# Are there any binoculars/optical devices which take in a lot of light, but don't magnify? **URL:** \ **Category:** Factual Questions\ **Created:** [November 8, 2013, 9:52pm UTC](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460 "2013-11-08T21:52:30Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [November 9, 2013, 11:06am UTC](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460/41 "2013-11-09T11:06:45Z")
Wikipedia in the article about refracting telescopes says “The combination of an objective lens and some type of eyepiece is used to gather more light than the human eye is able to collect on its own, focus it, and present the viewer with a **brighter** , clearer, and magnified virtual image.” I found a page which uses this terminology: surface brightness (which would be amount of light per unit of solid angle) and “total brightness” (which would be total amount of light received by the eye and what I would call “brightness” whithout qualification). > [@](#): > > [Telescope Equations: Surface Brightness](http://www.rocketmime.com/astronomy/Telescope/SurfaceBrightness.html) > > At the minimum magnification, which is the brightest image you can get, the surface brightness is exactly the same as what you see with your eye. Of course, the image is 30, 40, 50, even 60+ times bigger at that brightness, so **it might be as much as 4000 times the total brightness** , depending on the diameter of the objective. But the surface brightness never exceeds what you can see with your eye alone. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [November 9, 2013, 12:17pm UTC](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460/42 "2013-11-09T12:17:26Z")
> [@sailor](#): > > Wikipedia in the article about refracting telescopes says “The combination of an objective lens and some type of eyepiece is used to gather more light than the human eye is able to collect on its own, focus it, and present the viewer with a **brighter** , clearer, and magnified virtual image.” Since telescopes are often used to view stars, and since stars are point-like, saying the image is brighter doesn’t contradict what people in this thread are saying. > [@](#): > > I found a page which uses this terminology: surface brightness (which would be amount of light per unit of solid angle) and “total brightness” (which would be total amount of light received by the eye and what I would call “brightness” whithout qualification). I, and I suspect most people, would use “brightness” without qualification to mean surface brightness, not total brightness. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [November 9, 2013, 2:47pm UTC](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460/43 "2013-11-09T14:47:51Z")
> [@ZenBeam](#): > > Since telescopes are often used to view stars, and since stars are point-like, saying the image is brighter doesn’t contradict what people in this thread are saying. > > I, and I suspect most people, would use “brightness” without qualification to mean surface brightness, not total brightness. Wikipedia uses “brighter” without qualification to mean total brightness, not surface brightness. Furthermore, if brightness without qualification is understood to mean surface brightness then: - The question “which star is brighter?” is meaningless - The question “which planet is brighter” cannot be answered just by observation and requires calculation regarding total light observed and surface of the disk of the planet. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [November 9, 2013, 2:54pm UTC](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460/44 "2013-11-09T14:54:45Z")
> [@sailor](#): > > I found a page which uses this terminology: surface brightness (which would be amount of light per unit of solid angle) and “total brightness” (which would be total amount of light received by the eye and what I would call “brightness” whithout qualification). > > > [@](#): > > > > [http://www.rocketmime.com/astronomy/...rightness.html](http://www.rocketmime.com/astronomy/...rightness.html) > > > > At the minimum magnification, which is the brightest image you can get, the surface brightness is exactly the same as what you see with your eye. Of course, the image is 30, 40, 50, even 60+ times bigger at that brightness, so it might be as much as 4000 times the total brightness, depending on the diameter of the objective. But the surface brightness never exceeds what you can see with your eye alone. Your quote says precisely what I’ve been trying to explain. My point being, without altering the projected angular size smaller than what the naked eye percieves, you can’t make the image brighter with optics alone. A 1:1 projection will yield you nothing insofar as amplifying brightness, however you define it (indeed, since you’re using imperfect lenses or mirrors, you’d actually be degrading the image if ever so slightly below human perception). Whether you’re projecting this image on a wall or your retina makes no difference. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [November 9, 2013, 3:04pm UTC](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460/45 "2013-11-09T15:04:21Z")
> [@ZenBeam](#): > > I, and I suspect most people, would use “brightness” without qualification to mean surface brightness, not total brightness. Again, we are in the field of semantics in this thread. I would propose that brighter / dimmer refer to total or absolute brightness and darker / lighter would refer to “surface brightness” or “relative brightness” by area unit. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [November 9, 2013, 3:06pm UTC](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460/46 "2013-11-09T15:06:50Z")
> [@cmyk](#): > > Your quote says precisely what I’ve been trying to explain. I do not think your explanations are helping clarify anything. I think from the very beginning we are all here in agreement about the concepts and what is being discussed is the terminology. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [November 9, 2013, 3:09pm UTC](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460/47 "2013-11-09T15:09:53Z")
Alrighty then. Then it’s agreed it’s impossible to construct what the OP describes. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [November 9, 2013, 3:19pm UTC](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460/48 "2013-11-09T15:19:42Z")
> [@sailor](#): > > Again, we are in the field of semantics in this thread. So to be clear, your entire complaint about my first post is semantics? ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [November 9, 2013, 3:57pm UTC](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460/49 "2013-11-09T15:57:30Z")
> [@sailor](#): > > Again, playing with words but the way it is stated I disagree. I have already explained it and I’ll say it again: a telescope or binoculars allow the observer to see objects which he could not see with the naked eye and this is because more light from the same source reaches the eye. This is a fact and I call this “brighter”. I know you’re stuck on semantics right now, but this is already agreed upon in relative terms using _magnification_. The OP asks if it can be done _without_ using magnification. The answer is no. Agreed? ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [November 9, 2013, 3:57pm UTC](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460/50 "2013-11-09T15:57:41Z")
> [@ZenBeam](#): > > So to be clear, your entire complaint about my first post is semantics? The way I interpret it at face value I would say it is wrong. Then you explain that you mean something else which is in agreement with what I think and what the other web sites say. Then I say I agree with the concept as explained but not with the way it was initially expressed. Yeah, I would say that is semantics. Or are we now going to argue about what is and what is not semantics? ---
**Author:** ![bump](https://avatars.discourse-cdn.com/v4/letter/b/7c8e57/32.png) [@bump](https://boards.straightdope.com/u/bump)\ **Post date:** [November 9, 2013, 4:13pm UTC](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460/51 "2013-11-09T16:13:09Z")
Seems like it wouldn’t be too hard to test using photographic lenses on a camera and see what the meter says. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [November 9, 2013, 4:18pm UTC](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460/52 "2013-11-09T16:18:22Z")
> [@cmyk](#): > > I know you’re stuck on semantics right now, but this is already agreed upon in relative terms using _magnification_. > > The OP asks if it can be done _without_ using magnification. The answer is no. > > Agreed? I agree it cannot be done with a simple, two lens, objective-eyepiece, telescope or binocular. I have no idea if it can be done or not with more complex lens combinations. I have seen plenty of camera lenses which were complex enough that I did not understand them. Some had effective focal lengths which were in front or behind the actual lenses which I did not quite understand at the time I saw them. So, while I agree a simple, two piece telescope magnifies brightness in the same proportion that it magnifies area (neglecting losses in the glass), I do not know if this is true for all complex lenses and it has not been shown or proven here. I certainly have never seen such a device that would provide brightness amplification but not size magnification. This does not prove it is conceptually impossible to design and built though. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [November 9, 2013, 4:18pm UTC](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460/53 "2013-11-09T16:18:54Z")
> [@bump](#): > > Seems like it wouldn’t be too hard to test using photographic lenses on a camera and see what the meter says. It wouldn’t at all. Of course, if such a thing were possible, everyone should get back to work on perpetual motion machines. You can change the size of the optics all day, but you can’t change the size of your eye. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [November 9, 2013, 4:22pm UTC](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460/54 "2013-11-09T16:22:20Z")
> [@bump](#): > > Seems like it wouldn’t be too hard to test using photographic lenses on a camera and see what the meter says. There is nothing to test with camera lenses. The light-gathering ability of a camera lens is measured by the f number which is a direct function of the diameter of the lens and its focal length. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [November 9, 2013, 4:32pm UTC](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460/55 "2013-11-09T16:32:44Z")
I’m trying to subvert the semantics and talk straight-up Newtonian physics of incoherent, diffuse light. If it could be done, it would be one hell of a consumer item from the hobbyist to the experimental physics, communications and military fields; et al. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [November 9, 2013, 4:38pm UTC](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460/56 "2013-11-09T16:38:59Z")
I have never seen it done and this I consider a strong indication that it is probably not possible. But it doesn’t prove it. Sailing directly into the wind seemed impossible until it was done. I have not seen proof that a large diameter lens system cannot gather light and concentrate it so it can go into the eye. I understand this cannot be done with a simple two lens telescope because this system just effectively lengthens the eye’s focal length so what you gain one way you lose the other. But I have not seen proof that it is impossible to do with more complex lens systems. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [November 9, 2013, 4:47pm UTC](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460/57 "2013-11-09T16:47:39Z")
“So you’re telling me, that with this lens system, I can use a standard, consumer 100w lightbulb to project film, shot in IMAX, and it’ll project this image at 580x while also amplifying the light as it diffuses across the theater, as if I were using a _[15 Kw lamp?!](http://en.wikipedia.org/wiki/File:Xenon_IMAX_1.jpg)_ I’ll take all you have!” Who has more money than Hollywood? ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [November 9, 2013, 4:49pm UTC](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460/58 "2013-11-09T16:49:54Z")
> [@sailor](#): > > I have never seen it done and this I consider a strong indication that it is probably not possible. But it doesn’t prove it. > > Sailing directly into the wind seemed impossible until it was done. > > I have not seen proof that a large diameter lens system cannot gather light and concentrate it so it can go into the eye. I understand this cannot be done with a simple two lens telescope because this system just effectively lengthens the eye’s focal length so what you gain one way you lose the other. But I have not seen proof that it is impossible to do with more complex lens systems. It goes deeper than optics. The known laws of physics, electromagnetism and thermodynamics themselves, deny it. In short: You’d need to put more _energy_ into the system in order to amplify the wavelengths. 1:1 pure optics = 1:1 energy input/output. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [November 9, 2013, 4:58pm UTC](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460/59 "2013-11-09T16:58:36Z")
I disagree. I do not consider that proof. Just an affirmation. Again, I have seen a few things which seemed impossible because they defied logic and yet they were done. A larger lens that captures more light and funnels it into the smaller eye does not on the face of it violate any laws. It would be interesting to find definite proof though. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [November 9, 2013, 5:05pm UTC](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460/60 "2013-11-09T17:05:05Z")
> [@sailor](#): > > I disagree. I do not consider that proof. Just an affirmation. > > Again, I have seen a few things which seemed impossible because they defied logic and yet they were done. > > A larger lens that captures more light and funnels it into the smaller eye does not on the face of it violate any laws. > > It would be interesting to find definite proof though. The proof is in your own cite, you bolded the the wrong part: > [@rocketmime.com](#): > > [sailor’s cite](http://www.rocketmime.com/astronomy/Telescope/SurfaceBrightness.html) > > "What the heck is that saying? What – that the very brightest image I can get with the scope is exactly the same brightness that I see with the naked eye??? > > Yup. > > Well, remember we’re talking about surface brightness, meaning the brightness per unit area, or the brightness density. At the minimum magnification, which is the brightest image you can get, the surface brightness is exactly the same as what you see with your eye. Of course, the image is 30, 40, 50, even 60+ times bigger at that brightness, so it might be as much as 4000 times the total brightness, depending on the diameter of the objective. **But the surface brightness never exceeds what you can see with your eye alone.** > > This means something else that’s very important – the images in all telescopes operating at minimum magnification have, at best\*, the same surface brightness. Then we can use the brightness at minimum magnification as a reference, and since it is the maximum brightness, we can – and we will – consider it to be 100% brightness." All the equations seemed to be there as well. What more do you need? [Previous page](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460.md?page=2) [Next page](https://boards.straightdope.com/t/are-there-any-binoculars-optical-devices-which-take-in-a-lot-of-light-but-dont-magnify/673460.md?page=4)