The thickness of a lens is directly proportional to its diameter. A smaller diameter, like that in a 40mm SFL binocular, means the lens will be thinner overall than the 42mm in an SF binocular and substantially lighter. A bigger objective lens is always thicker to support its weight, even in a telescope.
Thanks Dennis, That helps.
Interesting! Now it just sounds like marketing. The lenses are thinner because they're smaller lenses. i.e., you're better off ignoring the thin/thick lens talk
I get the forum is full of great technical optics conversations. Am not aware of any discussion of this specific thing, that is thickness and the implications, to optical performance, durability, weight and cost.
Yea well that was sorta the point. I was hoping this wasn't just advertising shorthand, which it indeed appears to be. (I make a distinction between marketing and advertising, selling).Interesting! Now it just sounds like marketing. The lenses are thinner because they're smaller lenses. i.e., you're better off ignoring the thin/thick lens talk
Where on earth did you get this supposed quote? I can't find it with Google but it's ridiculous nonsense. Try to visualize a 40" objective 23 inches thick? The correct figures for center and edge of the crown lens are 2.5" and 3/4". (link)
This is false, and the added psuedo-accuracy of "directly" is especially offensive. The thickness of a lens depends on its radius of curvature, i.e. the optical design.
Why do you pontificate on subjects you don't remotely understand? This is completely backwards. The refractive index of a particular glass type determines the speed of light traveling through it, which is the same in any lens made of that glass regardless of thickness. Beyond that, the amount of refraction depends on the angle of incidence, determined by the radius of curvature. And that in turn determines the thickness of the lens, so for a given glass and diameter, a lens of shorter focal length will be just a bit thicker.
This marketingspeak is not talking about advances in optical design, merely the choice to offer more compact 30 and 40mm models instead of 32 and 42.
Clearly Dennis is using AI to write the bulk of his posts these days. And AI hallucinates facts, as you likely know.
Where on earth did you get this supposed quote? I can't find it with Google, but it's ridiculous nonsense. Try to visualize a 40" objective, 23 inches thick? The correct figures for center and edge of the crown lens are 2.5" and 3/4". (link)
Why do you pontificate on subjects you don't remotely understand? This is completely backwards. The refractive index of a particular glass type determines the speed of light traveling through it, which is the same in any lens made of that glass regardless of thickness. Beyond that, the amount of refraction depends on the angle of incidence, determined by the radius of curvature. And that in turn determines the thickness of the lens, so for a given glass and diameter, a lens of shorter focal length will be just a bit thicker.
Tenex, every once in awhile you can offend. This is one of those. Why are you lumping my questions with Dennis replies. It’s you and he thatre going at it. Please stop this.
This idea is completely false. You really have no clue what's going on here, which is cause and which effect, or why. Not even after reading what I wrote, if you did.
Now that you mention it, I was going to dissect some of them too but edited that out, no idea why really. In any case you are at least feeding and encouraging his foolishness. This thread must have run its course.
Thicker convex lenses in a binocular will refract or bend light more because they have more curvature, which leads to a greater change in the direction of the light rays as they pass through it. The SFL has thinner lenses, so they naturally have less curvature and will refract light less, but Zeiss probably uses glass with a higher refractive index to make up for the difference in refractive properties. That is probably partly how a SFL achieves it lighter weight and more compact size. That and spacing the lenses closer together, so the body of the binocular is smaller.
