Fullsize bins in the daytime (1 Viewer)

walternewton · May 2, 2011

It's often said here that the larger exit pupil you get with, say, a given model of fullsized binoculars vs. its midsized counterpart doesn't provide a brightness advantage except in the first few minutes of dawn or last few minutes of dusk (or in full dark, for astrononmical use), because when viewing under brighter conditions your eye's pupil is stopped down smaller than the binocular's exit pupil.

For those who prefer fullsized bins for general (that is, mostly daytime) use, do you find other advantages besides the "dawn, dusk & dark" performance that outweight the disadvantages of size/weight, cost, FOV that goes along with them?

Do you suscribe to Stephen Ingraham's notions that they perform better when viewing at long distances, or looking into shadowed areas?

Do you find the less finicky eye placement due to the larger exit pupil more comfortable?

Alexis Powell · May 2, 2011

For me, the big advantages of full-sized bins in daytime are (1) easy eye placement, including ability to rotate eyes off-axis to look around field of view, (2) generally better contrast, (3) greater mass and grip surface for a more steady view.

--AP

RJM · May 3, 2011

There are few birding binoculars sold with an exit pupil that matches our average 2.5mm daytime pupil diameter. Theoretically a small 10x25 compact should be all anyone needs. But I'd bet few, if any birders would choose these in a side-by-side test of brightenss with binoculars having 4-5mm exit pupils.

A larger exit pupil definitely makes a binocular easier/more comfortable in use. And as for brightness, most binoculars do not FULLY illuminate their exit pupils. In some, the illumination dropoff towards the edge is suprisingly severe and I think this is why despite the theory (more applicable to stargazing IMO) 4-5mm eixt pupil binos APPEAR to be brighter at least to my eyes. Moreover, any optical defects should be less apparent since you are predominately looking thru the central, fully illuminated area of the exit pupil. Finally, I'd like to think shade offered by the binocular eyecups lets our pupils dilate slighty larger when we bring them up to our eyes but I could be completely wrong since the dilation response might be affected more by direct light than indirect. Suppose one could test for change in their pupil size while looking thru a bino into a mirror.

ronh · May 3, 2011

Here's a couple of big-exit-pupil advantages proposed by Henry Link, which I think are true.

Glare, resulting from bright light just outside the field of view, is due to strong illumination of the inside of the binocular barrel near the objective lens. This light winds up just outside the exit pupil. The bigger the exit pupil, the less likely this unwanted light is to get into the eye.

When the eye's pupil is small than the binocular's exit pupil, the effective aperture is reduced. This is sometimes criticized by small-binocular advocates as "wasted glass". But, the effective focal ratio is increased by this circumstance, which decreases aberrations, and according to some experienced users, makes a visible improvement in image quality.

In the afternoon when darkening sets in, I can see that my eyes have already opened up to 4mm, just by looking in a mirror with a ruler. That's still pretty bright! 4mm does not cut it for me in low light.

My most overly big and overly big exit pupiled binocular is a 7x50. Wasted glass in spades you could say. But, its image, even in broad daylight, appears brighter to me than an 8x30 from the same series (Fujinon FMT-SX). It is the most glare-resistant of my small collection. And, its image has an undefinable "punch" to my eyes, even compared to a 8x42 Zeiss FL.
Ron

Kevin Purcell · May 3, 2011

walternewton;2130931Do you suscribe to Stephen Ingraham's notions that they perform better when viewing at long distances said:
People have covered all the main advantages of bigger exit pupil bins: glare (and because of that contrast), comfort and eye-placement, low light performance (for me that's pre-dawn and overcast for an hour or so after dawn).

But aside from those advantages I don't see where Stephen Ingraham claims come from especially the "looking into shadowed areas" claim. That would be a contrast issue (which varies rather more than exit pupil) not a exit pupil size issue. I've not seem him explain why he thinks this.

Of course this exit pupil size is a trade off with weight and FOV to some extent (32mm bins). For most daylight use a modern 8x30ish bin works fine for birding.

John S. · May 3, 2011

It's often said here that the larger exit pupil you get with, say, a given model of fullsized binoculars vs. its midsized counterpart doesn't provide a brightness advantage except in the first few minutes of dawn or last few minutes of dusk (or in full dark, for astrononmical use), because when viewing under brighter conditions your eye's pupil is stopped down smaller than the binocular's exit pupil.

For those who prefer fullsized bins for general (that is, mostly daytime) use, do you find other advantages besides the "dawn, dusk & dark" performance that outweight the disadvantages of size/weight, cost, FOV that goes along with them?

I find that 8x32 and 8x30 full size binoculars balance the inevitable trade-offs in performance between the various configurations. I really don't want dawn to darkness performance in one binocular. Beyond strengthening neck muscles I find little value in lugging 42mm, 50mm or 60mm bins around.

Do you suscribe to Stephen Ingraham's notions that they perform better when viewing at long distances, or looking into shadowed areas?

For the most part yup.

Do you find the less finicky eye placement due to the larger exit pupil more comfortable?

Not really an issue for me since the smallest exit pupil bins I have are 3mm and most of my birding is done at 3.5 to 5mm.

looksharp65 · May 3, 2011

walternewton said:
Do you suscribe to Stephen Ingraham's notions that they perform better when viewing at long distances, or looking into shadowed areas?

When I owned the excellent Minox HG 8x33 (exit pupil 4.1 mm, great transmission and contrast) and tried my Fury 6.5x32 (exit pupil 4.9 mm) the difference was significant.

It was broad daylight and I watched small shadowed areas in a nearby crown of tree. The Fury was significantly brighter. But when I compared them by watching an evenly lit meadow with yellow grass, the difference was very minute.

I concur with the words on easy eye placement and glare resistance.

Kevin Purcell · May 4, 2011

looksharp65 said:
When I owned the excellent Minox HG 8x33 (exit pupil 4.1 mm, great transmission and contrast) and tried my Fury 6.5x32 (exit pupil 4.9 mm) the difference was significant.

It was broad daylight and I watched small shadowed areas in a nearby crown of tree. The Fury was significantly brighter. But when I compared them by watching an evenly lit meadow with yellow grass, the difference was very minute.

That's a magnification realted brightness effect not an exit pupil size effect: lower magnification bins have higher brightness (brightness is photons per unit solid angle not the total intensity of light out of the ocular of the bin).

You need to keep one constant whilst varying the other parameter to see any real effect.

But perhaps that's why Ingraham said that as larger exit pupil bins usually come with lower magnifications. Maybe he noticed the brightness change in 7x40, 8x40 and 10x40 bins and drew the wrong conclusion?

Fullsize bins in the daytime (1 Viewer)

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walternewton

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Alexis Powell

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RJM

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ronh

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Kevin Purcell

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John S.

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looksharp65

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