Depth of Field - I am confused (1 Viewer)

[Paultricounty]

I do not contest the results and I do not find something offensive in your post.

I am out of this thread.

Lol, I was just having some fun with ya. Truly no offense intended, don’t leave 😁 ✌🏼🙏🏼

 

[elkcub]

Psychophysics is an interdisciplinary branch of Psychology and Physics. Depth-of-Focus is a psychophysical term. As stated in the second article attached:

..., the eye exhibits a certain tolerance to out-of-focus images, a feature that is known as depth-of-focus (DOF). The corresponding distance range in which the objects are seen ‘‘clearly’’ is known as depth-of-field (DOFi).

It should be evident, however, that since each observer must have a unique, subjective perception of DOF, the phrase "subjective DOF" is an oxymoron, and the phrase "true/real DOF" is a fiction.
Ed

 

[Trinovid]

Ted (post # 94), are you saying that Henry is wrong?

No, he’s just saying that Henry is not qualified and simply another “opinion” and that he “will search my self on Internet".

 

[tenex]

I cannot understand the point of continual references to subjectivity, psychophysics, etc on this topic. We are talking not about different individuals' perceptions using the same instrument, but the other way around.

 

[Paultricounty]

Psychophysics is an interdisciplinary branch of Psychology and Physics. Depth-of-Focus is a psychophysical term. As stated in the second article attached:

It should be evident, however, that since each observer must have a unique, subjective perception of DOF, the phrase "subjective DOF" is an oxymoron, and the phrase "true/real DOF" is a fiction.
Ed

Thank you

 

[Maljunulo]

If someone were to take the autofocus module from a camera and monitor its output voltage, couldn’t that voltage be used to approximate an “Index of Fuzziness”?

 

[Canip]

No, he’s just saying that Henry is not qualified and simply another “opinion” and that he “will search my self on Internet".

Okay, fair.
But in his place, I would search where I most likely will get the right answer (I know science is not in favor these days, but I trust this is a temporary thing and reason will return to humans before long), Holger‘s book or Köhler‘s mentioned by Hermann are a good starting point. At least when we discuss optics.

 

[Trinovid]

I know science is not in favor these days, but I trust this is a temporary thing and reason will return to humans before long

Actual science has always been in favor, still is, and most of the supposition of lack of support of it has come from people in support of nonscientific claims.

I think quite highly of Hermann and his knowledge and thought it would be obvious from my wording that what the other poster had said was ridiculous on the face of it. He wouldn’t listen to someone who knows what he’s talking about and would rather trust some other random source from the internet to place his trust.
There are varying levels of pot stirrers here, but treating Hermann as a random know-nothing really takes the cake.
Ridiculous, among a wide range of other descriptors.

 

[Maljunulo]

Nonsense will always triumph over science, because science takes hard work to understand, requires a certain level of general knowledge, and demands the ability to think in a disciplined and linear fashion.

Those traits are not uniformly distributed.

 

[tenex]

Nonsense will always triumph over science because the first principle of science is too unattractive. It is humility: awareness of what one doesn't know, and how easily one may misunderstand. Francis Bacon wrote all about this in 1620 (Novum Organon) but it's too often ignored, leading to the recent disaster with "following the science" that seems to have discredited science itself in some quarters.

I can't tell whether this is in agreement or disagreement with either Trinovid or Canip; the tragedy is that it has come not to matter anymore. Scientific thinking was never really going to catch on.

 

[Scott98]

Those traits are not uniformly distributed.

well you're starting with a bell curve so half the people are dumber than average....right out of the starting gate. Add in a deliberate campaign of scientific illiteracy from the corporate media, compulsory public school methods that fail for many people, and it only goes downhill from there!

 

[Maljunulo]

I could never understand how anyone, who had ever been inside a library, could ever think they knew very much.

 

[Trinovid]

I could never understand how anyone, who had ever been inside a library, could ever think they knew very much.

LoL! Nice!

 

[looksharp65]

I cannot understand the point of continual references to subjectivity, psychophysics, etc on this topic. We are talking not about different individuals' perceptions using the same instrument, but the other way around.

Simply because vision is inherently a form of perception, and, as such, subjective. In my first post in this thread I showed how visual acuity, a highly individual trait, may affect the perceived DOF in similar ways as the level of magnification does.
An afocal instrument like a binocular does not contain the property 'depth of field' since an observer is involved, and the observer's powers will have the greatest impact on how they perceive the DOF.
The term 'depth of field' is nonsensical without an observer, and even more so because binoculars [roughly] can be used in one single manner.

The other possible way to use a pair of binoculars or a scope - digiscoping, either with line pair targets or with diffraction circles, mean that the virtual image delivered through the instrument is focused to a real image on a sensor, would theoretically show the depth of field with regard to magnification and dioptrical defocus, but such a result is still purposeless since everyone asking about DOF actually refers to perceived DOF.
In this regard, depth of field shares a common trait with colours - neither exists, unless in the observer's consciousness.

//L

 

[Maljunulo]

Oh boy it sounds like we’re getting close to politics again.

We weren’t, until your post.

 

[dries1]

Post #102 and #115 are what one should read and try to understand.

 

[Trinovid]

Post #102 and #115 are what one should read and try to understand.

Maybe I was tired when I read his first one, but #115 was much easier to follow and is now causing me to think of this subject in a different light. Thanks for pointing these posts out for reexamination.

 

[has530]

I think another thing that might be confusing people when trying to evaluate on their own is how much is in focus at the same time vs. how much they can visually accommodate at a set focus position. I haven't tested this but I would suspect that if the optics are poor and there is a lot of astigmatism or spherical abberation it may be more difficult to refocus with just your eyes leading to less perceived depth that can be brought into focus without touching the focuser. I have also considered the non-circular defocused points as a possible reason the pentax FB-8 are so darn finicky with their square objectives.

 

[Holger Merlitz]

Simply because vision is inherently a form of perception, and, as such, subjective. In my first post in this thread I showed how visual acuity, a highly individual trait, may affect the perceived DOF in similar ways as the level of magnification does.
An afocal instrument like a binocular does not contain the property 'depth of field' since an observer is involved, and the observer's powers will have the greatest impact on how they perceive the DOF.
The term 'depth of field' is nonsensical without an observer, and even more so because binoculars [roughly] can be used in one single manner.

The other possible way to use a pair of binoculars or a scope - digiscoping, either with line pair targets or with diffraction circles, mean that the virtual image delivered through the instrument is focused to a real image on a sensor, would theoretically show the depth of field with regard to magnification and dioptrical defocus, but such a result is still purposeless since everyone asking about DOF actually refers to perceived DOF.
In this regard, depth of field shares a common trait with colours - neither exists, unless in the observer's consciousness.

//L

In principle, once we got the raw numbers, it is possible to calculate the range of distances in which the image appears in focus to the observer. We need the accommodation width of that observer, the diameter of the effective exit pupil (the smaller one of both, the exit pupil and the eye pupil), and the magnification. Acuity plays a role, indeed, since it defines the circle of confusion that is tolerable to the individual observer, but this is eventually a minor effect because the observer will always use his accommodation to get the object sharp, or else he would have to re-focus by a tiny amount. A reduction of the tolerable circle of confusion would require just a minor refocusing of the instrument with little influence on the actual range of the sharp image.

Now, the width of accommodation of a given individual is not necessarily a fixed quantity, but dependent on his state of exhaustion, on the presence of drugs such as coffee or alcohol and on general health conditions, perhaps on the ambient temperature (the eye lens is less flexible in freezing temperatures). Then, the DOF is defined at the center of field, since off-center aberrations would affect image sharpness. In particular field curvature can create that 'vary-focal' effect that allows off center objects in the foreground to be sharp even though they are technically outside the DOF. The observer then believes to experience an enhanced DOF and draws incorrect conclusions.

It is a difficult business, and the repeated discussions on this topic reflect these difficulties. In real life applications, however, there is little to worry about: Just remember that low magnifications significantly enhance the DOF, and that in some situations a strong field curvature can be exploited to use the vary-focal effect if you want to survey the landscape from your observation site.

Cheers,
Holger

 

[Canip]

Glad you stepped in, Holger - it was about time!😉