You're bordering on the irrational.
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- The nominal luminous power of the binoculars: (1 Viewer)
- Thread starter Rico70
- Start date
You're bordering on the irrational.
Lee.
Pi is an irrational number.
The fixed approximation 0.7854 is bordering on the irrational.
That is what was meant.
The few sandwiches short of a picnic is courtesy of Patrick Moore, as is a few slates short of a roof.
When I was in digs in the North East I could tell what day of the week it was by how many slices of pie there were on the plate.
All the best.
B.
Pi is an irrational number.
The fixed approximation 0.7854 is bordering on the irrational.
That is what was meant.
The few sandwiches short of a picnic is courtesy of Patrick Moore, as is a few slates short of a roof.
When I was in digs in the North East I could tell what day of the week it was by how many slices of pie there were on the plate.
All the best.
B.
Thanks Binny. We have building site across the road and the builder is several trowels short of a tool kit!
All the best
Leo
So an 8x56 is the king of crepuscular binoculars or has the most nominal luminous power?
Hi, Dennis. Twilight binoculars are mainly used by hunters and the best formats are classified by three main characteristics: magnification, exit pupil and tonnage (weight and size).
The 10x70 is also a twilight binocular (one of the best), but it is generally too big and heavy, maybe 2Kg (70oz) against 1Kg of the 8x56. Of course, the power to lighten the twilight (with equal optical quality and construction) is greater in the 10x70 (490pln) than in the 8x56 (390pln), but the latter is much more suitable for transport and quick use freehand (without supports), as needed in hunting.
It can be interesting even without a shotgun, but only to appreciate nature in the most difficult brightness. But as far as I know, generally "birders come home before sunset", because the colors will be less bright without sunlight.
The nominal value consists of the mathematical value resulting from the nominal technical data of the format, without taking into consideration the real differences in magnification, exit pupil and transmittance, etc.
It is said "nominal" to imply that, for example, all binoculars 7x35 are exactly 7x and 35mm in aperture, with the same optical transparency value or other characteristic factor that would differentiate them.
The value of transmittance is also widely discussed in technical environments too. Therefore, the inclusion in this formula can become an important subjective multiplier and deviate on more complex and confusing roads for the average user.
There are those who see 5-6% differences, while I see 2-3% differences. Everyone is also subject very differently from this factor.
This is a graphical representation of the hypothetical exit-pupil/iris needed for twilight observations.
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Nice explanation. Thanks. Interesting ideas. I am sure a 10x70 would be great in low light but like you say a LOT of tonnage. On a tripod it would very cool though. Good for astro use also.
Your right. If the atmosphere is turbulent or you have a lot of light pollution the smaller aperture binocular or scope works better because you are looking through a smaller column of atmosphere. A lot of times I would use my smaller 80mm refractor when observing instead of my 10 inch Dobsonian because the atmosphere was so turbulent. Very few nights were steady enough to use my big 10 inch scope but when it was boy it was it awesome. It was just like you were orbiting the moon with a Nagler eyepiece in that big dobsonian.
For example, the formats 20x100 (500pln) and 25x110 (485pln) according to the formula are also equivalent to 10x70 (490pln) and therefore would have the same capacity in twilight.
But having higher magnification and narrower exit pupil (4.4mm and 5mm vs 7mm), they will be more suitable for night skies with a little light pollution. As Andy says, you only use 10x70 under mag7 skies ... or during twilight, but supported by at least one monopod.
But having higher magnification and narrower exit pupil (4.4mm and 5mm vs 7mm), they will be more suitable for night skies with a little light pollution. As Andy says, you only use 10x70 under mag7 skies ... or during twilight, but supported by at least one monopod.
I want to answer here, to Gijs' statement:
However, if I can make a right objection, then I am sure that in the "complete formula", we are forgetting another much important factor, which is the retinal sensitivity of individuals and their level of perception of light and things.
As also our friend interiception, he mention this here
https://www.birdforum.net/showpost.php?p=3947940&postcount=134
As I have already explained, "my formula" is a deliberately simplified one to include only the nominal values of the binoculars format. Therefore, it makes no sense to include the transmission of light (although it is highly related to the topic - without a doubt).
However, if I can make a right objection, then I am sure that in the "complete formula", we are forgetting another much important factor, which is the retinal sensitivity of individuals and their level of perception of light and things.
As also our friend interiception, he mention this here
https://www.birdforum.net/showpost.php?p=3947940&postcount=134
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Here is your answer, Gijs
But anyone could see it.
Use a camera (even that of the phone) to shoot a burning candle from a dark room from 3m away, then do the same shot from 10cm away. The two shots will have different data about shutter speed or aperture or ISO sensitivity.
And the difference indicates that the more enlarged recovery of the candle flame (the closest one) has a greater amount of light.
Despite this, I do not intend to argue that the intensity of the light has changed, since the candle is always the same, but you do two tests before arbitrarily refuting.
Why do you say this? I have already tried to explain the increase in visibility (not brightness) given by the greater magnification.
But anyone could see it.
Use a camera (even that of the phone) to shoot a burning candle from a dark room from 3m away, then do the same shot from 10cm away. The two shots will have different data about shutter speed or aperture or ISO sensitivity.
And the difference indicates that the more enlarged recovery of the candle flame (the closest one) has a greater amount of light.
Despite this, I do not intend to argue that the intensity of the light has changed, since the candle is always the same, but you do two tests before arbitrarily refuting.
You are simply revisiting the twilight factor.
https://www.swarovskioptik.com/hunting/blog/ontarget_02
Your perception of "bright" changes due to magnification. The light source, as you admit, doesn't change at all. A dim distant light bulb is perceived to be much "brighter" at 100X but it isn't.
If you try to do two calculations you will find that the formula has nothing to do with the "twilight factor". Indeed, this formula is specifically used to indicate the most suitable format at dusk (and not in the moonlight or at night).
I advise you to do two tests seriously, before objecting in vain and without experience. If you have questions about calculations or how to seriously test, you can, I am available.
What specific test(s) would you like to conduct?
WJC
Well-known member
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You have to do the tests at dusk, between about -2° and -9° of height of the Sun (after sunset or before sunrise, of a bright day) or with ambient brightness between about 20 and 2 Cd/m^2.
This can serve
https://www.birdforum.net/attachment.php?attachmentid=713419&d=1577550278
You can also compare non-twilight binoculars with the same "pln" values, or the difference between the formats you have available, taking into account the "pln" values.
A candle or other light source, whether viewed through 8x binos or 100x binos has the same brightness, as both you and Rico have said. But it will be more visible (to use Rico's phrase) through the 100x binos because its image will occupy a much larger proportion of the view and so (to use your words) will be perceived to be much brighter.
As far as I can see then, you and Rico are agreeing.
Lee
