars tend to say something along the lines of larger objectives allowing better views on cloudy days or under forest canopy than the 32 format.

But I have to ask, even on the dimmest, cloudiest day under a forest, the ambient light conditions are still much, much brighter than at the magic 15 minute window at total dusk when colors begin to desaturate and when the pupil size dilation should definitively matter.

Is there any sense in which a 42 would have a brighter view than a 32 overall? What are these reviews talking about when they say they perform better under clouds? Even on the most miserable day I would think it wouldn't be dark enough to dilate pupils above 4mm, but am I wrong?
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Old Tuesday 20th August 2019, 14:25   #16
Mike F
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Hi,

it's not about diameter but about area...

Joachim
Ah yes, of course! According to my maths though, that would still mean that there is a greater difference between 32 to 42 than there is between 42 to 50. But I realise that it's about exit pupil and if one can take advantage in low light of the greater exit pupil of a 50 vs 42. Here again it seems likely that most people would more easily notice the difference between a 32 and 42 than a 42 and 50. Or am I mistaken? (I presume we are talking about 8x bins)
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Old Tuesday 20th August 2019, 15:39   #17
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Although old I can easily see that my Swift HR/5 8.5x44 is brighter than the 8x32 Leica BA at night.
My pupils are still over 5.25mm even with severe light pollution.

However, there is lot of glare and flare with the Swift, so if there is a streetlight the Leica 8x32 BA is much much better.

If under dim room light someone looks at your pupils against a ruler and sees that they are 5.25mm or wider then an 8x42 is useful in twilight. Each pupil can be different.

In cloudy conditions a young person can easily have pupils bigger than 4mm.

When I look at movies with young actors, the pupils are often huge, sometimes up to 9mm.
Another fairly young actor has tiny pupils, maybe 2mm indoors. This can be a medical condition or the result of ingesting something.

People vary.

B.
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Old Tuesday 20th August 2019, 15:59   #18
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I have to ask, even on the dimmest, cloudiest day under a forest, the ambient light conditions are still much, much brighter than at the magic 15 minute window at total dusk when colors begin to desaturate and when the pupil size dilation should definitively matter.

Is there any sense in which a 42 would have a brighter view than a 32 overall? What are these reviews talking about when they say they perform better under clouds? Even on the most miserable day I would think it wouldn't be dark enough to dilate pupils above 4mm, but am I wrong?
I think the math and physics on one side are pretty clear and straightforward, but on the other side the interaction with our eyes and brain is something else entirely.

Case in point, just two days ago I was comparing 8x42 and 10x42 on a dull cloudy day and noticed that in the deep shadows the 8x42 showed a slightly brighter and more colourful view.

Fast forward half a day, it cleared out in the evening, and looking at the night sky in deepening twilight I struggled to see a brightness difference between these two instruments. They appeared much closer than in daytime. Can't really explain that.
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Old Tuesday 20th August 2019, 16:03   #19
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Mark,

The cones and rods of the eyes respond differently under different light levels.

B.
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Old Tuesday 20th August 2019, 16:04   #20
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Ait seems likely that most people would more easily notice the difference between a 32 and 42 than a 42 and 50. Or am I mistaken? (I presume we are talking about 8x bins)
8x32 has 4 mm exit pupil;
8x42 has 5.25 mm exit pupil, that is 72% larger by area than 8x32;
8x50 has 6.25 mm exit pupil, that is 42% larger by area than 8x42.

So yes objectively the step in night sky brightness going from 8x32 to 8x42 is bigger than going from 8x42 to 8x50.
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Old Tuesday 20th August 2019, 16:25   #21
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One way to eliminate nearly all the variables except exit pupil is to make a 32mm aperture mask and place it in front of one side of your 8x42. Using one eye, switch back and forth between the two sides.
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Old Tuesday 20th August 2019, 16:37   #22
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And then put the mask in front of the other barrel or turn the binocular upside down (:

Or do both, as the transmission could differ between barrels in an older binocular, as well as differences between eyes.

B.
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Old Tuesday 20th August 2019, 17:23   #23
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8x32 has 4 mm exit pupil;
8x42 has 5.25 mm exit pupil, that is 72% larger by area than 8x32;
8x50 has 6.25 mm exit pupil, that is 42% larger by area than 8x42.

So yes objectively the step in night sky brightness going from 8x32 to 8x42 is bigger than going from 8x42 to 8x50.
Hi Mark

I can't work out your maths. I make it

32 to 42 = 58% increase (in area)

42 to 50 = 70.5% increase

So going from 42mm to 50mm objective is more noticeable in theory than 32mm to 42mm.
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Old Tuesday 20th August 2019, 17:45   #24
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Hi Mark

I can't work out your maths. I make it

32 to 42 = 58% increase (in area)

42 to 50 = 70.5% increase

So going from 42mm to 50mm objective is more noticeable in theory than 32mm to 42mm.
I did (5.25 / 4)^2 = 1.72 and (6.25 / 5.25)^2 = 1.42. I don't know what you did, sorry.
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Old Tuesday 20th August 2019, 18:19   #25
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I did (5.25 / 4)^2 = 1.72 and (6.25 / 5.25)^2 = 1.42. I don't know what you did, sorry.
I worked out the area for each exit pupil and then the %age increase.

Pi x Radius squared gives area so 3.14x4 for 32mm gives 12.56 and so on...
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