Optics misused Terminology. (1 Viewer)

[Troubador]

In my opinion, resolution is explained here: Image resolution - Wikipedia
Resolution like in 'screen resolution', printer 'resolution'.

For sharpness, the first part of this article: https://www.photoreview.com.au/tips/shooting/sharpness-acutance-and-resolution/
Please note I do not agree with the point of view of the article about resolution.

Resolution can be measured objectively.
'Sharpness' is the ease with which fine details can be perceived by the human eye and involves some subjectivity especially since human eyes are not all the same.

 

[Maljunulo]

“Sharpness” can be increased with edge enhancement.

Beginning microscopists often stop the sub stage diaphragm down much too far, because it makes the image “sharper”.

 

[Binocollector]

The reason nobody gave definition of all the terms is that nobody wants to be the one to go first and get his definitions destroyed by the crowd . I already had a post ready but then thought, "nah, I'd rather not. Half of my definitions would be wrong anyways." I don't think it reflects on the wider subject of academia .

 

[dries1]

Apologies Henry, happy Memorial Day.

 

[Binastro]

Even something like weight or mass cannot be defined absolutely.

Similarly aperture and diameter.

However aperture is defined as the clear aperture of the objectives.
But hold on, the real aperture is defined by the field stops, prism size and shape and the result is not even circular.

Diameter is easier as it is traditionally the diameter of the objectives removed from the cell.

As to resolution.
As I have said repeatedly, the resolution of the unaided eyes, varies from the 0.57 arcsecond that Barnard could see as the diameter of a wire seen against the sky, to the several arc minutes that the average good sight can resolve double stars without optical aid.
This is a range of 200 times or so for resolution, which people here consider a scientific fixed term.
It isn't.
They talk about 1 arc minute, but this is false. It depends what resolution you are talking about.
I could resolve epsilon Lyrae naked eye stars from town. But many can't. It is 3.5 arcminutes separation.

People waffle on about Dawes limit when discussing resolution completely divorced from its actual meaning.
The separation of two white 6th magnitude equal stars as seen with a 6 inch high quality refractor by Dawes and his experienced friends, in dark skies.

Definitions with regard to binoculars are not a fixed quantity.
People happily use 8x30, knowing it means 8x magnification and 30mm aperture.
The real value might be 6.7x and 27mm, which is sort of nearly acceptable.
But then someone suggests, Oh no it should be 30 divided by 8.

A list of definitions regarding binoculars is probably a personal list and not an absolute list.

I talked of object glass to howls of derision, saying it is a centuries old term.
All my friends know what it means.
It means objective.
So, now I only use objectives to conform with the U.S. members here.

Blooming means coating.

Why on earth people talk of fields in feet at 1000 yards, I don't know?
But they know what it means.
To me it is just weird.
A field is 8.2 degrees, I don't need another definition.

Unfortunately, definitions here on this forum will probably not succeed.

Regards,
B.

 

[Maljunulo]

Weight varies with the local gravitational field …….. mass does not.

 

[Binastro]

But how do you define mass?

By the standard kilo in Paris or by newer methods involving spheres costing millions hand polished by an ex Zeiss employee in Australia who came out of retirement.

We get nearer to exact definitions but will never get there absolutely.

Napoleon demanded an exact measure of length.
The metre was defined as 10 million metres from equator to pole.
However, the surveyor got it slightly wrong and I think Napoleon demanded the ultimate price for this poor gentleman.

The Greeks got a pretty good measure also.

This doesn't matter for binoculars, but people expecting perfect definitions won't get them.

Some definitions are merely poetic descriptions.

Regards,
B.

 

[elkcub]

I’ve noticed over and over how many of us either misused or overlap our optical description terminology. I know I’ve been guilty as charged. Some things like resolution and light transmission can be measured and are not subjective. Other things are completely subjective like sharp and clear, and other things are border line like warm or cold.

Maybe some can give their definitions of the following , and ad to the list.

Resolution:
Transmission:
Transparency:
Brightness:
Clarity:
Sharpness:
Immersive:
Stereoscopic:
Distortion:
Globe effect/rolling ball:
Neutral:
Warmness:
Cold:

Binoculars are opto-mechanical visual instruments, so these and many other terms fall into one of three broad categories:

I. Mechanical Design: monocular, binocular, prisms, coatings, materials, weight, balance, volume, ...
2. Optical-physics:
System: magnification, transmission, field-of-view, eye-relief, clear aperture, exit pupil, coatings, ...
Image: airy pattern, diffraction, distortion, contrast, ...
Color: luminosity, dominant wavelength, excitation purity ...
3. Psycho-physics:
System: stereopsis, spatial perception, apparent field, effective pupil size, ...
Image: resolution, space, clarity, relative distance, gradients, depth of field, immersiveness, movement illusions ...
Color: brightness, hue, saturation, color contrast, neutral, warm, cold, ...

Categories 1 and 2 items can be measured "objectively" without reference to personal observations or opinions. Manufacturers often make mistakes in stating these facts. Category 3 items can often be measured "objectively" when reference to a "standard human observer." However, most folks rely on personal observations, often accompanied by a strong "expert observer syndrome."

Ed

 

[Ted Y.]

What is

excitation purity

?

 

[has530]

To add to the original topic the one term that really "grinds my gears" is transmission. As someone who works extensively in spectroradiometry in my day job, I spend a lot of time worrying about the transmission spectra of various optical components. To hear people say "such and such binocular has a 96% transmission" or "such is brighter than other because A has a transmission of 89% and B is 92%" is nonsensical to say the least. Even if we ignore any questions such as how much of a difference can humans perceive the meaningfulness of such statements us dubious at best. To give any one number for the transmission does not make any sense because the transmission is wavelength dependent. It may transmit 96% of photons st 531 nm but I would bet good money it isn't transmitting much in the far IR. Additionally when comparing binoculars against each other I am personally rather skeptical of various numbers for transmission floating around that people use. How was the light coupled into the binocular? What "white" light source was used as the reference for the transmission spectrum? What about the setup changed between coupling the light directly to the detector and coupling it through the binoculars? How were the uncertainties calculated and propagated? These measurements are certainly interesting but I think deserve a healthy bit of skepticism, especially when comparing between different binoculars measured by different people.

But how do you define mass?

By the standard kilo in Paris or by newer methods involving spheres costing millions hand polished by an ex Zeiss employee in Australia who came out of retirement.

We get nearer to exact definitions but will never get there absolutely.

The kilogram is actually exactly defined since 2019 in terms of the Planck constant, the speed of light and hyperfine transition frequency of 133Cs ((299792458)2/(6.62607015×10e−34)(9192631770)hΔνCs/c2).

 

[Maljunulo]

But how do you define mass?

By the standard kilo in Paris or by newer methods involving spheres costing millions hand polished by an ex Zeiss employee in Australia who came out of retirement.

We get nearer to exact definitions but will never get there absolutely.

Napoleon demanded an exact measure of length.
The metre was defined as 10 million metres from equator to pole.
However, the surveyor got it slightly wrong and I think Napoleon demanded the ultimate price for this poor gentleman.

The Greeks got a pretty good measure also.

This doesn't matter for binoculars, but people expecting perfect definitions won't get them.

Some definitions are merely poetic descriptions.

Regards,
B.

The kilogram does not “define” mass, it establishes a standard unit of measurement of a property of matter.

 

[has530]

The kilogram does not “define” mass, it establishes a standard unit of measurement of a property of matter.

I believe based on their message about spheres or the old standard in paris this is what they were talking about. As for defining mass, it is a property of matter and is well defined depending on the context in which you are using it (inertial vs. gravitational vs relativistic etc). As for the origin of mass, or what gives matter mass...we don't know! I am not up to date on all the latest models and their workings as I am and experimentalist, not a theoretical physicist.

 

[Paultricounty]

Binoculars are opto-mechanical visual instruments, so these and many other terms fall into one of three broad categories:

I. Mechanical Design: monocular, binocular, prisms, coatings, materials, weight, balance, volume, ...
2. Optical-physics:
System: magnification, transmission, field-of-view, eye-relief, clear aperture, exit pupil, coatings, ...
Image: airy pattern, diffraction, distortion, contrast, ...
Color: luminosity, dominant wavelength, excitation purity ...
3. Psycho-physics:
System: stereopsis, spatial perception, apparent field, effective pupil size, ...
Image: resolution, space, clarity, relative distance, gradients, depth of field, immersiveness, movement illusions ...
Color: brightness, hue, saturation, color contrast, neutral, warm, cold, ...

Categories 1 and 2 items can be measured "objectively" without reference to personal observations or opinions. Manufacturers often make mistakes in stating these facts. Category 3 items can often be measured "objectively" when reference to a "standard human observer." However, most folks rely on personal observations, often accompanied by a strong "expert observer syndrome."

Ed

Thx Ed that’s good stuff. 🙏🏼

 

[elkcub]

What is

?

To quote from the attached article, "...excitation purity is a well defined, quantitative measure of the saturation of a particular color." Also see the introduction.

All of the psycho-physical measures are based on a 'standard human observer' and can be assessed for any telescope with a properly measured transmission spectrum as described in the attached article. Note that day and night "brightnesses" are the integrals of the measured transmission curve weighted by the photopic (day) or scotopic (night) curves. Photopic and scotopic refer to the state of adaptation of the standard observer's retina.

Ed

 

[Ted Y.]

To quote from the attached article, "...excitation purity is a well defined, quantitative measure of the saturation of a particular color." Also see the introduction.

All of the psycho-physical measures are based on a 'standard human observer' and can be assessed for any telescope with a properly measured transmission spectrum as described in the attached article. Note that day and night "brightnesses" are the integrals of the measured transmission curve weighted by the photopic (day) or scotopic (night) curves. Photopic and scotopic refer to the state of adaptation of the standard observer's retina.

Thank you.
Something new for me.
I like the idea of "standard human observer".

 

[kimmik]

I'd like to add a parameter to the original list, that is not well known but is a deciding factor for me when choosing bino:

Etendue per mass, also known as light throughput per mass.

A binocular with high etendue per mass is the equivalent of a car with high power to weight ratio.

Another parameter is angular moment of inertia.

 

[Maljunulo]

I'd like to add a parameter to the original list, that is not well known but is a deciding factor for me when choosing bino:

Etendue per mass, also known as light throughput per mass.

A binocular with high etendue per mass is the equivalent of a car with high power to weight ratio.

I presume this is quoted in photons per second per gram, from an agreed upon spectral line of an agreed upon intensity.

I suggest either the green Mercury or the green Hydrogen line, and we can haggle over the intensity.

 

[has530]

Another parameter is angular moment of inertia.

Uh oh, incoming debate about the optimal hand position for particular models do maximize the angular moment while minimizing torque for the steadiest view (you could easily maximize the moment by holding onto just the eyepieces but I think everyone agrees this would not steady the view). Also how much of the shake is from rotational vs translational jitter? Also the wider the spacing of the barrels (ie porro vs roof) the greater the moment along that axis but also the greater the torque your hands will exert from shaking! I feel as though this could be it's own thread on its own (especially since I haven't heard anyone misuse angular moment of inertia).

 

[kimmik]

Totally lost me there I’m afraid 😂