The term of Resolution, Micro Contrast, Contrast (1 Viewer)

[dorubird]

The terms of resolution, contrast, micro contrast.
To clarify these terms, here is a brief summary of how I understand and use these certain terms in my evaluation of binoculars or photo lenses:

RESOLUTION: It is also called "Definition".
Resolution it is the ability of an optical system to resolve as many lines as possible per mm (lines=detail). Resolution it is a quantity of details.




CONTRAST: It is also better called "General Contrast".
Contrast it is the ability of an optical system to make easier the general perception of the image, by increase the depth between white and black.







MICRO CONTRAST: It is also better called "Acutance". It only applies in photography, not for visual!
Acutance it is about the transition between edges of a line resolution. Maximum acutance is when the black edges of a resolution line stop suddenly and begin the white space, not being blurred. Acutance it si not the quantity of details (this is the resolution) but in other words, somehow "the quality of details".






SHARPNESS: It is a very general term, used very freely, and used to sum up at least two terms from above:
Resolution+ Micro contrast+ General Contrast = Sharpness
CLARITY/TRANSPARENCY: As well as sharpness, these are very general terms, in a broad sense, also used to sum the constituent terms of sharpness, but only that, in addition, I would add here the Light Transmission.
Sharpness+ Light Transmission= Clarity /Transparency
So Clarity and Sharpness are terms with a broad meaning, used when we want to refer to a general picture, not specific to an optical quality from the three listed above!
For example, we say of the images below that they decrease in sharpness even if they have the same resolution:


Conclusion:
Using these terms, I evaluate my binoculars by myself, comparing them on a resolution chart, with and without booster magnifier, but always corroborated with tests from real life in nature. After these I drawing my own conclusions and my own ranking list. It should not influence you, believing that they are objective tests only because I use a chart resolution, tripod, booster, distance standards, etc... Even so, the degree of subjectivity of my tests remains present, as with any kind of these tests. Of course maybe a lower degree of subjectivity than when I simply looked through binoculars and drew conclusions about the resolution, but still subjective.

 

[Tringa45]

Sorry, but this is a misinterpretation of the facts.
Disregarding overall contrast losses due to veiling glare or internal reflections, the terms contrast and resolution are inextricably intertwined.
One could say they are reciprocals of one another.
Let's assume you are viewing a well-illuminated resolution chart such as the 1951 USAF with increasing line pair frequencies per millimetre.
If the binocular is any good at all you would see no degradation of central sharpness or contrast at its nominal magnification, because its resolution should be much better than that of your own eyes.
To see its limitations you would have to boost the magnification to a value somewhere around that of its objective diameter in millimetres, i.e. >40x for a binocular with 42 mm objectives.
With increasing line pair frequency the contrast would diminish up to a point where you see just a grey blur.
You have then reached the resolution limit of your binocular and knowing the frequency of the last detectable line pairs and the viewing distance you could calculate its resolution in arcseconds.
The diffraction limited resolution in arcseconds of a telescope was defined by Dawes as 116/D, where "D" is the aperture in millimetres.
For a binocular with 42 mm objectives this would be 2,76" but because most binoculars have comparatively fast focal ratios this is never achieved and a value of 4" could be regarded as good. Only astronomical telescopes and the best birding scopes attain the Dawes' limit.
If your binocular shows high contrast at high line pair frequencies it will automatically show high contrast at lower frequencies.
I think the term "micro contrast" is misleading and should be banned.

John

 

[dorubird]

Of course, the micro contrast can only be seen with a booster magnification not naked eye. I use the Leica Ultravid 8x20 as a booster. So my 8x magnification is enough to exceed the resolving magnification of the objectives of any binoculars. (the resolution magnification of an objective is the aperture divided by two). So, for example, with 10x42mm binoculars, the resolving magnification is 21x. With an 8x booster I exceed this value by far. At 80x such magnifications I can see micro contrast differences.
Microcontrast/ acutance is something real. It is not the same as general contrast (See my second graphics with low contrast and high micro contrast/ acutance). That is precisely why I said: "..MICRO CONTRAST: It is also better called "Acutance"..." Because micro contrast it has nothing to do with the general contrast of the image, and not to create confusion.

 

[Tringa45]

(the resolution magnification of an objective is the aperture divided by two). So, for example, with 10x42mm binoculars, the resolving magnification is 21x.

Where did you get that? I've enjoyed you photographic dissections, but that makes no sense at all.
There is no such value as "resolution magnification". The resolution limit of any one objective is a specific value in arcseconds. The magnification required to see it is dependent on the tester's eyesight.
If that 42 mm binocular could resolve 4" (line pairs) that would be a single line of 2". If you had 20/20 vision you could resolve 1 arcminute and would need >30x magnification to see the resolution limit of the binocular.


John

 

[dorubird]

Where did you get that?

From astronomy documentation! It is a term use in astronomy. In romanian we call "grosisment rezolvant" in english maybe "resolving magnification". Objective diameter/2= resolving magnification of objective

 

[Tringa45]

From astronomy documentation! It is a term use in astronomy. In romanian we call "grosisment rezolvant" in english maybe "resolving magnification". Objective diameter/2= resolving magnification of objective

Lost in translation or someone who didn'know what he was talking about?
It's generally acknowledged that one needs a magnification upwards of the numerical objective diameter in millimetres to see the resolution limit.
When measuring the resolution of my 65 mm and 88 mm scopes I used a 3,5 mmeyepiece for magnifications of 130x and 140 x respectively.
The results were 1,78" and 1,41" respectively, i.e. at and close to the Dawes' limit.

 

[tenex]

Microcontrast/ acutance is something real. It is not the same as general contrast

Acutance is defined as a property of an image like a photograph, and therefore also a result of everything that recorded and printed the image. How could an optical system alone deliver more or less "microcontrast" independently of contrast and resolution? You can illustrate conceptually what such a difference might look like using simple images, but you're not actually going to find binoculars of comparable contrast and resolution with a visible difference in "microcontrast", and their combined effect is already understood as "sharpness".

 

[dorubird]

Tringa45, tenex,
Yes, you are right! I borrowed the term acutance/micro contrast from photography, and I wrong extrapolated from photography to visual. So for visuals (binoculars) we can only talk about resolution or contrast when it comes to sharpness, micro contrast being a term only for photographic images. I will make corection in the definition of the term "microcontrast"