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why do the 8x50 and 10x50 Ultravid have the same FOV? (1 Viewer)
- Thread starter 308CAL
- Start date
Quote: 'it seems that the 8x should have a larger FOV, why buy the 8 over the 10 if the FOV is the same?'
I would guess that the 10X50 has a wider apparent field of view than the 8X50.
Yes, I've just looked at the Tech spec on Leica website. 6.7 degree true field for both binoculars, so the the apparent field for the 8X binocular is 53.6 degrees and 67 degrees for the 10X binoculars.
Choose the 8X50 if you want a large exit pupil (perhaps for astronomical use). The 10X50 will be fine for low light/dusk, plus extra power.
andytyle
I would guess that the 10X50 has a wider apparent field of view than the 8X50.
Yes, I've just looked at the Tech spec on Leica website. 6.7 degree true field for both binoculars, so the the apparent field for the 8X binocular is 53.6 degrees and 67 degrees for the 10X binoculars.
Choose the 8X50 if you want a large exit pupil (perhaps for astronomical use). The 10X50 will be fine for low light/dusk, plus extra power.
andytyle
black lark
Registered User
Hi. This is my first post here and I am dragging up an old thread because I am interested in the Ultravid 10x50.
I'm relatively new to binoculars as a hobby (long background in photography and passion for optics), having used an Ultravid 10x32 for the past few years, mostly for general spotting when going hiking/camping/cycling and sometimes around the city. I am also a 'lunatic' - obsessed by the moon and interested in doing some star gazing when I am in the countryside.
I thought I had well understood the concepts of field of view (true and apparent). I understand that similar e.g. 8x42 binoculars can have different fields of view as a function of objective and eyepiece design. I also understand that x50 binos usually have a smaller FoV than x42 binos (for the same reason).
What I am unable to visualise (so I guess I have not understood so well) is how the Ultravid 8x50 and 10x50 can have identical fields of view at different magnifications (117m at 1000m, or 6.7 degrees). I am unable to visualise how the view would differ between these two binos (other than that the 8x view appears smaller in the binos)? Can someone help me understand this?
I'm relatively new to binoculars as a hobby (long background in photography and passion for optics), having used an Ultravid 10x32 for the past few years, mostly for general spotting when going hiking/camping/cycling and sometimes around the city. I am also a 'lunatic' - obsessed by the moon and interested in doing some star gazing when I am in the countryside.
I thought I had well understood the concepts of field of view (true and apparent). I understand that similar e.g. 8x42 binoculars can have different fields of view as a function of objective and eyepiece design. I also understand that x50 binos usually have a smaller FoV than x42 binos (for the same reason).
What I am unable to visualise (so I guess I have not understood so well) is how the Ultravid 8x50 and 10x50 can have identical fields of view at different magnifications (117m at 1000m, or 6.7 degrees). I am unable to visualise how the view would differ between these two binos (other than that the 8x view appears smaller in the binos)? Can someone help me understand this?
John M Robinson
Well-known member
I can’t help you. Like you, I’m more familiar with photography, where FOV naturally shrinks as magnification goes up, all else being equal.
casscade
Well-known member
Personally I’d go for the 10x, the 8x50 leica has an awful apparent fov and feels as such. I’ve had many of both and the closed in restrictive tunnel vision fov is why I personally never liked the 8x50 Leica. The 10x50 has a great immersive fov, even by todays standards, especially considering how old its design is.
hoolyp,
I agree with casscade the UVHD+ 10x50 has a "great immersive view" including both very good true and apparent field of view. The 10x50 should be much more suitable than the 8 for casual astronomy especially with respect to the moon. I have never seen an 8x50 UV and can't say why the true field of view would be the same in both.
Mike
I remember this used to puzzle me as well, I assumed that an 8x (any 8x for that matter) would produce a magnification and render an image comparable to any other 8x (in terms of what you see), and so on with 10x, etc. The explanation is very simple (excuse the lack of technical terms, no aspiration whatsoever, just a desire to help).
You probably know how in the movies the "1st person view" of someone looking through binoculars is two circles joined together, while anyone who has ever actually used binoculars has experienced that what your eyes actually see is a circle, you probably know what I mean. So, let's take that "circle", that's the image you see. Any 8x will show things magnified similarly (although things like apparent field of view or the fact that the binoculars are Porro or roof can alter your personal perception of magnification, but that's another story). So, a 6,7º 8x and a 8,8º 8x will show things magnified 8 times, but the second has a much larger field of view (FOV) which, being both binoculars 8x (same magnification) will produce a larger apparent field of view (AFOV). I've made a simple sketch to help you visualize it.
When you look at something, like the loquat tree in my garden, what you see is trapped inside that "circle of image" we've mentioned. Well, to help you grasp this concept, I actually want you to focus on what is "outside" of that circle where the image is. You've probably experienced, that the image has a round limit (called "field stop"), and everything beyond that point is black. Well, using the example of the 8x50 and 10x50 Ultravids, both having 6,7º FOV, the "amount of black" around the image will appear bigger on the 8x (or, to put it in other words, the circle of image will appear smaller), while on the 10x there will be "less black" around the circle of image, the circle of image will appear larger, it will fill your eyes.
The field of view our eyes see is somehow an ellipse, but the image you see through the binoculars is like a circle inside your field of view. Have a look at this: same image, same "actual" field of view, different "apparent" field of view.
This is the reason many people prefer binoculars with larger AFOV, and 10x are typically good at this, and many people prefer it. Not only do they get more resolving power (although many times this is negated by the increased shake), but they also get "a bigger picture", and that can bee addictive, everything it's more "in your face". If you read binocular reviews, you'll probably come across people referring to binoculars with big AFOV as having a "window view", implying that you get an immersive image, like you were not using binoculars. On the other hand, you will read people referring to looking through binoculars with a small AFOV as peering through a keyhole or a straw.
AFOV can be calculated in degrees, there is a quick (but not exact way) simply by multiplying magnification by actual FOV in degrees, like @andytyle says, 53.6º for the 8x and 67º for the 10x. However, then there is a more complex formula to get the actual figure. Depending on the country (if I remember correctly, I'm happy to stand corrected), beyond 60º (or was it 65º?) of AFOV is considered "wide angle". Some people find a figure in this region of 60º to be pleasing, and going below 55 or 50º to be too compromised, but YMMV.
I hope this helps
Many thanks to all of you for your replies, and particularly the one above. Your explanation is what I had intuited (and what I meant when I asked if the 8x image is 'smaller'). Whilst I'm interested in the technical reasons I was much more interested in understanding the 'bottom line' in terms of image experienced by the eyes/brain between these two bins.When you look at something, like the loquat tree in my garden, what you see is trapped inside that "circle of image" we've mentioned. Well, to help you grasp this concept, I actually want you to focus on what is "outside" of that circle where the image is. You've probably experienced, that the image has a round limit (called "field stop"), and everything beyond that point is black. Well, using the example of the 8x50 and 10x50 Ultravids, both having 6,7º FOV, the "amount of black" around the image will appear bigger on the 8x (or, to put it in other words, the circle of image will appear smaller), while on the 10x there will be "less black" around the circle of image, the circle of image will appear larger, it will fill your eyes.
I hope this helps
I did not mention in my post but I also acquired an 8x42 UV recently - I wanted to try the easier/brighter viewing and still trial an 8x magnification in addition to my 10x32. So far I absolutely love them and for most purposes am happy to with the slight extra bulk compared to the 10x32 (except e.g. bike camping, where every gram and square inch count). The jury is still out on 8x or 10x but I'm enjoying the journey.
8x50 was not really in my focus, but I'm pretty interested in the 10x50 and wanted to understand the difference between the x50 UVs better. It's clear to me that my existing pairs already give me a versatile kit but I'd like to experience a larger binocular, in particular for night skies (and they hold their value fairly well).
has530
Well-known member
There are a few physical factors that lead to the counter-intuitive fact you have discovered that larger (e.g. 50mm) lower powered (8x vs. 10x) binoculars tend to have narrower FOVs.
First one must understand that the magnification is the ratio of the objective lens and eyepiece focal lengths. As you increase the objective lens size, so do the focal lengths (binoculars typically operate with f/3 to f/5 objectives, anything faster results in a poorly corrected image and larger can get quite long! For example an f/10 objective in a 50mm binocular would result in a pair about 2 feet in length). Thus, in order to achieve a focal ratio of 8x, a 50mm binocular may need an eyepiece with twice the focal length. Well corrected, wide angle, long focal length eyepieces can quite large and unwieldy (for example the pentax xw 40mm, a very nice long focal length eyepiece weighs in over 27 ozs, more than many pair of binos on their own!).
Along the same lines, the total field of view is set by the field stop (and focal length of the eyepiece). The field stop is an aperture in the eyepiece/focal plane of the objective. For a long focal length eyepiece to achieve a wide field of view it must have a wide field stop diameter. Such a large image at the field stop also requires large prisms to carry the light cone to avoid vignetting. In many cases such large prisms and eyepieces are impractical for handheld optical devices.
Another factor may be cost. Large well corrected glass components are expensive, especially for non-spherical lens types often used in wide angle eyepieces. Additionally for ease of manufacturing frequently different models in the same line will use shared optical components. For example the Leica UV 8x20 and 10x25 appear to have the same eyepiece (and prisms?) but the 10x25 has a larger longer focal length objective lens to achieve the higher magnification (giving a smaller tFOV but the same aFOV due to the same eyepiece). There are many more examples but in many cases two models in the same line with the same objective size may share nearly all optical components except the eyepieces. If the design is optimized for a more popular model (like a 10x50) the prism (and body) size may only be able to illuminate a field stop of the diameter in the 10x50 model. This means that when a longer focal length eyepiece is put on the body for the 8x50 it will have the same field stop diameter thus showing the same total field of view, just a little less "zoomed in" due to the lower focal ratio.
Hope this makes sense and helps.
First one must understand that the magnification is the ratio of the objective lens and eyepiece focal lengths. As you increase the objective lens size, so do the focal lengths (binoculars typically operate with f/3 to f/5 objectives, anything faster results in a poorly corrected image and larger can get quite long! For example an f/10 objective in a 50mm binocular would result in a pair about 2 feet in length). Thus, in order to achieve a focal ratio of 8x, a 50mm binocular may need an eyepiece with twice the focal length. Well corrected, wide angle, long focal length eyepieces can quite large and unwieldy (for example the pentax xw 40mm, a very nice long focal length eyepiece weighs in over 27 ozs, more than many pair of binos on their own!).
Along the same lines, the total field of view is set by the field stop (and focal length of the eyepiece). The field stop is an aperture in the eyepiece/focal plane of the objective. For a long focal length eyepiece to achieve a wide field of view it must have a wide field stop diameter. Such a large image at the field stop also requires large prisms to carry the light cone to avoid vignetting. In many cases such large prisms and eyepieces are impractical for handheld optical devices.
Another factor may be cost. Large well corrected glass components are expensive, especially for non-spherical lens types often used in wide angle eyepieces. Additionally for ease of manufacturing frequently different models in the same line will use shared optical components. For example the Leica UV 8x20 and 10x25 appear to have the same eyepiece (and prisms?) but the 10x25 has a larger longer focal length objective lens to achieve the higher magnification (giving a smaller tFOV but the same aFOV due to the same eyepiece). There are many more examples but in many cases two models in the same line with the same objective size may share nearly all optical components except the eyepieces. If the design is optimized for a more popular model (like a 10x50) the prism (and body) size may only be able to illuminate a field stop of the diameter in the 10x50 model. This means that when a longer focal length eyepiece is put on the body for the 8x50 it will have the same field stop diameter thus showing the same total field of view, just a little less "zoomed in" due to the lower focal ratio.
Hope this makes sense and helps.
tenex
reality-based
Actually FOV is often unimpressive in 42mm models because the manufacturer is trying to keep them a bit smaller than they really should be (viz. Leica), so a common pattern is that 32s have the best FOV and 42s the worst, with 50s somewhere in the middle -- the exception being the sort of 8x50 that you mentioned (or 7x50 or even 7x42), which are even worse for reasons explained above by has530. (The other general trend is that at a given size, higher magnifications often tend to have wider AFOV.)
You will see exactly the same field and its contents; the whole thing will just be smaller at 8x with more black space around it, as yarrellii illustrated. The apparent field is roughly 8 * 6.7 instead of 10 * 6.7.
You made me go out and look at the moon through my 10x32 Ultravid just now...thank you!
If I understand your question, you are asking why Leica doesn’t use an eyepiece with a larger AFOV in their 8x50, so that it has a larger TFOV than their 10x50. If so, I believe the answer is that a larger prism would required, which would require a larger body to house the prism. Otherwise the prism would effectively be stopping down the aperture to something less than 50mm.
Am I glad Leica designed the 8x50 as they did. I first thought that with the relatively narrow FOV, the 8x50 could never be an attractive proposition. I couldn't have been more wrong....
This is of course a personal thing, but the 8x50 UV HD with its extremely "calm", color saturated image has given me the most relaxing viewing experience ever (and I have quite a few other binos to compare).
Based on what I read in an earlier thread (Leica 8x50 Ultravid HD Plus), I seem not to be the only person feeling that way.
Canip
brocknroller
porromaniac
Yes, more complex formula requiring ciphering with tangents and co-tangents, which takes into consideration the amount of pincushion or AMD, there was a thread on this recently.I remember this used to puzzle me as well, I assumed that an 8x (any 8x for that matter) would produce a magnification and render an image comparable to any other 8x (in terms of what you see), and so on with 10x, etc. The explanation is very simple (excuse the lack of technical terms, no aspiration whatsoever, just a desire to help).
You probably know how in the movies the "1st person view" of someone looking through binoculars is two circles joined together, while anyone who has ever actually used binoculars has experienced that what your eyes actually see is a circle, you probably know what I mean. So, let's take that "circle", that's the image you see. Any 8x will show things magnified similarly (although things like apparent field of view or the fact that the binoculars are Porro or roof can alter your personal perception of magnification, but that's another story). So, a 6,7º 8x and a 8,8º 8x will show things magnified 8 times, but the second has a much larger field of view (FOV) which, being both binoculars 8x (same magnification) will produce a larger apparent field of view (AFOV). I've made a simple sketch to help you visualize it.
When you look at something, like the loquat tree in my garden, what you see is trapped inside that "circle of image" we've mentioned. Well, to help you grasp this concept, I actually want you to focus on what is "outside" of that circle where the image is. You've probably experienced, that the image has a round limit (called "field stop"), and everything beyond that point is black. Well, using the example of the 8x50 and 10x50 Ultravids, both having 6,7º FOV, the "amount of black" around the image will appear bigger on the 8x (or, to put it in other words, the circle of image will appear smaller), while on the 10x there will be "less black" around the circle of image, the circle of image will appear larger, it will fill your eyes.
The field of view our eyes see is somehow an ellipse, but the image you see through the binoculars is like a circle inside your field of view. Have a look at this: same image, same "actual" field of view, different "apparent" field of view.
View attachment 1507854
This is the reason many people prefer binoculars with larger AFOV, and 10x are typically good at this, and many people prefer it. Not only do they get more resolving power (although many times this is negated by the increased shake), but they also get "a bigger picture", and that can bee addictive, everything it's more "in your face". If you read binocular reviews, you'll probably come across people referring to binoculars with big AFOV as having a "window view", implying that you get an immersive image, like you were not using binoculars. On the other hand, you will read people referring to looking through binoculars with a small AFOV as peering through a keyhole or a straw.
AFOV can be calculated in degrees, there is a quick (but not exact way) simply by multiplying magnification by actual FOV in degrees, like @andytyle says, 53.6º for the 8x and 67º for the 10x. However, then there is a more complex formula to get the actual figure. Depending on the country (if I remember correctly, I'm happy to stand corrected), beyond 60º (or was it 65º?) of AFOV is considered "wide angle". Some people find a figure in this region of 60º to be pleasing, and going below 55 or 50º to be too compromised, but YMMV.
I hope this helps
But if you look through two bins, you don't need a Texas Instruments calculator to tell which one has the wider AFOV. For example, the 8x42 EDG and 8x32 EDG have virtually the same TFOV (7.7* and 7.8*, respectively); however, the 8x42 EDG has a larger AFOV since it has significantly more pincushion whereas the 8x32 has little pincushion.
OTOH, the 8x42 has more distortion and some astigmatism at the edges compared to the 8x32, which is sharp to the edge. Neither shows "rolling ball" while panning like Swaro SVs, which stretch the FOV and edge sharpness.
There are always trade-offs. For me, it was less about which had the larger AFOV than which had the better ergomomics and weight, which made me choose the 8x32 EDG over the 8x42.
Brock
The 8x50 vs. 10x50 has the same benefits of the 7x42 vs. 8x42. The comfort of bigger exit pupil, more DOF, less shaking, etc, etc.
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