It was the Vanguard Endeavour EDII 8x42 I'd used in the other tests. It's the only modern 8x I currently have at the moment.
David
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Canon 8x25 IS brief test (1 Viewer)
- Thread starter Binastro
- Start date
It was the Vanguard Endeavour EDII 8x42 I'd used in the other tests. It's the only modern 8x I currently have at the moment.
David
Some 'ballpark' figures:
---human acuity (well illuminated) is usually around 60 arc-seconds
---30 arc-seconds is rare but has happened
So, 10-power with 6 arc-seconds actual (60 apparent) resolution would be the limit for most people
(as far as what the thing has to do)
3 arc-seconds actual would be the point past which no-one can tell.
That said, I have seen airplane details lower than that myself.
I'm guessing larger detail can actually be guessed at to finer detail than point seperation,
assuming the cortex is doing a sort of line-fit or curve-fit.
If you want to see if the instrument resolves finer than your eye can use, use a static
target, mount, and a low-powered monocular at the eyepiece. I found a 6x does OK,
though a 2x or 4x multiplier is brighter and less fussy.
---human acuity (well illuminated) is usually around 60 arc-seconds
---30 arc-seconds is rare but has happened
So, 10-power with 6 arc-seconds actual (60 apparent) resolution would be the limit for most people
(as far as what the thing has to do)
3 arc-seconds actual would be the point past which no-one can tell.
That said, I have seen airplane details lower than that myself.
I'm guessing larger detail can actually be guessed at to finer detail than point seperation,
assuming the cortex is doing a sort of line-fit or curve-fit.
If you want to see if the instrument resolves finer than your eye can use, use a static
target, mount, and a low-powered monocular at the eyepiece. I found a 6x does OK,
though a 2x or 4x multiplier is brighter and less fussy.
I think I need to clarify some stuff.
I suppose most will have heard of 20/20 vision (though it is usually referred to as the metric 6/6 in Europe). It is the upper limit for what is regarded as 'normal' vision. Statistically most people do a bit better than this, though of course not everyone. The eye test chart that everyone will be familiar with has specially designed letters or patterns that differ by 1/5th of the height and width. The size of that 1/5th is calibrated for the reading distance. On the 20/20 line of the chart that difference creates an angle to the eye of 1/60th of a degree which is usually referred to as an arcminute or 60 arcseconds. A small percentage of people will have eyesight twice as good as 20/20 which would be 20/10. There have been very rare examples of individuals recording 20/8.
What is very confusing is that the one arcminute standard used by the eye docs for the resolution, or acuity of the eye is not the same measurement used by everyone else when measuring resolution. If you use stars, MTF or the line charts we tend to use here, the results are numerically a factor of two greater. So 20/20 becomes 2 arcminutes or 120 arcseconds and 20/10, 1 arcminute or 60 arcseconds.
The first three sets of comparisons I reported here used a USAF 1951 line chart, and I was testing the effect of shake on the detail I could see. So testing my eyesight or apparent acuity. The best result was 60 arcseconds (20/10) though this was with two eyes which is usually a bit better than the single eye figures your eye doc would give you. I also listed the resolutions for the binoculars with the objective stopped down to 20mm. The magnification was boosted with another binocular for that measurement.
The last report was an attempt to replicate the observation made by Binasto. Although I calculated the size of the spots as an angle, the results should not be compared to the other studies in any way. Seeing a single feature is quite different from resolving two or more spots or lines, though highly dependant on contrast and other factors. About the 'biggest' star you can see in the sky is Betelgeuse and that is 0.05 arcseconds or an angle 150 times smaller than the smallest spot I was using and you don't need a binocular to see that.
David
I suppose most will have heard of 20/20 vision (though it is usually referred to as the metric 6/6 in Europe). It is the upper limit for what is regarded as 'normal' vision. Statistically most people do a bit better than this, though of course not everyone. The eye test chart that everyone will be familiar with has specially designed letters or patterns that differ by 1/5th of the height and width. The size of that 1/5th is calibrated for the reading distance. On the 20/20 line of the chart that difference creates an angle to the eye of 1/60th of a degree which is usually referred to as an arcminute or 60 arcseconds. A small percentage of people will have eyesight twice as good as 20/20 which would be 20/10. There have been very rare examples of individuals recording 20/8.
What is very confusing is that the one arcminute standard used by the eye docs for the resolution, or acuity of the eye is not the same measurement used by everyone else when measuring resolution. If you use stars, MTF or the line charts we tend to use here, the results are numerically a factor of two greater. So 20/20 becomes 2 arcminutes or 120 arcseconds and 20/10, 1 arcminute or 60 arcseconds.
The first three sets of comparisons I reported here used a USAF 1951 line chart, and I was testing the effect of shake on the detail I could see. So testing my eyesight or apparent acuity. The best result was 60 arcseconds (20/10) though this was with two eyes which is usually a bit better than the single eye figures your eye doc would give you. I also listed the resolutions for the binoculars with the objective stopped down to 20mm. The magnification was boosted with another binocular for that measurement.
The last report was an attempt to replicate the observation made by Binasto. Although I calculated the size of the spots as an angle, the results should not be compared to the other studies in any way. Seeing a single feature is quite different from resolving two or more spots or lines, though highly dependant on contrast and other factors. About the 'biggest' star you can see in the sky is Betelgeuse and that is 0.05 arcseconds or an angle 150 times smaller than the smallest spot I was using and you don't need a binocular to see that.
David
Last edited:
Hi David,
I took photographs of that pimple first in poor light, which was unsatisfactory and then on a bright day where the exposure was 1/1000 second at F/5.8 at ISO160. -1/3 stop correction. I was using a 30 times optical zoom and four times digital zoom which gives about 2800 mm equivalent focal length (35mm).
The pimple is not the best shape, it is a triangle approximately as seen, but the base slopes at an angle of 15°.
There are two chimney pots I use, one at 124 m and the other at 117m. It is the 117m one that I'm using here.
Anyway the calculations suggest that the area of the pimple is the same as a square pimple that subtends an angle of 17 arc seconds, so your memory was better than mine.
I will check my calculations later to make sure that I have not made any mistakes.
Regarding the Easy Jet observation that you made, it is a great observation as are all yours and Kimmo's careful measurements.
However, the observations I made and the observations of the EasyJet that you made are quite different.
Had I seen my aircraft again, and had I been looking for the name on the side of the fuselage or the tail it is a quite different observation to the discovery observation that I made.
The discovery observation is an observation of the unknown, which is not the same as observing something that you are looking for and is known.
In birdwatching, it may be that most of the observations are of known objects. The bird is large in the binocular and then you look for detail which you know maybe there.
As I mentioned earlier, a discovery with a 16 inch telescope is then visible in a 10 inch telescope and later in a 6 inch telescope.
There are enormous differences between observations of the unknown and the known.
In addition, the great observations that you are making and the measurements are in optimum conditions, both in lighting conditions and generally.
But in the real world lighting conditions are often not perfect, and one may be somewhat tired etc.
My observations over many years suggest that the difference between a tripod mounted binocular or image stabilised binocular and standard handheld binocular are much larger than 40% for a 10 times binocular, probably about a 70% to 80% improvement.
And at night,the improvement with my 18×50 between handheld unstabilised and stabilised is between 100% and 200%.
I will recheck my calculations tomorrow all being well.
I took photographs of that pimple first in poor light, which was unsatisfactory and then on a bright day where the exposure was 1/1000 second at F/5.8 at ISO160. -1/3 stop correction. I was using a 30 times optical zoom and four times digital zoom which gives about 2800 mm equivalent focal length (35mm).
The pimple is not the best shape, it is a triangle approximately as seen, but the base slopes at an angle of 15°.
There are two chimney pots I use, one at 124 m and the other at 117m. It is the 117m one that I'm using here.
Anyway the calculations suggest that the area of the pimple is the same as a square pimple that subtends an angle of 17 arc seconds, so your memory was better than mine.
I will check my calculations later to make sure that I have not made any mistakes.
Regarding the Easy Jet observation that you made, it is a great observation as are all yours and Kimmo's careful measurements.
However, the observations I made and the observations of the EasyJet that you made are quite different.
Had I seen my aircraft again, and had I been looking for the name on the side of the fuselage or the tail it is a quite different observation to the discovery observation that I made.
The discovery observation is an observation of the unknown, which is not the same as observing something that you are looking for and is known.
In birdwatching, it may be that most of the observations are of known objects. The bird is large in the binocular and then you look for detail which you know maybe there.
As I mentioned earlier, a discovery with a 16 inch telescope is then visible in a 10 inch telescope and later in a 6 inch telescope.
There are enormous differences between observations of the unknown and the known.
In addition, the great observations that you are making and the measurements are in optimum conditions, both in lighting conditions and generally.
But in the real world lighting conditions are often not perfect, and one may be somewhat tired etc.
My observations over many years suggest that the difference between a tripod mounted binocular or image stabilised binocular and standard handheld binocular are much larger than 40% for a 10 times binocular, probably about a 70% to 80% improvement.
And at night,the improvement with my 18×50 between handheld unstabilised and stabilised is between 100% and 200%.
I will recheck my calculations tomorrow all being well.
Binastro,
Last thing first. I agree that at night, but also in deep twilight, differences in favor of a stable image are much greater still than in good light. In very low light, if there are no points of light in the view, I even struggle to focus the binocular unless it is stable.
In good light, my guess is that as soon as the task is, as you say, detection of unknown detail, or if it is reading of unknown text, the differences again are greater than they are in our simple trial of trying to resolve the line orientation of a well known and precisely located target.
Kimmo
Last thing first. I agree that at night, but also in deep twilight, differences in favor of a stable image are much greater still than in good light. In very low light, if there are no points of light in the view, I even struggle to focus the binocular unless it is stable.
In good light, my guess is that as soon as the task is, as you say, detection of unknown detail, or if it is reading of unknown text, the differences again are greater than they are in our simple trial of trying to resolve the line orientation of a well known and precisely located target.
Kimmo
Binastro,
I'll take your point about the easyJet being a known target. Even though the previous three aircraft didn't have tail letters and nearly all the fuselage letters were obscured by the wing at my viewing angle. I could tell at a glance that one started Y another KA and the third S but that's hardly a test. I suppose those letters are a couple of meters tall so even at 2.5miles (4km) that's not much of a challenge. I'll look out for a better target to convince you.
David
I'll take your point about the easyJet being a known target. Even though the previous three aircraft didn't have tail letters and nearly all the fuselage letters were obscured by the wing at my viewing angle. I could tell at a glance that one started Y another KA and the third S but that's hardly a test. I suppose those letters are a couple of meters tall so even at 2.5miles (4km) that's not much of a challenge. I'll look out for a better target to convince you.
David
. Thank you Kimmo and David.
David, regarding reading the aircraft letters, the whole point is that you were looking for letters to read.
When I was looking at the aircraft, I was definitely not looking for letters or a name.
When I pressed the stabiliser button of the 2014 build Canon 8×25 IS the name ETIHAD magically appeared in large letters which had colour. This rather amazed me as it was so easy to read that I could not believe that I'd missed it without the stabiliser. But with the stabiliser off I actually could not read it probably because it was moving and I had to track the aircraft.
I think that you are both doing excellent work in measuring and quantifying the results with and without a tripod and with the stabiliser and a Finnstick.
Also observations are very personal and mine are mainly non-bird related. I'm usually panning with the binocular, which also highlights the difference between a stabilised and non-stabilised binocular.
David, I'm not really happy with the photographs of that pimple as it is at the limit of the camera I was using and there is some irradiation at the edges. At a later date I hope to take better photographs with a more capable camera or perhaps using a telescope.
Incidentally, today when I was out in the street I saw a protected unaided eyes sunspot, which I estimated as 39 arc seconds penumbral diameter. It took about eight seconds to see and confirm it. I suspected it probably after three seconds.
It was favourably placed though just below centre disc. Seeing protected unaided eyes sunspots near the Sun's limb is very difficult because of crowding.
Nowadays, when my eyes are tired I cannot see fine detail but today my eyes were rested.
David, regarding reading the aircraft letters, the whole point is that you were looking for letters to read.
When I was looking at the aircraft, I was definitely not looking for letters or a name.
When I pressed the stabiliser button of the 2014 build Canon 8×25 IS the name ETIHAD magically appeared in large letters which had colour. This rather amazed me as it was so easy to read that I could not believe that I'd missed it without the stabiliser. But with the stabiliser off I actually could not read it probably because it was moving and I had to track the aircraft.
I think that you are both doing excellent work in measuring and quantifying the results with and without a tripod and with the stabiliser and a Finnstick.
Also observations are very personal and mine are mainly non-bird related. I'm usually panning with the binocular, which also highlights the difference between a stabilised and non-stabilised binocular.
David, I'm not really happy with the photographs of that pimple as it is at the limit of the camera I was using and there is some irradiation at the edges. At a later date I hope to take better photographs with a more capable camera or perhaps using a telescope.
Incidentally, today when I was out in the street I saw a protected unaided eyes sunspot, which I estimated as 39 arc seconds penumbral diameter. It took about eight seconds to see and confirm it. I suspected it probably after three seconds.
It was favourably placed though just below centre disc. Seeing protected unaided eyes sunspots near the Sun's limb is very difficult because of crowding.
Nowadays, when my eyes are tired I cannot see fine detail but today my eyes were rested.
Hi Guys, I am new to this forum, not a birding enthusiast yet but I became interested in binoculars over the past year. So I tried out everything from an old Swift Audubon to a Nikon 8x32 SE and an Oberkochen 10x50. Now I own a Canon 8x25 IS, 10x30 IS and the 10x42 L IS. I agree with Kimmo the Canon 10x42 is one of the best, but for the size, weight and price I really like the 8x25 IS. I think it is underrated - my sample is very sharp, has better edge-to edge field than my 10x30, and less CA. My 8x25 is made in Japan and stabilizes instantly, no delay. And to me the further advantages over the 10x30 are that it has a plastic body not prone to sticky rubber syndrome, it is lighter and smaller than the 10x30. I just wanted to add my experience of the 8x25 to those wondering which compact IS binocular to choose. BTW has anyone compared the Canons with the Kite Optics IS models - are the Kites optically inferior?
