Daytime benefit of large objectives? (1 Viewer)

While looking at small structure, i.e. pine needles, small scale wood bark at distance, and I compare the 8X42FL and 8X56FL, I get better resolution with the 8X56 than the 8X42. I see more detail of these structures.

Andy W.

dries1 said:

While looking at small structure, i.e. pine needles, small scale wood bark at distance, and I compare the 8X42FL and 8X56FL, I get better resolution with the 8X56 than the 8X42. I see more detail of these structures.

Andy W.

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Andy. Do you get less aberration with the bigger 56mm FL's? Does the view appear clearer and more transparent? How about glare and CA between the two FL's?

dries1 said:

While looking at small structure, i.e. pine needles, small scale wood bark at distance, and I compare the 8X42FL and 8X56FL, I get better resolution with the 8X56 than the 8X42. I see more detail of these structures.

Andy W.

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I hope it's OK if I pull out this this old post yet again.

https://www.birdforum.net/showpost.php?p=3424981&postcount=17

It shows pretty well how a low aberration image can look sharper and higher contrast than a higher aberration image without actually resolving any smaller quantifiable detail at the limit of eyesight acuity. The 8x42 FL (stopped down to 30mm) would look better than the 8x30 Habicht in this comparison, but I can still see a difference in sharpness and contrast between my 8x42 and 8x56 FLs that makes it seem like the 8x56 should be showing me smaller details even though I can't actually resolve smaller line pairs with it.

Henry

Henry,

"I can still see a difference in sharpness and contrast between my 8x42 and 8x56 FLs that makes it seem like the 8x56 should be showing me smaller details even though I can't actually resolve smaller line pairs with it."

Perhaps I am a bit confused, to you is there increased sharpness and contrast with the 56 over the 42 when viewing objects out/about, but when viewing the USAF chart, there is none?

Andy W.

The difference in sharpness and contrast is noticeable on the USAF chart, just like in the field, but I can't actually resolve the next smallest group of line pairs with the 8x56. It's similar to looking at the photos in the link from the proper distance, only less obvious because the 8x42 FL has lower aberrations than than the Habicht.

I should mention that tripod mounting makes these small differences much easier to see.

Henry

Henry,

Got it, thanks for the time you have spent on the research very much appreciated. By the way, viewing last night the stars, what a great experience, it is easier than the 10X56 FL(was there also by another viewer) to hold steady, and there was some astigmatism at the edges, but a great glass to survey the sky. The leica 10X50 HD+ was fun also with 6.7 degree FOV.

Andy W.

dries1 said:

While looking at small structure, i.e. pine needles, small scale wood bark at distance, and I compare the 8X42FL and 8X56FL, I get better resolution with the 8X56 than the 8X42. I see more detail of these structures.

Andy W.

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Andy,

Your stated "greater detail view" in the larger objective 8X56 brings up an interesting thought. Out of curiosity, could someone measure the objective mm spacing for a given IPD to find if it is equal\different to the ocular spacing? I'd be curious to hear about the same measurement results with the SLC 8X56.

If there is a difference, could a large objective roofs' greater stereopsis effect, related to a wider spacing of the objectives (like my El 10X50 SV's +9mm difference from its IPD setting) realistically offer visual advantages similar to what has been described by several members in this thread?

Ted

When the 8x56 FL IPD is set for 65mm the objective spacing is 79mm, and yes, that does produce a little extra stereopsis and a noticeable but slight illusion of a smaller image scale at close range compared to straight through roofs.

henry link said:

When the 8x56 FL IPD is set for 65mm the objective spacing is 79mm, and yes, that does produce a little extra stereopsis and a noticeable but slight illusion of a smaller image scale at close range compared to straight through roofs.

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Thanks Henry! Would this possibly contribute to some of the "positive impressions" observers notice with larger objective optics? Or is it mostly based on reduced FOV aberrations observed with daytime constricted pupils?

Much appreciation for your contribution, and many other member inputs to this thread! :t:

Ted

Like Henry, I've done a lot of side by side comparisons of different binoculars, estimated both full objective and stopped down resolutions value, and noted significant variation in perceived image sharpness

Henry mentioned my visual acuity was a bit better than his, but l still found my magnified and unmagnified acuities often corresponded exactly, meaning the effective resolution is eyesight limited (though there have been a number of notable occasions where the binocular was limiting). Where where my eyesight is the limiting gactor I still find clear differences in apparent sharpness which appears to correspond exactly to the stopped down resolution.

I should point out these distinctions will be increasingly difficult to detect as the gap between the instument and the eye's effective resolution increase and it probably helps to have well developed perceptive skills too.

I've bench tested something over 20 different binoculars with objective diameters between 30mm and 56mm and I have found absolutely no relationship between objective size or exit pupil diameter and effective optical performance. The best I've found for both effective resolution and perceived sharpness were an 8x32 and a 12x50. My worst binocular by some margin was a $30 10x42, and as far as I recall, when boosted, it wasn't anything like as bad as Henry's image for the 8x30 Habicht. I think there might have been a technical issue with that photo.

I'm not as young as I once was, and I'm more dependant on good light conditions to judge optical quality than I used to be. Thinking back over various visits to Birdfair and different retailers, I've probably looked at 400-500 different binoculars when my eyesight was firing on all cylinders. They would have ranged from 8x20s through to 20x80s. I'd guess perhaps 20 or so really wowed me at the time, and I suspect might have matched the Dawes limit. That means they would have been essentially aberration free stopped down. That would have included some alphas, but some mid range and at least three budget binoculars would make that list. Rather more, including some from the big three companies, have been clearly optically limiting.

I should point out that resolution by no means the only factor to control image quality, and others may have different priorities.

David

PS. I should have mentioned that I have tried the 8x30 Habicht on three occasions. My opinion at the time was that was that the resolutions of those samples were good, possibly around 125-130/D, but definitely short of the Dawes limit. In my opinion they were all further impaired by a diffuse stray light issue.

Troubador said:

I was grasping at straws really, trying to come up with a word that might capture the nature of the quality of the view through the FL 8x56s.

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Would it help to describe what a view looks like that doesn't have this quality?

henry link said:

It shows pretty well how a low aberration image can look sharper and higher contrast than a higher aberration image without actually resolving any smaller quantifiable detail at the limit of eyesight acuity.

Click to expand...

That's very helpful, and I didn't pick up on it when I preiously read that post. Details can look sharper without actually seeing any finer detail. Andy (post 201), which do you think you're seeing with your 8x56?

tenex said:

Would it help to describe what a view looks like that doesn't have this quality?

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Good idea, thanks for suggesting. The area around where I live isn't conducive to this being littered with houses and roads but in about 3 weeks we will be in the west of Scotland and I will give this a try there.
Thanks again.

Lee

To add my own experience... After five weeks with this 10x56 SLC now, I can say that its view is modestly brighter even in full daylight than the 10x32 UVHD+ that's my everyday bino, and this is a nice effect. It could involve AK prisms over SP, and possibly different optimization of coatings, more than objective size (given my contracted pupil). It strikes me as very similar to the improvement in the UV over my previous 10x32 BN, which I can still borrow for testing, with its silver-coated mirrors: better overall transmission.

In large shadow areas or dimmer overall light, of course, the SLC 56 wins handily. But I'm not sure I can detect any other optical advantage due to its large objectives in bright daylight. If anything, the UV 32 does a bit better at Leica's famous microcontrast. Otherwise any differences in color, contrast, etc are very minor, and rendering of detail seems entirely comparable. To my eyes, both glasses are simply excellent.

New member here and another appreciator of large objective binoculars for daytime nature use. My main bins I use are Zeiss Victory 8x56 FL. I find the view relaxed with their very large sweet spot that's very crisp and sharp. I find their heft an aid in keeping them shake free and they balance just fine in my mitts. I wouldn't want to carry them up a mountainside but for all day use with a harness I find no strain or need to reach out to the local chiropractor for adjustments (Yet . ) I guess it's what we get used to. I am quite curious to try out a pair of Swaro SLC 8x56 and compare to my big FL's.

Markus