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Why 42mm? (1 Viewer)

ailevin

Well-known member
Is there some historical reason we have 8x42 or 10x42 as "standard?" I get 7x50, 7x42, 7x35 with exit pupils of 7mm, 6mm, 5mm or 10x50, 8x40, 6x30 all with 5mm exit pupil.

Alan
 

Vespobuteo

Well-known member
Is there some historical reason we have 8x42 or 10x42 as "standard?" I get 7x50, 7x42, 7x35 with exit pupils of 7mm, 6mm, 5mm or 10x50, 8x40, 6x30 all with 5mm exit pupil.

Alan

10x50, 10x40, 9x35 were probably the most common sizes for birding 30-40 years ago.

Not sure who was first with the "modern" 8/10x42mm, Leica BA (later BN) around 1990 perhaps?

Leitz (Leica) made a 7x42 Trinovid already back in 1958.

https://www.l-camera-forum.com/leica-wiki.en/index.php/Roof-Prism_Leica_Binoculars

The latest "size-revolution" is probably the HT 8/10x54. Smaller packages and EP than 56mm but compensated with HT glass with high transmission.

I think better glass/coatings and larger eye pieces have made smaller bins (25-32mm) more usable than they used to be. The eye pupil might still demand a bit larger EP to be optimal in low light. But many birders seem to be fine with 8x32 bins these days.
 
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ceasar

Well-known member
In a word, practicality.

42mm bins have the best potential compromises of weight and power for the general public. Prism weight is manageable. With 42mm @ f4 it is easy to make varieties of eye pieces for 7x, 8x, 10x (and even 12x )with long enough eye relief and a variety of FOVs.
 
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Foss

Well-known member
Great question, Alan, and already some great answers. I knew Leitz (Leica) 7x42 Trinovid had been around a long time, but had no idea it dated back to 1958.
 

ailevin

Well-known member
I like Temmie's analysis. Vespobuteo's link to Leica history is interesting, and it supports my anecdotal sense as viewed from the astronomy community that something changed in the late 20th century. My theory is that in the days of the Porro, manufacturers were trying to use the same sized prisms in multiple models if possible because of the optical and mechanical issues of mounting and adjusting. I have seen older 7x50 and 10x70 that have that prism housing resemblance. At any rate, except for compacts I mostly only saw binoculars with pretty close to integer exit pupils, the most popular being 7mm and 5mm with some slightly less bulky 6mm glasses or occasional higher power 4mm glasses. I wonder if it is the Spinal Tap phenomenon. Instead of an amp with a volume knob that goes up to 11 instead of 10 we have a 42mm binocular with a mag 8 instead of 7. And then we have the Swaro 8.5x42, which ups the magnification just a smidge and brings the exit pupil back closer to 5mm.

I am not claiming there is an optimum or a perfect glass that everyone should use. I am just curious about how our current market offerings evolved. Because exit pupil is one of the first things I think about with a binocular, I wondered how we got away from round numbers. OTH, I know that many consumers, especially newbies tend to be most attracted by and impressed with magnification. Maybe someone from the optical business end of things has some insight from that side?

Thanks,
Alan
 

maico

Well-known member
The pre-war Hensoldt Wetzlar designs came in both 7x56 and 8x56 Nacht-Dialyt which again is a nice round number for the exit pupil of 8mm and 7mm.
So were the Hensoldts 6x42, 7x42, 8x32 and 10x50 variants but the 7x50 and 8x30 weren't !

( photos inc. Hensoldt 7x50 Abbe-Koenig roof prism from WPG collection https://www.flickr.com/photos/binocwpg/)
 

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Foss

Well-known member
Here's a set of early Hensoldt roofers I recently "deaccessioned" out of my collection. Nice optics for the era. I can see how birders in the early 1900s would be attracted to them 6x26 (the 26 is approx).
 

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OPTIC_NUT

Well-known member
I think 30-->32 and 40-->42 were just a way to set things apart for marketing,
especially for the roof models as they built up.
 

Binastro

Well-known member
Of all the commonly available binocular sizes up to 60mm aperture, 42 is the prettiest in binary.
101010.
The robots that control us know this :)

21 is slightly pretty.
10101.

As is 32.
100000.
 

quincy88

Well-known member
Cool thread Alan,

Do you guys think that the little ones will ever be so homogenous? It doesn't seem like the full-size compacts are as far along in this process. I mean, there are a lot of 32 mm and a lot of 30 mm still out there on the market. Do you think that one day it will be almost exclusively 32 mm?

Maybe it is all marketing - a way to set apart a manufacturer's top-of-the-line from their mid-range. Swarovski has 30 mm CLs and 32 mm ELs. Nikon has (or had?) 32 mm EDGs and 30 mm Monarchs.
Alternatively, though, Leica has 32 mm Ultravids and Trinovids. Same with Zeiss, 32 mm Victorys and Conquests.

Are the differences between 30 mm and 32 mm enough to justify both? Does anybody own and use both for different situations? I get that the 30s will be slightly smaller and lighter and the 32s will be slightly brighter. Are those differences big enough to warrant both models?

-as you were, q
 

St. Elmo

Well-known member
I seem to recall a Better View Desired article on why 42mm was the best (or, perhaps, I read it on the back of a box of Rice Krispies). In any case, someone did analyze this matter within the last 10 years or so. Was it you, Dr. van Ginkel?
 
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ailevin

Well-known member
Cool thread Alan,

Do you guys think that the little ones will ever be so homogenous? It doesn't seem like the full-size compacts are as far along in this process. I mean, there are a lot of 32 mm and a lot of 30 mm still out there on the market. Do you think that one day it will be almost exclusively 32 mm?

Maybe it is all marketing - a way to set apart a manufacturer's top-of-the-line from their mid-range. Swarovski has 30 mm CLs and 32 mm ELs. Nikon has (or had?) 32 mm EDGs and 30 mm Monarchs.
Alternatively, though, Leica has 32 mm Ultravids and Trinovids. Same with Zeiss, 32 mm Victorys and Conquests.

Are the differences between 30 mm and 32 mm enough to justify both? Does anybody own and use both for different situations? I get that the 30s will be slightly smaller and lighter and the 32s will be slightly brighter. Are those differences big enough to warrant both models?

-as you were, q

I'm not sure if there is an official set of categories, but I think of full-size as 40mm-50mm, mid-size as 32mm-35mm, and compact as 20mm-30mm. However there is overlap in size (bulk) and weight at the boundaries between these categories. Reduced size/weight are the motivators for going to a smaller objective. Improved optical performance and handling are the motivators for going larger. Once again there are overlaps between categories.

32mm vs. 30mm is a small factor, and likely not a determining factor in how a binocular performs. I've gone from 8x32 to 8x30 to 8x25 as my preferred mid-size/compact binocular. And this movement to smaller objective was driven more by improved view than difference in size. This has more to do with the characteristics of particular binoculars, not so much 32 vs. 30 vs. 25. If I am concerned about low light or want best performance under all conditions I use an 8x42 or 9x45 instead.

Judging from folks who post here, I had gotten the impression that there had been a move toward smaller objectives mostly 42 to 32. OTH, data posted here from manufacturers and retailers indicates that 42 is much more popular in the marketplace. The fact that there is less variation around 42mm size may be either an economy of scale thing or a perception by manufacturer that 42 is what sells best. It's interesting that the newest models Zeiss and Swaro are 25 and 30 like they are fishing around to see what sells best in that market.

Alan
 

dries1

Member
If one thinks about it, the 8X42 and 10X42 format is the most versatile, lighter than the 50s and easier for eye placement and cover a wider range of viewing conditions (low light) than 30-32. Why they changed from 40 to 42, I have no idea.

Andy W.
 

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