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7X42 format.

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#1 paulsky

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Posted 21 April 2019 - 10:30 AM

Hello,
I have been able to use some binocular 7x50 as an astronomical observation instrument, and the truth is that it has given me good ... but only in dark skies, maybe it's the 7mm of exit pupil, in suburban skies the bottom of the sky has always been too much clear, losing contrast the images provided. I would like to ask you if some of you have been able to compare them with the 7X42 format ... and the advantages, if any, they have. I imagine that the biggest opening, of 50mm will always have an advantage over 42mm, maybe the format 7x42 has a greater AFOV, less weight ..., maybe these are some advantages in favor of the 7X42 format.Has anyone seen superiority in some 7X42 vs 7X50 ...?
I would like to hear your opinions on this topic.

Thanks in advance.
Paul

 



#2 Rich V.

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Posted 21 April 2019 - 11:24 AM

How wide do your eyes dilate at night?  Can you really use a 7x50's 7mm exit pupil?  If no more than 6mm, then a 7x42 will deliver the same brightness as a 7x50 to your eyes but you'll have the benefit of a more compact bino with very likely a wider FOV.

 

Rich


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#3 SMark

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Posted 21 April 2019 - 12:32 PM

I did my own "scientific" coolnod.gif experiment awhile back using 7x35 / 7x42 / 7x50 binoculars under my suburban Atlanta night skies. In an effort to make it fair, I used relatively high quality, standard field binoculars in all cases. My 7x42 was an armored Swarovski Habicht made within the last 20 years or so. My purpose was to make note of what the incremental change in exit pupil was really offering me. In the end, I found myself preferring the 7x50 because of the brighter images and increased detail. 


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#4 Erik Bakker

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Posted 21 April 2019 - 01:51 PM

Having had the Zeiss 7x50 B/GA and later the Zeiss Victory FL 7x42 for many years, here's my take.

 

The FL 7x42 was showing me views I enjoyed much more than the 7x50 B/GA. And I found it easier to focus (because of it's center focus) with more eye relief and better adjustable eye cups. At almost half the weight, it was also much more convenient to carry and hold. 3D effect goes to the 7x50 porro, but the 7x42 Victory FL was still quite OK in this respect. Compared to 8x42's, big low surface brightness objects are easier to find and observe.

 

7x is a wonderful lowish magnification, with generally smallish apparent and -true fields. There are very few notable exceptions, approaching 60 degrees AFOV. All in the 42mm roof variety from premium makers for a premium price: Zeiss, Nikon and Leica come to mind. 

These exceptions open up the skies in a grand way. Offering, bright, wide, stable involving views in a hand held instrument. But in the end I generally prefer 8x wide AFOV binoculars to differentiate deep sky objects from stars and see more detail.

 

If I wanted 7x binoculars gain, I would choose one of the scarce 7x42 high end roofs. Lightweight, wide and involving views. Edge of field is not very sharp in the few models available up to this date. 

 

Once I got my Nikon 8x30 EII, my Zeiss FL 7x42 no longer saw any significant use. Perhaps because I also have an FL 10x56 as well, from the moment I got it my preferred hand held instrument once the night falls.

 

By itself though and as an only instrument, a top quality 7x42 wide field roof is a wonderful instrument.


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#5 MartinPond

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Posted 21 April 2019 - 07:07 PM

I think the extra brightness and detail some see with larger exit pupils

 is  the excess exit pupil making the eyepieces far easier to place over the eyes.

One assumption behind the 'wasted pupil' doctrine is that your eyes and ipd are always

 100% perfect.  Impossible.   If one of your eyes has to jog a bit to catch a full EP,

  your eyes don't properly align and combine...it's a change in direction after all.

A few 'wasted' mm of exit pupil could be just what's needed to fit.


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#6 harbinjer

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Posted 21 April 2019 - 08:36 PM

I think the extra brightness and detail some see with larger exit pupils

 is  the excess exit pupil making the eyepieces far easier to place over the eyes.

One assumption behind the 'wasted pupil' doctrine is that your eyes and ipd are always

 100% perfect.  Impossible.   If one of your eyes has to jog a bit to catch a full EP,

  your eyes don't properly align and combine...it's a change in direction after all.

A few 'wasted' mm of exit pupil could be just what's needed to fit.

I completely agree with Martin: He says it better than I could. Large exit pupils(and especially paired with long eye relief) feel very relaxed, comfortable, and luxurious.

 

Regarding 7x42 and 7x50; my 7x42 is the Meade Montana, with a 8* FOV and field flatteners, which is the biggest difference that I see, and it is noticeably more immersive. It doesn't seem to have better detail or contrast in the city. With light pollution, I really prefer 8x40 or 10x50 with their smaller exist pupils and higher magnification. But I haven't done an a/b/c comparison like SMark. Also I don't think I have binoculars of similar enough make quality to compare their size as opposed to optical quality in their make.


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#7 Jon Isaacs

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Posted 24 April 2019 - 09:38 AM

I completely agree with Martin: He says it better than I could. Large exit pupils(and especially paired with long eye relief) feel very relaxed, comfortable, and luxurious.

 

Regarding 7x42 and 7x50; my 7x42 is the Meade Montana, with a 8* FOV and field flatteners, which is the biggest difference that I see, and it is noticeably more immersive. It doesn't seem to have better detail or contrast in the city. With light pollution, I really prefer 8x40 or 10x50 with their smaller exist pupils and higher magnification. But I haven't done an a/b/c comparison like SMark. Also I don't think I have binoculars of similar enough make quality to compare their size as opposed to optical quality in their make.

 

I have a pair of 7x42 Meade Montana's. I like em.. A few thoughts:

 

- 7x50s are porros, 7x42s are roofs.. at least as far as know..  This is the big difference.. 1 mm exit pupil, not so much.  Roofs are more versatile, birding etc, more compact.

 

- Inexpensive and/or older 7x50s maybe be closer to 7x42s.. best to measure. The Montana's measure full aperture.

 

- It is only when the exit pupil is equal to your dilated pupil that matching is difficult. If your dilated pupil is larger than the exit pupil the same advantage exists..

 

- I do see more in my 7x50s than the 7x42s regardless of whether the skies are light polluted or not but generally I see more in 10x50s than either of those.

 

Jon



#8 Mark9473

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Posted 24 April 2019 - 11:18 AM

Put two 42mm cardboard aperture masks on your 7x50 and find out for yourself.



#9 25585

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Posted 03 May 2019 - 05:37 AM

I think the extra brightness and detail some see with larger exit pupils

 is  the excess exit pupil making the eyepieces far easier to place over the eyes.

One assumption behind the 'wasted pupil' doctrine is that your eyes and ipd are always

 100% perfect.  Impossible.   If one of your eyes has to jog a bit to catch a full EP,

  your eyes don't properly align and combine...it's a change in direction after all.

A few 'wasted' mm of exit pupil could be just what's needed to fit.

I find exactly that.



#10 Binojunky

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Posted 03 May 2019 - 10:05 AM

Quality makes a difference also, a good or premium 7x42 roof is far preferable to a cheap or low cost 7x50, D.


Edited by Binojunky, 03 May 2019 - 10:06 AM.



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