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question about objective lens size

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question about objective lens size

Postby Nate on Sun Apr 05, 2009 1:25 am

I'm not a complete novice to optics, but I certainly don't claim to be an expert either. Recently, I read this on one optics company's website...

"All else being equal, a larger objective lens will always deliver more detail than a smaller one regardless of the magnification."

I was aware that larger objective lenses could affect how bright an image it due to exit pupil, but I don't believe I'd heard that larger lenses necessarily made images sharper. Is that statement true?
Nate
 

Re: question about objective lens size

Postby Jne_K on Mon Apr 06, 2009 6:40 am

Yes, it is true in terms of resolution - the ability to separate two very closely spaced objects and show them as two objects instead of one. Resolution is directly related to objective size. The larger the objective, the closer of two objects that can be resolved. Resolution can be expressed by one of several optical formulas. In amateur astronomy, it has practical significance when trying to separate two very closely spaced stars. In a binocular, you will notice the difference in terms of overall sharpness. Keep in mind that this applies only to lenses of equal quality. Lens quality is a siginificant factor as well when it comes to resolution.
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Re: question about objective lens size

Postby Nate on Wed Apr 08, 2009 7:54 pm

Thanks for your input. I realize it may be hard to quantify, but supposing I used two binoculars from the same line but one was a 42x8 vs a 32x8, (and I used them in a bright enough setting that exit pupil wouldn't come into play) would the difference in sharpness be very noticeable?
Nate
 

Re: question about objective lens size

Postby Jne_K on Thu Apr 09, 2009 5:42 am

Hi

No, assuming equal lens quality, there would only be a small difference but a critical eye would notice it. However, the only way to assume equal quality is to stay with the same model or at least the same general price. Qulaity is a more important factor when comparing binos at widely different prices.
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