Daytime benefit of large objectives? (2 Viewers)

[etc]

You can't really find the new model 8x56 SLC used yet. It just came into the US just lately and there isn't any on the used market yet. It is probably not a huge volume binocular either like an 8x42. I had to pay retail for mine from Eurooptics which was $2150.00. Then once people use them and see how good they are they won't sell them. I haven't seen much price drop on the SF either especially the black model. It is holding firmly in that alpha +$2500.00 range. I did see a LNIB black Zeiss SF 8x42 go for about $1750.00 on Ebay a few months ago. I threw a bid in but was outbid.

Around 1700 would be a sweet deal for the latest generation Zeiss SF.

I think it will get there in a year or two.

 

[Theo98]

I think those articles are examples of people seeing something they like, but not not understanding why. I do tend to a agree with the Audubon author that areas of deep shadow in daylight often do look more vivid and detailed in large exit pupil binoculars compared to small ones. I think that's because the eye is often dilated to an unexpectedly large aperture when viewing through binoculars in daylight. I've measured my pupil dilation (using the defocused artificial star method) at various levels of daylight with a binocular in front of my eyes and was surprised to find that deep shadow areas cause a dilation of close to 4mm even on sunny days and around 5mm on cloudy days.

Another effect that tends to make the overall FOV appear a little brighter in large exit pupil binoculars compared to small ones in bright daylight conditions is that a vignetted off-axis 7mm exit pupil has a larger surface area than an equally vignetted 4mm exit pupil. Typically, the minor axis of an almond shaped vignetted 7mm exit pupil in the outer parts of the FOV will still be wider than the diameter of the eye's pupil in bright light, allowing the eye to admit all the light it can, even close to the edge of the field. The minor axis of that same amount of vignetting from a 4mm exit pupil will likely be smaller than the diameter of the eye pupil and cause some gradual dimming of the image in the outer half of the field compared to the 7mm exit pupil.

Interesting, and another great explanation...Thanks Henry!

Ted

 

[[email protected]]

Like this?

Is that the older SLC on the right? Here is a great story about the SLC.

https://www.opticsreviewer.com/swarovski-slc-hd.html

 

[[email protected]]

I think those articles are examples of people seeing something they like, but not not understanding why. I do tend to a agree with the Audubon author that areas of deep shadow in daylight often do look more vivid and detailed in large exit pupil binoculars compared to small ones. I think that's because the eye is often dilated to an unexpectedly large aperture when viewing through binoculars in daylight. I've measured my pupil dilation (using the defocused artificial star method) at various levels of daylight with a binocular in front of my eyes and was surprised to find that deep shadow areas cause a dilation of close to 4mm even on sunny days and around 5mm on cloudy days.

Another effect that tends to make the overall FOV appear a little brighter in large exit pupil binoculars compared to small ones in bright daylight conditions is that a vignetted off-axis 7mm exit pupil has a larger surface area than an equally vignetted 4mm exit pupil. Typically, the minor axis of an almond shaped vignetted 7mm exit pupil in the outer parts of the FOV will still be wider than the diameter of the eye's pupil in bright light, allowing the eye to admit all the light it can, even close to the edge of the field. The minor axis of that same amount of vignetting from a 4mm exit pupil will likely be smaller than the diameter of the eye pupil and cause some gradual dimming of the image in the outer half of the field compared to the 7mm exit pupil.

Good explanation of what I see with the SLC 8x56. I believe you are correct in that people are seeing something they like but not really understanding why. The SLC 8x56 gives me an aberration free, flare free and CA free view so whatever is going on with that bigger aperture it seems to work.

 

[[email protected]]

Around 1700 would be a sweet deal for the latest generation Zeiss SF.

I think it will get there in a year or two.

If they don't discontinue them like the HT's!

 

[typo]

Henry,

I have tried your method before, but haven't collected much data as the sunshine isn't always obliging over here. After a pretty miserable couple of months the sun has returned, and prompted by today's post, I gave it another go. These measurements were between 4:15 and 4:30 today. There was light cloud and the sunshine was pretty hazy. I just took 8 estimates round the back yard. 3 had some sky in the field of view, and others at ground level, including against the darkest foliage I could find. Luminance values ranged from approximately 600 cd/m2 to 5500cd/m2, using a photographic light metre. That gave a range of 1.9mm to 2.5mm pupil diameters. If the sun is obliging I'll try some more measurement nearer sunset.

Just an anecdote from a couple of years ago. I was in the company of some very capable birders one weekend, and as daylight faded and they gave up birding and returned to base I managed to get pupil diameter estimates from just a few of them. They ranged between 4 and 4.5mm.

David

P.S. Going out just before sunset I followed the luminance level from 64cd/m2 down to 2.7cd/m2 when blues and reds were beginning to darken significantly. My corresponding pupil diameter started at 3.6mm and increased to 4.5mm which was the limit I was able to measure using natural light. Though they are still able to dilate to at least 5.4mm if required.

 

[wdc]

I do tend to a agree with the Audubon author that areas of deep shadow in daylight often do look more vivid and detailed in large exit pupil binoculars compared to small ones. I think that's because the eye is often dilated to an unexpectedly large aperture when viewing through binoculars in daylight. I've measured my pupil dilation (using the defocused artificial star method) at various levels of daylight with a binocular in front of my eyes and was surprised to find that deep shadow areas cause a dilation of close to 4mm even on sunny days and around 5mm on cloudy days.

The same is true with landscape painting in the field. If one is painting a motif where a large mass of shadow, or dark values are present in the scene, the eye will dilate, allowing one to see into the shadows more. Binoculars are not required for this effect to occur! The use of umbrellas when painting outdoors
can help maintain a stable lighting environment, not only for the painting, the palette of colors, but also for the artist's eyes.

-Bill

 

[Troubador]

That's true, and you would include other factors like time of day, age, medication and disease. The take home message is that, even though there are fairly large swings in retinal light flux and it's there pretty much all the time, you can't tell it's happening.

David

If you are alert and interested (ie mentally engaged) as in looking through binos trying to see something or identify a species, doesn't this mean it is likely that hippus is not happening during this? Perhaps this isn't known at the present time.

Lee

 

[typo]

Lee,

I'm not paying to read the experimental detail of those particular papers, but what seems to be relevant from other work is that when the observer focusses on foveal (high detail) information the eye/brain/iris is significantly less responsive to retinal flux regulation. On the face of it, it seems to decrease brightness perception.

David

 

[Tringa45]

Another effect that tends to make the overall FOV appear a little brighter in large exit pupil binoculars compared to small ones in bright daylight conditions is that a vignetted off-axis 7mm exit pupil has a larger surface area than an equally vignetted 4mm exit pupil. Typically, the minor axis of an almond shaped vignetted 7mm exit pupil in the outer parts of the FOV will still be wider than the diameter of the eye's pupil in bright light, allowing the eye to admit all the light it can, even close to the edge of the field. The minor axis of that same amount of vignetting from a 4mm exit pupil will likely be smaller than the diameter of the eye pupil and cause some gradual dimming of the image in the outer half of the field compared to the 7mm exit pupil.

Henry,

I think you've hit the nail on the head there.
In hand-held use the pupils will be displaced laterally when viewing the field edges. Assuming an eye diameter of 24 mm the pupil would be about 11 mm from the centre and rotation of 30° would result in a lateral eye pupil displacement of 5,5 mm, enough to cause vignetting even with large binocular exit pupils.
When viewing the field edges from a tripod a lateral movement of the head in the opposite direction can compensate to some extent and this also reduces lateral CA .

John

 

[ailevin]

This is a very interesting thread particularly this latest insight about vignetting.

I claim no expertise in binocular design and engineering, but my own experience and other user reports seem to indicate that glare and stray light control (internal reflections and scattering) are harder with smaller aperture binoculars. I don't know if it is because with smaller objectives the designer is striving for compactness or if it is something more fundamental optically.

Alan

 

[tenex]

I think those articles are examples of people seeing something they like, but not not understanding why. I do tend to a agree with the Audubon author that areas of deep shadow in daylight often do look more vivid and detailed in large exit pupil binoculars compared to small ones. I think that's because the eye is often dilated to an unexpectedly large aperture when viewing through binoculars in daylight. I've measured my pupil dilation (using the defocused artificial star method) at various levels of daylight with a binocular in front of my eyes and was surprised to find that deep shadow areas cause a dilation of close to 4mm even on sunny days and around 5mm on cloudy days.

Another effect that tends to make the overall FOV appear a little brighter in large exit pupil binoculars compared to small ones in bright daylight conditions is that a vignetted off-axis 7mm exit pupil has a larger surface area than an equally vignetted 4mm exit pupil. Typically, the minor axis of an almond shaped vignetted 7mm exit pupil in the outer parts of the FOV will still be wider than the diameter of the eye's pupil in bright light, allowing the eye to admit all the light it can, even close to the edge of the field. The minor axis of that same amount of vignetting from a 4mm exit pupil will likely be smaller than the diameter of the eye pupil and cause some gradual dimming of the image in the outer half of the field compared to the 7mm exit pupil.

Good points: it's not just physics, but a combination of physics and biology. And language... I don't think I see more detail with a larger EP in smaller shadow areas among brighter ones, but think I do looking into larger areas of full shadow. Thanks for explaining the potential effect of vignetting on perceived overall brightness too. I think all this just gets too complicated for people trying to explain the benefits of larger binoculars.

Anyone want to tackle "better color rendition"?

 

[[email protected]]

This is a very interesting thread particularly this latest insight about vignetting.

I claim no expertise in binocular design and engineering, but my own experience and other user reports seem to indicate that glare and stray light control (internal reflections and scattering) are harder with smaller aperture binoculars. I don't know if it is because with smaller objectives the designer is striving for compactness or if it is something more fundamental optically.

Alan

Henry answered that question in his review of the Zeiss 8x56 FL. I have also noticed that smaller aperture binoculars are more prone to flare and the 8x56 SLC has no flare at all.

"The 7mm exit pupil also has a benefit in daylight. There is virtually complete freedom from “flare”. When bright reflections from the edge of the objective reach the eye they are out at the edge of a 7mm circle of light, so the flare tends to fall invisibly on the iris rather than entering the eye."

 

[chill6x6]

Is that the older SLC on the right? Here is a great story about the SLC.

https://www.opticsreviewer.com/swarovski-slc-hd.html

Yes...current version left and previous version right.

 

[typo]

Vignetting is not a topic I understand particularly well, but I'll try to explain what I've read and how I think it works in practice.

As illustrated in text books, it is not so much a function of the binocular exit pupil, but the observer's pupil diameter. When the pupil is tiny the fraction of the apparent angle of view that is affected by vignetting is small. As the pupil dilates, thr degree of vignetting increases, and potentially the edges would darken for on axis viewing, up to the point in decreasing light where the exit pupil was limiting. So in theory a large EP binocular might potentially have greater edge darkening than a small one.

I think the situation is somewhat different when looking off axis. If your eye is aligned, not with the centre, but angled at something like 30° to the central axis, then the exit pupil may become elliptical and potentially reduce brightness. I say potentially, because exit pupils are rarely flat. Eyepiece design appears to be a factor. My 10x56 appears to be just as prone to off axis vignetting as my 10x42 at similar light levels, but I can't explain why.

David

 

[henry link]

Hi David,

You can use the defocused star method to observe your own eye's experience of off-axis vignetting at different light levels in different binoculars. Of course you'll have to look off axis to clearly see it, but it's there even for a centered eye since the prism aperture in all binoculars is too small to pass rays near the field edge without vignetting.

I wouldn't want to exaggerate the visible effect, which is subtle even though the last few degrees of apparent field show an exit pupil reduced to a slit.

Henry

 

[BruceH]

.........
The 8x56 SLC makes me want to try 8x42 SLC.
........

Here you go Dennis. A SLC 42mm model on the left next to the bigger SLC 56mm model as displayed in the Cabela's showcase.

 

[Theo98]

Here you go Dennis. A SLC 42mm model on the left next to the bigger SLC 56mm model as displayed in the Cabela's showcase.

View attachment 658584

Thanks Bruce,

Wow...if they were on even ground, appears the 56 would be Twice as tall as the 42!?! :eek!:

Ted

 

[BruceH]

Thanks Bruce,

Wow...if they were on even ground, appears the 56 would be Twice as tall as the 42!?! :eek!:

Ted

Hey Ted .... That is one hunk of a piece of glass. It makes the 42mm look like a Swaro CL in comparision.


Dennis .... How about posting a picture of your new model CL next to the the 56mm SLC. That would make for a cool visual and Chuck loves those comparison shots!

 

[typo]

Henry,

I did use your method to check off axis viewing with different binoculars. A phenomenon I've occasionally noticed in normal use. The periperal dimming with on axis viewing, I've only seen under lab type conditions, at light levels somewhat below those I'd normally encounter birdwatching.

I extended the test range into the mesopic light range low by using a pin hole in a pice of aluminium foil covering the lens of a low power torch. My meter isn't sensitive to get into the scotopic range.

David