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Nikon 8x20 Lx Vs.10x25?? (1 Viewer)
- Thread starter Donzo98
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Atomic Chicken
Registered with the D.O.E.
Greetings!
I have compared both Nikon HG 8x20 and HG 10x25 models extensively, as well as the Zeiss and Leica (Trinovid and Ultravid) equivalent models. Here's my 0.02:
For compact optics, the 10x25 is superior to 8x20 in almost every way. Brighter, sharper, and better performing in low light conditions, and exhibiting superior sharpness over distance. The only disadvantages to the 10x25's are the usual ones associated with high magnification (restricted FOV, less depth of field, shakiness, etc.).
I'm an unabashed and outspoken fan of low-power optics, 7x being my favorite all around. However, for compact optics, the 8x20 models just don't quite have adequate aperature width to perform as well as the 10x25 models - in my opinion 8x25 would be a MUCH better design for binocular companies to adopt. I think this is a case of ergonomics outweighing optical performance, where the designers decided to reduce the aperature to obtain the same exit pupil size and obtain smaller size/weight as a result - not realizing how much sharpness-over-distance and low light performance would be sacrificed in the process.
I own both Zeiss Victory 8x20's as well as Nikon HG 10x25's, and until the Ultravid compacts appeared I considered both of them to be the best binoculars in their class. Currently, I would rate the Ultravid and Nikon 10x25 models as equals optically, and the Ultravid 8x20 as slightly superior to the Zeiss Victory 8x20. If you choose 10x25 (which I HIGHLY recommend you do!) then it comes down to a question of ergonomics, whether you like the "feel" of the Ultravid or the Nikon better. I personally like the new Ultravid ergonomics very much, but they don't give me the "confidence" regarding their ruggedness that the Nikon does. I will probably end up purchasing a set of 10x25 Ultravids in the future, but for now I'm very happy with my Nikon HG 10x25's and even if I do purchase Ultravids I won't be selling the Nikons - I like them that much.
For me personally, it seems that the ONLY valid reason for choosing an 8x20 over a 10x25 would be the size and weight issues, but there is really so little difference between the two configurations that you should think long and hard before making your decision based solely on this factor.
Best wishes,
Bawko
P.S. Just a side note: the Nikon HG 10x25 is, without question, the best binoculars in terms of edge-to-edge sharpness that I have EVER looked through - regardless of configuration, aperature size, brand, or cost.
I have compared both Nikon HG 8x20 and HG 10x25 models extensively, as well as the Zeiss and Leica (Trinovid and Ultravid) equivalent models. Here's my 0.02:
For compact optics, the 10x25 is superior to 8x20 in almost every way. Brighter, sharper, and better performing in low light conditions, and exhibiting superior sharpness over distance. The only disadvantages to the 10x25's are the usual ones associated with high magnification (restricted FOV, less depth of field, shakiness, etc.).
I'm an unabashed and outspoken fan of low-power optics, 7x being my favorite all around. However, for compact optics, the 8x20 models just don't quite have adequate aperature width to perform as well as the 10x25 models - in my opinion 8x25 would be a MUCH better design for binocular companies to adopt. I think this is a case of ergonomics outweighing optical performance, where the designers decided to reduce the aperature to obtain the same exit pupil size and obtain smaller size/weight as a result - not realizing how much sharpness-over-distance and low light performance would be sacrificed in the process.
I own both Zeiss Victory 8x20's as well as Nikon HG 10x25's, and until the Ultravid compacts appeared I considered both of them to be the best binoculars in their class. Currently, I would rate the Ultravid and Nikon 10x25 models as equals optically, and the Ultravid 8x20 as slightly superior to the Zeiss Victory 8x20. If you choose 10x25 (which I HIGHLY recommend you do!) then it comes down to a question of ergonomics, whether you like the "feel" of the Ultravid or the Nikon better. I personally like the new Ultravid ergonomics very much, but they don't give me the "confidence" regarding their ruggedness that the Nikon does. I will probably end up purchasing a set of 10x25 Ultravids in the future, but for now I'm very happy with my Nikon HG 10x25's and even if I do purchase Ultravids I won't be selling the Nikons - I like them that much.
For me personally, it seems that the ONLY valid reason for choosing an 8x20 over a 10x25 would be the size and weight issues, but there is really so little difference between the two configurations that you should think long and hard before making your decision based solely on this factor.
Best wishes,
Bawko
P.S. Just a side note: the Nikon HG 10x25 is, without question, the best binoculars in terms of edge-to-edge sharpness that I have EVER looked through - regardless of configuration, aperature size, brand, or cost.
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Hi Bawko!
I don't understand in which way the 10x25 is better than the 8x20. I don't believe anyone can se a difference in sharpness between a 20 and 25 mm aperture.
Are they don't of equal quality? If the coating is of the same grade the brightness should be the same, because they have the same exit pupil and brightness index. (In the same way a 7x35 has the same brightness as a 10x50).
Regards, Patric
I don't understand in which way the 10x25 is better than the 8x20. I don't believe anyone can se a difference in sharpness between a 20 and 25 mm aperture.
Are they don't of equal quality? If the coating is of the same grade the brightness should be the same, because they have the same exit pupil and brightness index. (In the same way a 7x35 has the same brightness as a 10x50).
Regards, Patric
Atomic Chicken
Registered with the D.O.E.
Greetings Patric!
First off, the quality of the 8x20 and 10x25 is equal. The coatings, construction, and optics are all top-notch, and the mechanical linkages are tight and smooth.
The main differences are optical - and YES... you can easily tell by looking through both and comparing the images going back and forth between binoculars.
Don't let the specs fool you. Even though the exit pupil is the same, the fact that the 20mm aperature is gathering less light than the 25mm aperature plays an important role in determining overall sharpness, especially as the object being viewed gets farther away from the observer. Also, because of the relative differences in aperature and field of view, the 10x25 ends up delivering a higher intensity of light per square millimeter on the retinal surface than the 8x20, resulting in better brightness and sharpness under low-light conditions. Finally, it is a well known fact that higher power optics will perform better in terms of color detail in low light conditions than lower power optics, and it is for this reason that when I head out the door in the evening I always grab my Pentax SP 10x50's and leave my dearly loved Trinovid 7x42's at home.
I hope this answers your questions...
Best wishes!
Bawko
First off, the quality of the 8x20 and 10x25 is equal. The coatings, construction, and optics are all top-notch, and the mechanical linkages are tight and smooth.
The main differences are optical - and YES... you can easily tell by looking through both and comparing the images going back and forth between binoculars.
Don't let the specs fool you. Even though the exit pupil is the same, the fact that the 20mm aperature is gathering less light than the 25mm aperature plays an important role in determining overall sharpness, especially as the object being viewed gets farther away from the observer. Also, because of the relative differences in aperature and field of view, the 10x25 ends up delivering a higher intensity of light per square millimeter on the retinal surface than the 8x20, resulting in better brightness and sharpness under low-light conditions. Finally, it is a well known fact that higher power optics will perform better in terms of color detail in low light conditions than lower power optics, and it is for this reason that when I head out the door in the evening I always grab my Pentax SP 10x50's and leave my dearly loved Trinovid 7x42's at home.
I hope this answers your questions...
Best wishes!
Bawko
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Robert Ellis
Larus marinus
From what I have found, and at birding distances, there is a threshold for the ability to ggrab detail somewhere between 25 and 20mm. With my 7x21 I notice lack of detail at distances, with my 7x26 it is there, and these bins are otherwise optically equivalent. The difference between the 26mm and a 30mm is far less noticeable, making me believe that the eye need a minimum amount of objective to gather enough detail for the brain. Objectives wround 25mm or greater with high quality behind them seem adequate for most birding, whereas 20mm is a tad small for extreme distences.
I would not hesitate to use the 8x20s for all birding if forced to.
I would not hesitate to use the 8x20s for all birding if forced to.
Hi Bawko, and thanks for your reply!
I have thought much about these things, and there are some factors that affect the result of the viewing.
At first I know that a large aperture will give more details than a small, even with the same magnification. The difference IN PRACTICE can not be directly proportional to the diameter, however. In that case a 20x50 would give four times more details than a 10x25, and a 10x50 would give the same resolution as a 20x25. But of course, the 20x power is superior to 10x, more than 50mm aperture is superior to 25mm, (providing you looking at daytime). For me it's also obvious that a 10x50 isn't double the details the eye can see in comparison to a 10x25. The resolution is twice in theory, but the gain of it is limited by our eye.
About the exit pupil and brightness my line of reasoning is this: a 25mm lens gathers 56% more light than a 20mm lens. Using the same magnification that result in an improvement of the brightness with 56%. A 8x25 is 56% brighter than a 8x20. When using 10x power with 25 mm lens, the same light amount is spread out on 56% bigger area than 8x, and the result has to be that the light amount/area is the same as with a 8x20. This is just physical laws...
Or is it really some important factor I have missed in my reasoning?
Another simile I can give is following: If you look with the naked eye through a hole of 2,5mm diameter, you will se the brightness of any binocular or telescope with this exit pupil. Actually even brighter, because there is no light loss of glass surfaces. If you through this hole study a candle at 10m distance and then approach to 5 m, is the candle shining stronger? No, it doesn't, the luminosity of a light source is the same undependent of the distance. But the LIGHT AMOUNT reaching your eye is four times bigger, because the visible area of a light source became four times bigger when half the distance. This situation is completely comparable to change from a 10x25 bino to a 20x50. The exit pupil is the same and the brightness is the same, but the light amount from the candle is four times bigger.
My reasoning is also refered to my own experiences. I have both a 5x25 and a 10x50 binoculars. Is the 10x50 brighter? No, it isn't, the 5x25 is comparable in brightness, it is in par to the 10x50 for night use. In the 10x50 you will be much more dazzled when looking at street lanterns, car beams and the moon, because of the four time bigger light amount with twice the power, but that isn't mean the image is brighter. I have also compared a Nikon 7x20 to a Nikon 10x25, and noticed that the 7x20 gave a considerable brighter image. Actually what I could estimate as the difference between the brightness index of them: 8,16/6,25=1,3 (30% brighter).
I believe that the thought of a 10x25 brighter than a 8x20, or a 10x50 brighter than a 7x35 is based on a misunderstanding, that people have confused the brightness to the light amount. (when looking at light sources they became more dazzled).
If you experience the 10x25 brighter than the 8x20, I think it may have a better percentual effectivity (I don't find the english word for it just now), because of slightly better coating.
Or make this comparison: drill a hole of 2,5 mm in a plate and look through it and compared to your 10x25, or a 5mm hole and compare to a binocular with 5mm exit pupil. If a 10x25 is noticable brighter than a 8x20, the both of them will be considerable brighter than looking through this 2,5 mm hole. I dare to claim that they are not brighter at all.
With the kindest regards, Patric
I have thought much about these things, and there are some factors that affect the result of the viewing.
At first I know that a large aperture will give more details than a small, even with the same magnification. The difference IN PRACTICE can not be directly proportional to the diameter, however. In that case a 20x50 would give four times more details than a 10x25, and a 10x50 would give the same resolution as a 20x25. But of course, the 20x power is superior to 10x, more than 50mm aperture is superior to 25mm, (providing you looking at daytime). For me it's also obvious that a 10x50 isn't double the details the eye can see in comparison to a 10x25. The resolution is twice in theory, but the gain of it is limited by our eye.
About the exit pupil and brightness my line of reasoning is this: a 25mm lens gathers 56% more light than a 20mm lens. Using the same magnification that result in an improvement of the brightness with 56%. A 8x25 is 56% brighter than a 8x20. When using 10x power with 25 mm lens, the same light amount is spread out on 56% bigger area than 8x, and the result has to be that the light amount/area is the same as with a 8x20. This is just physical laws...
Or is it really some important factor I have missed in my reasoning?
Another simile I can give is following: If you look with the naked eye through a hole of 2,5mm diameter, you will se the brightness of any binocular or telescope with this exit pupil. Actually even brighter, because there is no light loss of glass surfaces. If you through this hole study a candle at 10m distance and then approach to 5 m, is the candle shining stronger? No, it doesn't, the luminosity of a light source is the same undependent of the distance. But the LIGHT AMOUNT reaching your eye is four times bigger, because the visible area of a light source became four times bigger when half the distance. This situation is completely comparable to change from a 10x25 bino to a 20x50. The exit pupil is the same and the brightness is the same, but the light amount from the candle is four times bigger.
My reasoning is also refered to my own experiences. I have both a 5x25 and a 10x50 binoculars. Is the 10x50 brighter? No, it isn't, the 5x25 is comparable in brightness, it is in par to the 10x50 for night use. In the 10x50 you will be much more dazzled when looking at street lanterns, car beams and the moon, because of the four time bigger light amount with twice the power, but that isn't mean the image is brighter. I have also compared a Nikon 7x20 to a Nikon 10x25, and noticed that the 7x20 gave a considerable brighter image. Actually what I could estimate as the difference between the brightness index of them: 8,16/6,25=1,3 (30% brighter).
I believe that the thought of a 10x25 brighter than a 8x20, or a 10x50 brighter than a 7x35 is based on a misunderstanding, that people have confused the brightness to the light amount. (when looking at light sources they became more dazzled).
If you experience the 10x25 brighter than the 8x20, I think it may have a better percentual effectivity (I don't find the english word for it just now), because of slightly better coating.
Or make this comparison: drill a hole of 2,5 mm in a plate and look through it and compared to your 10x25, or a 5mm hole and compare to a binocular with 5mm exit pupil. If a 10x25 is noticable brighter than a 8x20, the both of them will be considerable brighter than looking through this 2,5 mm hole. I dare to claim that they are not brighter at all.
With the kindest regards, Patric
Atomic Chicken
Registered with the D.O.E.
Patric,
You are correct in terms of the pure physics of light, but when the light interacts with the lenses of the optics, then the human retina, the situation becomes more complex.
The field of view determines the "width" of the resulting image on the retina. Because the 10x25 has a smaller field of view, the same amount of light is "spread" across a smaller area of the retina than an 8x20 image would be. Because the resulting intensity per square millimeter of light energy is greater, as the light fades the human eye will see a brighter image.
This is not as simple as the phenomenon of light as it appears at the eyepiece of the binocular, but rather a 2-part system: The binocular optics AND the optics of the human eye.
Hope this adds something to the discussion... but in the end nothing really compares to actual real-world observations. My own observations have conclusively demonstrated (at least to myself) that the 10x25 is the superior configuration for compact binoculars... at least in terms of detail over distance and low-light performance. This is not what I would prefer, again I am a low-power fan and generally prefer the image characteristics of 7x and 8x optics over 10x. However, the physical laws of the universe don't really care about what I would prefer, they are what they are.
Best wishes,
Bawko
You are correct in terms of the pure physics of light, but when the light interacts with the lenses of the optics, then the human retina, the situation becomes more complex.
The field of view determines the "width" of the resulting image on the retina. Because the 10x25 has a smaller field of view, the same amount of light is "spread" across a smaller area of the retina than an 8x20 image would be. Because the resulting intensity per square millimeter of light energy is greater, as the light fades the human eye will see a brighter image.
This is not as simple as the phenomenon of light as it appears at the eyepiece of the binocular, but rather a 2-part system: The binocular optics AND the optics of the human eye.
Hope this adds something to the discussion... but in the end nothing really compares to actual real-world observations. My own observations have conclusively demonstrated (at least to myself) that the 10x25 is the superior configuration for compact binoculars... at least in terms of detail over distance and low-light performance. This is not what I would prefer, again I am a low-power fan and generally prefer the image characteristics of 7x and 8x optics over 10x. However, the physical laws of the universe don't really care about what I would prefer, they are what they are.
Best wishes,
Bawko
Atomic Chicken said:
Bawko,
That is an interesting matter, actually I have self wondered about the FOV affects the visible brightness when I look at the stars. If I have same power, same aperture but wider field, then I see more stars, and consequently get more total light amount to my eye. But the light amount depends on the size of the aperture. Would that mean the brightness in practice decrease with a wider field despite same exit pupil, otherwise would the total possible light amount not be constant...? If that is right, it would be the reason the mostly 7x50 binos are made with a small AFOV, to really get the highest possible brightness. But I doubt a bit, it would easy be proven comparing 10x50, 5 degrees binos with 10x50, 7 degrees. The 10x50 with 5 degrees FOV would in that case have twice the brightness...or that should mean that 8x30 binos with 50 degrees AFOV has the same brightness as 8x42 binos with 70 degrees.
Another discussion is about if you see a brighter image with a binoculars than with a monocular. At Cloudy nights astronomical forum there I'm also a member this matter has been discussed. Some people claims that you get a brighter image using both eyes than one. Other deny it. I don't know, I have squinting eyes and can't experience stereoscopic viewing...
About the relation between brightness and color detail in low light conditions I reasoning following: If you compare a 7x35 to a 10x40, the 7x35 gives a much brighter image at dawn and dusk. Despite the darker image with 10x40 in low light you will benefit from the 10x40 when it comes to details, providing it isn't TOO dark outside. But will you se better colours? I am doubting. What is the main condition for getting colours to appear? I think it's brightness.
I have heard before about those theorys of "more energy to the eye" with a bigger aperture and more power. But if that would be the case the naked eye would give us very bad colour reproduction! I don't think any binoculars are better in this respect.
I think many things in this area are hard to proof on a scientific basis, because we have to do with combination of technical instruments and the human biology. It's a common idea that higher power increase color reproduction more than lower power and better brightness, but it's still a theory, which I'm sure isn't proofed on a scientific basis.
Someone has produced a matematical formula for the percentual gain in brightness using both eyes than one, but that is still a theory which lacks scientific proof. Different people have different opinions, depending on their own experiences.
But it's interesting subjects, I hope I'm not too hard or obstinate here... I just don't easy accept theorys on the basis of peoples experiences before I self have tried them and got the same conclusion. Especially when they seem to be in oposition to the physical/optical laws.
With kindest regards, Patric
henry link
Well-known member
Patric,
My experience mostly agrees with yours. If the light transmission of the binoculars being compared is equal then the surface brightness of an evenly illuminated real field (for instance a cloudless blue sky) will appear equally bright in all binoculars of the same exit pupil, whether they are 8X20's or 40X100's. The number of photons which fall on a given area of retina will be equal. Also, FOV only effects the size of the retinal projection. It has no effect at all on the intensity of light that falls on the illuminated area of the retina.
Henry
BTW I visited Lulea in June of 1967. I spent the summer traveling in Europe and decided to take the train as close to the Arctic circle as my Eurailpass would allow. I mainly remember the long spectacular train ride through boreal forests with sunsets and sunrises that must have lasted for hours.
My experience mostly agrees with yours. If the light transmission of the binoculars being compared is equal then the surface brightness of an evenly illuminated real field (for instance a cloudless blue sky) will appear equally bright in all binoculars of the same exit pupil, whether they are 8X20's or 40X100's. The number of photons which fall on a given area of retina will be equal. Also, FOV only effects the size of the retinal projection. It has no effect at all on the intensity of light that falls on the illuminated area of the retina.
Henry
BTW I visited Lulea in June of 1967. I spent the summer traveling in Europe and decided to take the train as close to the Arctic circle as my Eurailpass would allow. I mainly remember the long spectacular train ride through boreal forests with sunsets and sunrises that must have lasted for hours.
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elkcub
Silicon Valley, California
Donzo98 said:
Don,
I can't speak to the Nikon line, but can confirm Bowko's observations about the functional superiority of Swarovski's 10x25 SLC over the 8x20 SLC. This is only my opinion, but it is based on several yrs. of living with both instruments.
Whatever you do enjoy the view.
Elkcub
Atomic Chicken said:
Hi Bawko,
I agree with your assessment of the specific types of binos you mentioned. But back to Don´s question I have to say: strange, in my case it´s vice versa. I prefer high powered binoculars like 10-15x but when it comes to pocket binos I like the little ones more. The main reason is shaking. Because of their light weight pocket binos tend to shake even in my hands and I use to hold a 15x bino without stabilisation or tripod support quite often. A higher magnification makes this not welcome effect more visible. Pocket binos also suffer from small FOVs. With a higher magnification of 10x the view is even narrower. And third most 8x20s have a closer focus than their 10x25 equivalent. I forgot one more thing to mention. An 8x20 has also a better depth of field. The older you get the more this would be visible because the abilty to adapt decreases with age. I like to take pocket binos for long walks watching also at insects and other small animals or plants on the ground. A lot of 10x25 (e.g. the 10x25 Nikon LX/HG IMHO) aren´t even real pocket binos since they simply don´t fit in a normal pocket because of their weight and size. What I like with the 10x25s is that my hands have more material to touch so that it´s more comfortable to hold them.
Steve
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elkcub
Silicon Valley, California
hinnark said:
Steve,
I must be a third variant. I can hold either my heavy 10x42 SLCs or light 10x25 SLCs steadier than 8x30 or 8x20s. For Swaros, incidentally, the AFOV is slightly larger for the 10x (54 deg.) than the 8x (52.8 deg). I agree with you about the short focus advantage of the 8x, but that is offset for me by much better long distance viewing — most recently Hawaiian surfboarding at ~ 500-1000 m.
-elk
Light amount vs brightness
That is a very good example you give, Henry!
People may in some situations experience a brighter image using higher magnification despite same exit pupil, when the brighter areas in the field will growe in size and dazzle more, which they easy confuse to brightness.
But looking at an even area or surface, like an even blue heaven or an even coloured house wall will give the same brightness, providing the optical instruments has equal light transmission.
That is also likely the reason to the common belief that a binocular can give a brighter image than the naked eye. But the brightness of an optical instrument is always less than the naked eye and can never exceed the eye pupil brightness index X light transmission value. Accordingly a binocular can at it's best perform about 95-96% of the brightness of the naked eye.
One example I have of this misunderstanding is a former neighbour to me who was impressed by the brightness of a Leica binocular, he said: "when I looked through the Leica, it was like turn on ten lamps". Sure he experienced it was a very bright image in the Leica, compared to a budget bino with bad light transmission. He was likely also looking at some lamp through the Leica, and became very dazzled by the multiple times light amount which was reaching his eyes compared to naked eye view. It was the light amount which exceeded the naked eye view, not the geometrical brightness.
Regards, Patric
When you were here I had a month left to be born, but my parents didn't live in Luleå at that time. I'm born in Boden (40km north of Luleå), raised up the early years in Svappavaara (about 50km south of Kiruna). I live in Luleå since 1976. I'm sure you enjoyed the exotic sunny nights here, if they didn't destroyed your sleeping...
henry link said:
That is a very good example you give, Henry!
People may in some situations experience a brighter image using higher magnification despite same exit pupil, when the brighter areas in the field will growe in size and dazzle more, which they easy confuse to brightness.
But looking at an even area or surface, like an even blue heaven or an even coloured house wall will give the same brightness, providing the optical instruments has equal light transmission.
That is also likely the reason to the common belief that a binocular can give a brighter image than the naked eye. But the brightness of an optical instrument is always less than the naked eye and can never exceed the eye pupil brightness index X light transmission value. Accordingly a binocular can at it's best perform about 95-96% of the brightness of the naked eye.
One example I have of this misunderstanding is a former neighbour to me who was impressed by the brightness of a Leica binocular, he said: "when I looked through the Leica, it was like turn on ten lamps". Sure he experienced it was a very bright image in the Leica, compared to a budget bino with bad light transmission. He was likely also looking at some lamp through the Leica, and became very dazzled by the multiple times light amount which was reaching his eyes compared to naked eye view. It was the light amount which exceeded the naked eye view, not the geometrical brightness.
Regards, Patric
When you were here I had a month left to be born, but my parents didn't live in Luleå at that time. I'm born in Boden (40km north of Luleå), raised up the early years in Svappavaara (about 50km south of Kiruna). I live in Luleå since 1976. I'm sure you enjoyed the exotic sunny nights here, if they didn't destroyed your sleeping...
Robert Ellis
Larus marinus
Again, don't think in terms of brightness, but the ability to funnel detail into your eye. A 25mm objective will gather more light, not for the sake of brightness, but to provide the eye more detail.
Light reflected froom the object you are looking at expands in a sphere in all directions and for binoculars there are two implications of this.
1- As the observer is further and further away the light is further anf further spread out.
2- A larger objective will intercept more of this light at the same distance, or the same amount at a proportionally greater difference.
The human eye has a threshold of light it needs for detail. From experience at birding distances, save extreme distance i.e. over water, 20mm is a tad lacking whereas 25 is getting very close to what the eye craves.
25mm compacts, regardless of magnification, make for better birding glasses than 20mms because of the greater ability to gather and refocus the expanding light form the object. Considering these lines are made in 8x20 and 10x25 only, the 25s would be better at getting detail to the eye, exit pupil be damned.
You people really should listen to me more, geepers. Detail, not brightness, makes for a better image.
Light reflected froom the object you are looking at expands in a sphere in all directions and for binoculars there are two implications of this.
1- As the observer is further and further away the light is further anf further spread out.
2- A larger objective will intercept more of this light at the same distance, or the same amount at a proportionally greater difference.
The human eye has a threshold of light it needs for detail. From experience at birding distances, save extreme distance i.e. over water, 20mm is a tad lacking whereas 25 is getting very close to what the eye craves.
25mm compacts, regardless of magnification, make for better birding glasses than 20mms because of the greater ability to gather and refocus the expanding light form the object. Considering these lines are made in 8x20 and 10x25 only, the 25s would be better at getting detail to the eye, exit pupil be damned.
You people really should listen to me more, geepers. Detail, not brightness, makes for a better image.
henry link
Well-known member
Binoculars are a special case when it comes to detail. Because the magnifications are so low objective apertures are not the limiting factor as they are in higher powered telescopes. Every good binocular presents the eye with more detail than can actually be seen, even 8X20's. If we assume equal quality diffraction limited optics (binoculars are never quite that good) the smallest details in the image produced by an 8X20 would be 46.4" (5.8"X 8= 46.4"). The smallest details in a 10X25 would also be 46.4" (4.64" X10=46.4). The eye's resolution is about 60" so the smallest details in both binoculars are not visible to the eye by an equal amount, so both images should look equally sharp. Of course more actual detail is visible in the 10X25 than the 8X20, not because the objective is wider but because the smallest details are 25% larger. The general rule of thumb in optics is that the resolution of a telescope image matches daylight eyesight resolution at a 2mm exit pupil. The image from any larger exit pupil will contain more detail than the eye can see. In the case of high quality telescopes I've found that even a 1mm exit pupil image contains a little more detail than I can see in daylight.
elkcub
Silicon Valley, California
henry link said:
Hello Henry,
I certainly accept all that you've said technically.* However, I might point out that there is a strong tendency to consider the light gathering and/or resolution capabilities of the optics to the exclusion of the human visual system, which, in the end, must garner information from the magnified image projected onto the retina. So, when you say:
this is easily (and often) interpreted to mean that small target images are just as effective as larger ones. After all, they both contain the same overabundance of information. Right? Similarly, the previous posts about equivalent uniform field brightness in binoculars with the same exit pupil doesn't take into account that brightness is typically judged from the non-uniform images the user selects for projection onto the retina.
Returning to the main issue of this thread, then, I would suggest that Bawko's basic observation about the relative merit of the 10x25 configuration is plausible from the user's perspective — particularly at low light levels. Namely, the more limited field of the 10x25 allows higher contrast target areas to be selectively projected onto the retina, and the greater magnification further helps to ferret out details otherwise lost at lower power. It might also be mentioned that acuity falls off drastically in low-light, and in going from 8x to 10x one effectively increases the retinal sensors associated with interpreting the target area by (100 - 64)/64 = 56%.
Anyway, these comments are not at all intended to contradict what you've said, but simply to round out the discussion with more aspects of the visual/perceptual system.
Elkcub
* On re-reading, I must be missing something fundamental to the equal resolution argument about 10x25 and 8x20. Also, I don't understand the telescope image resolution matching procedure.
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Robert, Henry and Elkcub,
Because of my lacking understanding in all specific terms and expressions in english language, I don't completely understand all your reasoning in your last contributions.
But my conclusion are following, are we agree in this?:
*Every optical system with the same exit pupil and equal light transmission has the same geometrical brightness, undependent if it is a pocket binocular or a huge astronomical telescope.
*The theoretic resolution of a binocular is better with a big aperture than a small one, even with the same magnification. The practical gain of the increased resolution using a bigger aperture is finite by our eyes, however.
According to my own experiences I don't believe we benefit very much from a large aperture than a small, if the magnification at the same time isn't higher.
I have owned many binoculars during the years. The sharpest optics I have ever had was a Zeiss 6x20 monocular. The sharpness of it was superior to every other optical instrument I have had, including Carl Zeiss Jena 7x50, Celestron Ultima 8x56, Pentax 16x60 PCF WP, and Oberwerk 11x70 binoculars. None of them in par to the Zeiss 6x20 in optical quality, but therefore not of bad quality.
That makes me convinced that we benefit much more from a sharper optical quality than larger aperture. Some claims that they really se more details using 25mm aperture than 20mm. I personally doubt that you will benefit much from using a 8x25 than a 8x20 when it comes to resolution. Do you really see more details at daytime with a 10x50 than a 10x40? Isn't the main reason you see more details through a 10x25 than a 8x20 that the image scale is 25% larger?
Regards, Patric
Because of my lacking understanding in all specific terms and expressions in english language, I don't completely understand all your reasoning in your last contributions.
But my conclusion are following, are we agree in this?:
*Every optical system with the same exit pupil and equal light transmission has the same geometrical brightness, undependent if it is a pocket binocular or a huge astronomical telescope.
*The theoretic resolution of a binocular is better with a big aperture than a small one, even with the same magnification. The practical gain of the increased resolution using a bigger aperture is finite by our eyes, however.
According to my own experiences I don't believe we benefit very much from a large aperture than a small, if the magnification at the same time isn't higher.
I have owned many binoculars during the years. The sharpest optics I have ever had was a Zeiss 6x20 monocular. The sharpness of it was superior to every other optical instrument I have had, including Carl Zeiss Jena 7x50, Celestron Ultima 8x56, Pentax 16x60 PCF WP, and Oberwerk 11x70 binoculars. None of them in par to the Zeiss 6x20 in optical quality, but therefore not of bad quality.
That makes me convinced that we benefit much more from a sharper optical quality than larger aperture. Some claims that they really se more details using 25mm aperture than 20mm. I personally doubt that you will benefit much from using a 8x25 than a 8x20 when it comes to resolution. Do you really see more details at daytime with a 10x50 than a 10x40? Isn't the main reason you see more details through a 10x25 than a 8x20 that the image scale is 25% larger?
Regards, Patric
elkcub
Silicon Valley, California
Swedpat said:
Patric,
Yes, the reason we see (i.e., apprehend, perceive) more detail, is because the image is larger and the nervous system can therefore process the information better. All of this relates to "visual acuity," which is compromised with decreasing illumination but aided by increasing retinal image size. While reading, for example, one moves closer to the printed page under dim lighting conditions. Optical magnification effectively moves us closer to the object of interest, and spreads the projected image over a larger portion of the retinal matrix. Arguably larger object images are always easier to process by the nervous system. To obtain a larger image, however, one must trade off other important factors such as FOV, DOF, weight, etc.
Elkcub
henry link
Well-known member
Atomic Chicken said:
Hello elk and Bawko,
Happily, I think we are in complete agreement about magnification in binoculars. More magnification allows the eye to see more detail under any lighting conditions. However, the above quote about FOV is simply not correct and I think it can only cause confusion. I haven't checked, but for the moment lets assume that the Nikon 8X20 and 10X25 have the same AFOV. This could be true even if it isn't since many sibling bins like this use the same eyepiece. If the AFOV's are identical that means the area of retinal projection is identical for both. AFOV determines the size of the retinal projection, not real FOV. But really that hardly matters as far as brightness is concerned, because the size of the retinal projection has no effect on the brightness of the light within it. In this particular case the larger size of an object in the image of the 10X25 precisely matches the increase in objective size so the surface brightness of the object and the "intensity per square millimeter of light energy" on the retina is identical in the 10X25 and the 8X20, no matter what the lighting conditions. Its very likely that you will see the object more clearly through the 10X25 in low light, but only because it's larger, not because it's brighter.
I'm sure elkcub remembers that he, Ikka and I endured a long thread on the subject of FOV and brightness last year. I don't think I've got the stamina for doing that again.
Best Regards,
Henry
Atomic Chicken
Registered with the D.O.E.
henry link said:
Henry,
Checking the specifications, I find that the 8x20 and 10x25 by Nikon are indeed very close to each other in terms of AFOV (54.39 Deg. vs. 53.86 Deg. respectively). This would, on the surface, seemingly support your contention that the two should be equally bright.
However, when you consider the raw light gathering power of the surface of the objective lens, expressed in square millimeters of area, a different story emerges. The 8x20 gathers whatever light is available through an objective lens area of 314.16 square millimeters, while the 10x25 gathers light through an objective lens area of 490.87 square millimeters - a difference in area of roughly 36%. Keeping in mind that after going through the binocular optics and being magnified down to the same exit pupil size (2.5mm), then projected onto the retina as roughly the same size AFOV projection, it turns out that under low light conditions the 10x25 should be providing over 1/3 more light to the retinal surface than the 8x20.
I agree that my initial post was in error regarding the FOV difference between the 2 models causing greater light intensity, and I thank you for pointing that out. However, my assertion still stands that the 10x25 performs better under low light conditions because of raw physical factors (higher light intensity projected onto the retina) - along with the variously discussed psychooptical factors at work due to the larger magnified image elements.
I look forward to further discussion - this has turned into a very interesting thread!
Best wishes,
Bawko
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