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7x50 brightness

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Old Tuesday 4th August 2015, 08:03   #1
Jake21
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7x50 brightness

Do you guys think that 7x50 generaly has better brightness then 8x42?
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Old Tuesday 4th August 2015, 08:51   #2
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Jake,

Not a straight forward question to answer. Obviously a 7.1mm exit pupil is bigger than a 4.25mm so potentially more use in low light., but we are getting into moonlight levels not normal birding. How much our pupils dilate changes with age and the average 60 year old probably won't benefit from more than 5.25mm anyway, but it is very variable.

Now for the fly in the ointment. Brightness is a perception, your eyes are not light meters. In fact they are very bad at judging light levels as you pupils continually adjust to keep the level of light reaching your retina constant. If you were to look down to pick up another binocular you pupil would change and no accurate comparison is possible. However people report differences in binocular brightness all the time here. Your brain reads the clues in colour balance and contrast and guesses whether a scene is brighter or dimmer but but that has almost nothing to do with light levels in this context. The coatings on a binocular's lens and prisms act as optical filters and change your perception. Bluer biased binoculars are often described as brighter than warmer biased models for example. That has nothing much to do with the transmission at 550nm transmission value which is the wavelength of maximum daylight sensitivity.

Hope that wasn't too confusing.

David

Last edited by typo : Tuesday 4th August 2015 at 09:50.
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Old Tuesday 4th August 2015, 09:32   #3
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Jake,

I just realised your first interest is astronomy. Big exit pupil are good for feint objects but the brighter ones will be sharper with a smaller exit pupil. Our visual acuity decreases as our pupils dilate. A couple of percent difference in transmission is of little consequence for astronomy I suspect, but our peak night time sensitivity is 505nm.

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Old Tuesday 4th August 2015, 14:19   #4
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Hi Jake,
Can you see the Milky Way with your unaided eyes from where you observe the sky at night?
If you can and you are fairly young then the 750 is probably beneficial for you.

In the 1950s a Belgian Observer using a 750 binocular was able to trace out the Andromeda nebula, M 31 to 5 on its long axis.

The military used 1080 binoculars as young observers, around 19 or 20 years old, could make use of these.
Also as they were used at sea even with smaller pupils they were still within the exit pupil of the binoculars.
In fact young people can have pupils up to 9 mm across. I think even when sober.
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Old Tuesday 4th August 2015, 15:18   #5
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Quote:
Originally Posted by Jake21 View Post
Do you guys think that 7x50 generaly has better brightness then 8x42?
If you are over 30 probably not. The 7x50 will give you a bigger exit pupil which makes eye placement easier but if you compare the two side by side for birding you would choose the 8x42.
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Old Tuesday 4th August 2015, 15:48   #6
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Here you go, ask no more. This is it. Best bang for your buck. Lightest quality 7x50 out there. Good color and contrast, nice ergonomics. Big sweet spot. The oversized eyecups are my only beef, but I have deep-set eyes, they may work fine for you. For stargazing, even your heartbeat causes stars to become bouncing balls, so for handheld binocular stargazing, 7x reduces shakes.

Even if your pupils only open to 5mm, I think you will still find the view of the night sky more satisfying through these than comparably priced 8x42s.

7x50_ZCF_Foresta_Binocular

Is that price within your budget?

Brock

Last edited by brocknroller : Tuesday 4th August 2015 at 16:13.
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Old Tuesday 4th August 2015, 17:47   #7
Jake21
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Originally Posted by brocknroller View Post
Here you go, ask no more. This is it. Best bang for your buck. Lightest quality 7x50 out there. Good color and contrast, nice ergonomics. Big sweet spot. The oversized eyecups are my only beef, but I have deep-set eyes, they may work fine for you. For stargazing, even your heartbeat causes stars to become bouncing balls, so for handheld binocular stargazing, 7x reduces shakes.

Even if your pupils only open to 5mm, I think you will still find the view of the night sky more satisfying through these than comparably priced 8x42s.

7x50_ZCF_Foresta_Binocular

Is that price within your budget?

Brock


Wow.. I will definitely buy this in the future.. its light, water proof, and has a better FOV then the bios I currently own. Thank you for your recommendation!
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Old Wednesday 5th August 2015, 04:50   #8
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Wow.. I will definitely buy this in the future.. its light, water proof, and has a better FOV then the bios I currently own. Thank you for your recommendation!
Thank Bryce, too, he gave them to me. Frank D. had praises for the Forestas, but I thought the 7.1 FOV would be too limited (particularly after owning a 10* 7x50 Celestron Nova), but the EPs are so huge and you can move your eyes around the field of view.

The objectives have triplet lenses, the rubber eyecups have click stop metal frames underneath them like the $1000+ Nikon HGLs, and the AR coatings produce VG color saturation and contrast. The rounded prism housing are comfortable to hold and they are flat on the bottom so they provide good thumb support.

If anything ever goes wrong with them, Vixen will repair or replace them for $25 no questions asked.

Brock
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Old Thursday 6th August 2015, 17:19   #9
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Originally Posted by brocknroller View Post
7x50_ZCF_Foresta_Binocular

Is that price within your budget?

Brock
And if it's not, you might want to get a pair of old soviet ZOMZ 7x50. 7 deg fov only too and slight yellow tinge (like old civilian CZJ, not totally yellow like east bloc military) but bright and sharp up to 90% of the field. Can be had on euro ebay for 50 bucks or so.

Btw. does anybody know if BH Photo has the Foresta in their NYC Store? If yes, I might take my commie bins for a little comparision when going to NY in september.

Joachim
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