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Thread: 8x40 vs 7x50

  1. #11
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    Good point, the problem we face is we can check binos in the shop during the day, but we can't test them at night. We can read articles on the web & do our best to get an informed view but still end up with something not as good for us as it could be. 8x40s are still a good choice though. I'm at a loss now to explain exit pupil issues when we get older. I suppose it highlights the benefits of joining a club.

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    ...........

  3. #13
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    Hello Tony,

    thanks for the interesting test report on the binos.

    I have had the Olympus 8x40 Porro prism bino some time ago, it was in fact one of the best 8x40s I have had in my hands.

    Regarding the low magnification of 7x, the best choice according to my experience would be, either a very wide field of view bino (definitely at least 9deg), or a high-end bino like Leica, with the enourmous high transmittance and contrast. Those both make sense whenefer you have clear skies, e.g. you can easily recognize the Great Rift in the Cygnus Milky Way, in summer.

    Regarding 10x50, check the Williams Optics, they have introduced APO ED corrected binos on the market. They may have individual focussing, not actually comfortable on terrestrial viewing.

    Should you try higher, 10.5x70 and 11x70 are great things, if your budget allows for nebular filters. However, the weight of these binos.

    Lots of people prefer 12x50 on suburban skies, because of high contrast due to the exit pupil of 4mm.

    Regarding your exit pupil, do not worry. I am 66, and doing perfectly well with the 10.5x70. I insert the narrow band OIII filters in the EP barrells, and then keep watching how the dim emission nebulas are coming up when my eye pupils open because of missing the sky glow background.

    Best

    JG
    Binoculars: Leica Ultravid 7x42, 8x42HD; Swarovski EL 8.5x42 Swarovision; Nikon 10x70 Astroluxe; Docter Nobilem 7x50 Porro; Jenoptem 7x50W, 10x50W; BA8: 10.5x70, 15x85; 25x100FB, AsahiPentax 8x40, Refractors: Sky-Watcher 150mm/750mm; Leica APO Televid 82mm (25x-50x WW ASPH); EPs:Baader Classic Orthos; Fujiyama ortho, Leica B WW, ultrawide zoom ASPH, Periplan GF, HC Plan S, L; DOCTER UWA; Wild UW mil; Tele Vue Delos, Nagler Zoom, Plössls; Swarovski SW; Pentax XW; ZEISS diascope B WW T*, Carl Zeiss E-Pl; Hensoldt mil; Filters: Astrodon, Astronomik, Baader (CCD), TS;
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    Hello Tony,

    ther is one more remark on what is better, 7x50 or 8x40.

    there are two issues to be considered
    1) Lots of people take a figure of merit, to compare the visual brightness of nebulas, namely:
    exit pupil squared times the magnification. It may be no physical reason for it, but this formula works well:
    7x50 gives 357
    8x40 gives 200
    2) What finally matters is the contrast and the transmissivity of the bino.

    I have had on trial the Leicas Ultravid 7x42 and 8x42 by daylight. Even if both have the same multicoating technology, the 7x42 was brighter even by daylight, due to another design of the eyepieces. I do not think, that my eyes open beyond 5mm during daylight.

    Wishing you best choice

    JG
    Binoculars: Leica Ultravid 7x42, 8x42HD; Swarovski EL 8.5x42 Swarovision; Nikon 10x70 Astroluxe; Docter Nobilem 7x50 Porro; Jenoptem 7x50W, 10x50W; BA8: 10.5x70, 15x85; 25x100FB, AsahiPentax 8x40, Refractors: Sky-Watcher 150mm/750mm; Leica APO Televid 82mm (25x-50x WW ASPH); EPs:Baader Classic Orthos; Fujiyama ortho, Leica B WW, ultrawide zoom ASPH, Periplan GF, HC Plan S, L; DOCTER UWA; Wild UW mil; Tele Vue Delos, Nagler Zoom, Plössls; Swarovski SW; Pentax XW; ZEISS diascope B WW T*, Carl Zeiss E-Pl; Hensoldt mil; Filters: Astrodon, Astronomik, Baader (CCD), TS;
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    Hi JG,
    Both are excellent replies, thanks. I now own the 7x50 Action EX and have sold the 8x40's.
    The Olympus 8x40's are great because they're so light and give the same 8.2 degrees FOV as the Nikons.
    Your formula EP squared x magnification is very interesting, where did that come from? It certainly makes sense to work out a formula for getting binocs that are the most useable, though it wouldn't take into account the variation of quality from manufacturer to manufacturer.
    Regarding the Leica binocs, they look great, I would normally associate roof prism bins with a narrower field of view compared to porros. 8 degrees is very impressive! Do they or did they maintain image sharpness across the whole field of view?
    Regarding transmissivity I guess you're talking light transmission or brightness? Nikon rate the brightness of their 8x40s at 25, the same as their 10x50s. Leica rate their 7x42s at 36 and their 8x42s at 28. But the 7x50 Nikons come in at a brightness of 50, which I would suspect would be similar to other porro manufacturers of this type binocs. The trade off is the narrower FOV at 6.5 degrees.You pay your money and you take your choice. The cost of the Leicas would probably give my wife sleepless nights too! Perhaps as you're in Germany the Leicas may be somewhat cheaper for you, when I was in the UK I noticed Japanese imports to the EU sseemed to attract more import taxes.

    Good luck and clear nights to you.

    T.

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    Quote Originally Posted by tony884 View Post
    Hi JG,
    Your formula EP squared x magnification is very interesting, where did that come from?
    T.
    Hello Tony,

    I can't remember exactly the origin of the "(EPsquared)*Magnification" formula. It has been posted in Cloudy Nights, or elsewhere. However, my experience would tell me, the brightnes of faint DSOs increases with magnification, and the light flux pulled into the eyes increases with the EPdiameter squared.

    This is one issue.
    The other one has to do with contrast and brightness. High-end glas materials, and terribly expensive multicoatings are necessary to manufacture a good binocular. That makes the Leica binos so expensive. The Leica Ultravid binos achieve the transmissivity, that you'll experience as brightness, well above 96%, the 7x42 is possibly 98%. Just to remember, binos with the transmissivity of 80% are still in use for astronomy, and will be ragarded as fairly good. Unfortunately, other manufacturers beyond Leica and Zeiss do not give this number.

    The other number you have mentioned, may be the twilight factor:

    STEINER-Optik | Binocular | Twilight Factor | Binocular Terminology | Binoculars

    Back to Leica and to those sleepless nights. All Leicas and Zeiss are basically birding binos, some of them usable during twilight. They are nice to have, but they may become must to have only when you can get them with some price reduction. This was my case, but with sleepless nights anyway.

    Last but not least, 40 years old Zeiss binos are offered for prices around 1,000 USD. I'd say, the high-end Leicas and Zeiss won't loose their value fast.

    Best

    JG
    Binoculars: Leica Ultravid 7x42, 8x42HD; Swarovski EL 8.5x42 Swarovision; Nikon 10x70 Astroluxe; Docter Nobilem 7x50 Porro; Jenoptem 7x50W, 10x50W; BA8: 10.5x70, 15x85; 25x100FB, AsahiPentax 8x40, Refractors: Sky-Watcher 150mm/750mm; Leica APO Televid 82mm (25x-50x WW ASPH); EPs:Baader Classic Orthos; Fujiyama ortho, Leica B WW, ultrawide zoom ASPH, Periplan GF, HC Plan S, L; DOCTER UWA; Wild UW mil; Tele Vue Delos, Nagler Zoom, Plössls; Swarovski SW; Pentax XW; ZEISS diascope B WW T*, Carl Zeiss E-Pl; Hensoldt mil; Filters: Astrodon, Astronomik, Baader (CCD), TS;
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    Are you an OLD guy or a YOUNG person?

    Old = 10x50mm with about a 5mm exit pupil-- for older folks.

    Young- ? Then the 7x50mm will yield a brighter image since it has a larger exit pupil.

    Assuming similar good optics.
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    Hello Joe,

    how are you doing with your new 25x100?

    Looking forward to your reports

    JG
    Binoculars: Leica Ultravid 7x42, 8x42HD; Swarovski EL 8.5x42 Swarovision; Nikon 10x70 Astroluxe; Docter Nobilem 7x50 Porro; Jenoptem 7x50W, 10x50W; BA8: 10.5x70, 15x85; 25x100FB, AsahiPentax 8x40, Refractors: Sky-Watcher 150mm/750mm; Leica APO Televid 82mm (25x-50x WW ASPH); EPs:Baader Classic Orthos; Fujiyama ortho, Leica B WW, ultrawide zoom ASPH, Periplan GF, HC Plan S, L; DOCTER UWA; Wild UW mil; Tele Vue Delos, Nagler Zoom, Plössls; Swarovski SW; Pentax XW; ZEISS diascope B WW T*, Carl Zeiss E-Pl; Hensoldt mil; Filters: Astrodon, Astronomik, Baader (CCD), TS;
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    Tony thanks for a great post on the Nikon Action series

    I recently got the 7X50 and I think they are a great balance of wide-field views, steady views, and price (for me in Australia at least as other binoculars are outrageously priced and many are junk).
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    Yes thanks Tony for your timely report as I am just now looking for my 1st pair of binoculars

 

 
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