Your advice -- the addition of 8x42 for over 55 years users (1 Viewer)

Which is pretty much what I wrote way back in post #9, but with simpler math. However, after Troubador's second post, I got spooked, thinking that Henry would come out of the cyber shadows and throw in an "x-factor" as he often annoyingly but correctly does.

Thanks for that more thorough explanation, Pileatus.

Now let me throw a "Spaniard in the Works". I discovered that the enhanced apparent contrast created by different color balances can make the view (and specific objects in the view) look brighter even in a smaller aperture bin despite the fact that the numbers show the larger aperture bin should look brighter.

The case I argued with Henry was the 8x30 EII vs. the 8x32 SE. The color balance on the EII gave enhanced contrast that made birds (particularly robins, with their starkly contrasting red and black) look brighter than through the 8x32 SE even as light levels dropped when the SE should have had the advantage.

Now that I have the latest 8x32 SE (550xxx), which has more advanced coatings, different glass, and better contrast than the 505xxx model I had then, the gap btwn the older 8x30 EII and the newer 8x32 SE has almost closed.

On some objects, the EII still seems a bit brighter due to color contrast, but overall, the difference is harder to tell apart.

Brock

Just to add a few more numbers.

8x56
Twilight factor 21.46
Area= 2463mm
EP =7mm
At 5mm pupil, 1256mm2 of objective used

10x56
Twilight factor 23.7
Area =2463mm
EP = 5.6mm
At 5mm pupil, 1962mm2 of objective used

I think that says if your maximum pupil diameter is 5mm, a 10x56 will be a pretty useful option. Seems to tally with my experience.

David

Very interesting, particularly as to how it relates to the twighlight factor.
I'm not clear on one point though - at a 4mm pupil dilation, the 10x42 has 56% more useful objective area (in mm2) than a 8x42, but presumably the image is no brighter (if it were, then presumably the pupil would dilate past 4mm). So if the useful objective area (in mm2) can be though of as photon transmission, what is happening to the extra photons transmitted, or aren't there any (in which case I need to brush up on more physics)? Or does it mean that at the same ambient light level, your pupil will dilate less/constrict more using a 10x42 compared to a 8x42 because it is brighter?

The 10x42 will have a smaller true field of view, so it is collecting photons from a smaller region of the scene than the 8x42. It does have a larger effective aperture, however, as you say. If the apparent fields of view of the 8x and the 10x are the same, these effects cancel, and the same number of photons reach your eyes in either case.
Ron

Do photons exist?

"The atoms of Democritus
And Newtons particles of light"

http://www.poemhunter.com/poem/mock-on-mock-on-voltaire-rousseau/

Bob

Pileatus, Typo and Brocknroller have pretty much summed up the tech behind the question and my sneaky feeling that 42 mm bins carry a greater density of light turns out to be totally mistaken.

This question is of great interest to me as my age is well, well, well into double figures (LOL). I wear spectacles and these do not help the accurate placement of bins in line with the eyes at all. So the larger EP of 42mm bins is a big benefit for me. And if your pupils ever dilate to more than 4.0 mm then using 32 mm bins means that for this portion of time you are not getting the best from your own eyes.

Its such an individual question that only testing out 32s against 42s can give an answer for any one person.

I will stick to 42mm bins until the weight becomes intolerable.

Much of the discussion about 32mm vs 42mm has been on the unspoken assumption of equal light transmission. Throw in Zeiss's claims for an extra 5% for the forthcoming 42mm VictoryHTs and here is another variable to throw in the mix!

ibramr said:

Friends,

I am relatively a new member in this group, and have greatly enjoyed reading your threads.

I am a very happy owner of Zeiss (FL 8x32) and Leica binoculars (Ultravid 8x20, and Trinovid 10x32). They provide me with tremendous joy in my urban walks, nature hikes, and bird watching. If I have any thing to say that I need--particularly for nature walks and bird watching--it is the desire to have a slightly brighter view around the sunset time.

Therefore, maybe, the addition of 8x42 would be helpful in this matter......but, I heard that users over 50 (I am now closer to 60s) can not really make use of the additional light the 8x42 can theoretically provide (because eyes cannot dilate large enough for the light to pass). To what extent is that true and pervasive? Please share your experience and let me know of your thoughts regarding this point.

Many thanks.

Click to expand...

Hello ibramr

I also own the Zeiss 8x32FL and found your question interesting.

A wee bit off topic but I have just came back from a walk with my dog in an Oak wood as the Sun was setting after 3 very warm days, 27 degrees celcius today (for Scotland in May that is unusual), the Suns light was horizontal and luminous orange creating a wonderland out of my usual walk. I decided to leave my binoculars at home on this particular occasion and im glad I did. I'm only 35 and do not have the pupil dilation problems you refer to (I have that to look forward to!).

Perhaps it doesnt answer your question but I think that just using your own eyes rather than binoculars can be a more interesting and natural 'magical' experience during the Gloaming.

Best regards
Brendan

An input from a late 60's - I use two 8x30ish bins for general use - one being the Zeiss FL. I own several other bins of varying powers and objectives so have a bit of a feel for older eyes and low light.

I find for low light a lot depends on what you are looking at - for general use I jump straight to some 7x42 FLs, however for specific detail (bird in tree) I frequently move to 10x skipping 8x42 as for me they are not significantly better than the 8x32 FL.

If I do use an 8x it is more likely to be a porro (actually the 10x is likely to be a porro as well as the objective seperation works well for me in low light).

I used to use 7x50 porros into my 50's but found that they ceased to be an improvement over a 7x40 effectively some years ago.

The one thing I have benefitted from all my life is that I havn't lived anywhere for very long that had street lighting, so luckily my night vision is still excellent which possibly counts for more than the glass a lot of the time.

Just read Brendan, I agree, also dusk/nocturnal/early morning wildlife is far less worried by one or two quiet humans than their daytime equivalents, just be aware of the wind direction (this applies to sound as well as scent).

Friends,

I would like to thank you all and every one of you for the wonderful insights and advice. It is very kind of you and I really appreciate it.

What are the next steps? I am--slowly--considering acquiring a 7x42 or 8x42. Meanwhile, I will enjoy what I have till the appropriate pair shows up.

Once more, thank you very much.

ronh said:

The 10x42 will have a smaller true field of view, so it is collecting photons from a smaller region of the scene than the 8x42. It does have a larger effective aperture, however, as you say. If the apparent fields of view of the 8x and the 10x are the same, these effects cancel, and the same number of photons reach your eyes in either case.
Ron

Click to expand...

That was a word puzzle, particularly this sentence: It does have a larger effective aperture, however, as you say.

Which means, what? Aperture trumps AFOV?

Let me see if I'm groking you. Are you saying that two bins with the same aperture, the one with a larger AFOV delivers more photons to your eyes than one with a smaller AFOV even if they both have equal light transmission????

How important is aperture, then? Would the larger AFOV of my 8x30 EII (70*) trump the 8x32 SE (60*) in packing in the photons if > AFOV = > photons, or as Henry has said and shown with photos, the 2mm larger aperture SE trumps the smaller aperture EII in brightness regardless of its smaller AFOV?

Does "brightness" mean the same thing as "collects more photons"?

B.

Brock,
The question was of the total amount of light coming through two binoculars, 8x42 and 10x42.

One component is, the area of the scene from which light is collected. That is the TFOV. Here, the lower magnification binocular will win. If the AFOVs are the same, the TFOV of the 8x will be the greater, by the factor 10/8.

The other main component is, the aperture available for the light to be collected into. Although both binoculars are 42mm, under the stated moderate low light conditions in which the eye's pupil is 4mm, the effective aperture of the 8x42 will be significantly reduced to (4/5.25)x42 mm. The effective aperture of the 10x42 will be reduced too, but only a very little bit, to (4/4.2)x42 mm.

The total amount of light that either puts into the eye will be the product of its observed field and its effective light collection aperture.

The 8x42 is bigger in its observed field than the 10x42, but smaller in effective collection diameter. (4/5.25)x(10/8)=.952 is a number that scales with its photon throughput.

The 10x42 is smaller in its observed field, but larger in effective collection aperture. I have already imposed the correction factor for observed field on the 8x42, so the 10x42 does not require a correction for that. So, its corresponding parameter is (4/4.2)x1=.952

These values are relative geometric factors, and not of much use outside the above rant.

Of course this is an ideal case I picked to give a neat result. In real life, 10x42s usually have larger apparent fields than 8x42s and would win by a little bit. And "percent transmissivity" is another factor, that I have ignored, but can vary significantly. Also, a correct calculation of amount of light throughput, in the case where there turned out to be a difference, would have to be done in terms of areas. I only dealt in diameters, which I can in this case, since equal diameters contain equal areas.

Any other case, like your proposed EII vs SE comparison, should be worked in detail, with an assumed eye pupil diameter. Certainly, the EII would win this contest by virtue of its huge apparent field.

No, this is not the same as what I think of as "brightness", or "surface brightness" which is better described as (total light/angular area). Now THAT is an interesting parameter that I think easily relates to quality of view.

Ron

ronh said:

No, this is not the same as what I think of as "brightness", or "surface brightness" which is better described as (total light/angular area). Now THAT is an interesting parameter that I think easily relates to quality of view.

Click to expand...

Ron,

Very interesting, but rather confusing. Seems paradoxical to my little brain.

The light from an object makes the same same angle to the objective, so the same amount of light is collected. However when viewed at 10x the object appears bigger than 8x, so doesn't that say the perceived light per object area should decrease; appear dimmer. Conversely the available light from that object is concentrated into a smaller area at the higher magnification, which sounds like it should be brighter. Do they cancel each other out? It doesn't seem to in practice. You can, or at least I can discern more detail at a higher power in low light providing the EP on both is larger than you eye pupil, just like the 'twilight factor' numbers suggest.

Can you explain in simple terms what's happening?

David

P.S. I can just about cope with a lumen, watt, and steradian, but would rather not.

typo said:

You can, or at least I can discern more detail at a higher power in low light

Click to expand...

I'm just making this up to provoke a response from an expert: Spreading the image over a larger area of the retina helps for detecting details, especially linear features and at low enough light levels that cones and the fovea start to give way in utility to rods and the overall retina.

--AP

Typo,
In the case where the observer's eye is 4mm, the effective aperture of the 8x42 is significantly less than that of a 10x42. So less light from a given object is transmitted to the eye by the 8x42. Now consider the light spreading effects of the different magnifications on the illumination of the image. Less light spread over a smaller apparent area in the 8x, and more light spread over a larger apparent area in the 10x. The surface brightness of the object seen through the two binoculars is the same. The object will be seen better in the 10x, because it looks bigger.

Any time the eye pupil is filled, or over-filled, with the exit pupil of the binocular, you have a special case, exactly as you say. Then, the surface brightness will be as great as optically possible under those lighting circumstances. Of course good coatings, with their higher percent transmissivity, will also be an important factor, and lots of other things also contribute to the quality of the view. But I am concentrating on the geometry effect.

I'm no expert, I only love this stuff. Sorry if I (1)don't explain well or (2) am wrong as hell!
Ron

ronh said:

Typo,
In the case where the observer's eye is 4mm, the effective aperture of the 8x42 is significantly less than that of a 10x42. So less light from a given object is transmitted to the eye by the 8x42. Now consider the light spreading effects of the different magnifications on the illumination of the image. Less light spread over a smaller apparent area in the 8x, and more light spread over a larger apparent area in the 10x. The surface brightness of the object seen through the two binoculars is the same. The object will be seen better in the 10x, because it looks bigger.

Any time the eye pupil is filled, or over-filled, with the exit pupil of the binocular, you have a special case, exactly as you say. Then, the surface brightness will be as great as optically possible under those lighting circumstances. Of course good coatings, with their higher percent transmissivity, will also be an important factor, and lots of other things also contribute to the quality of the view. But I am concentrating on the geometry effect.

I'm no expert, I only love this stuff. Sorry if I (1)don't explain well or (2) am wrong as hell!
Ron

Click to expand...

Lol! Love it Ron! Yes, we can understand and no your not wrong as hell!!! Bryce...

Thanks Ron, that's pretty much as I suspected, though rather better stated, but it still seems to understate the benefit I seem to see in practice. Guess we're looking at the optophysiology of the eye which is even more puzzling than regular optics.

I compared a few of my pairs as things turned black. In particular looking for the limits of colour vision. No test targets or anything like that, just a pale green bush at the bottom of the garden in front of a hedgerow well shaded by trees. I used four binos, a 7x26 twilight factor 13.5, 7x36 TF 15.9, 12x46 TF 23.5 and a 10x58 TF 24.1.

The 7x26 and 7x36 were surprisingly close. At the point where the bush was a barely visible, feint green blob against shades of grey with the 7x26, the x36 showed just a little more definition, making the outline a fraction more distinct. The advantage of a 5.1 EP over the 3.7 was there but nowhere near the the 90% difference tha EP ratio would suggest, making me suspect that at that moment my pupil diameter wasn't allowing me to gain the full benefit.

The 12x46 with an EP of 3.8 was probably no brighter than the 7x26, but there was a big difference in detail visible with most of the leaves being distinguishable. I think that speaks to what what you said about bigger being better. Just the cone resolution at this light level is so bad that the extra magnification makes a big difference to the level of detail. The 10x58 was in a different league, not only appearing brighter than the 7x36, but every leaf was visible, with the veining evident on most. I don't know how long the cat had been hunting in the hedgerow but I hadn't spotted it with the others. I only had chance to switch back to the 7x36 before it had moved off, and although I could detect the movement I still wouldn't have known what it was.

Of course the transmission is another element. They are all strong performers in the green at least (but rather different in the blue), and I doubt there was anything more than a few percent of difference between them.

What I don't know is what my pupil diameter was at the time, but there is little doubt that magnification was a winner in these very low light levels. I like a 7x, got two already, but I'm sure I'm not going to get any useful advantage with a 7x42 over a 7x36 in low light conditions these days. I imagine a 8x42/50 would be an improvement, a 10x56 is substantially better, and I would expect a 12x70 better still. I'll settle for the 10x56.

David

David,
I absolutely agree. Surface brightness is not that big a deal. Magnification wins, as high as you can handle it.
Ron

ibramr said:

Friends,

I am relatively a new member in this group, and have greatly enjoyed reading your threads.

I am a very happy owner of Zeiss (FL 8x32) and Leica binoculars (Ultravid 8x20, and Trinovid 10x32). They provide me with tremendous joy in my urban walks, nature hikes, and bird watching. If I have any thing to say that I need--particularly for nature walks and bird watching--it is the desire to have a slightly brighter view around the sunset time.

Therefore, maybe, the addition of 8x42 would be helpful in this matter......but, I heard that users over 50 (I am now closer to 60s) can not really make use of the additional light the 8x42 can theoretically provide (because eyes cannot dilate large enough for the light to pass). To what extent is that true and pervasive? Please share your experience and let me know of your thoughts regarding this point.

Many thanks.

Click to expand...

I think you have too much money.....

rosbifs said:

I think you have too much money.....

Click to expand...

Really, what kind of comment is that?

stereotruckdriver said:

Really, what kind of comment is that?

Click to expand...

Just being facetious.

Although one pair of zeiss and two pairs of leica.....