8x30/32 porro suggestions? (1 Viewer)

[Binocollector]

Sorry, I thought it was a little unclear - I'm no native speaker.
So an example - Henry stated that a small exit pupil would step down the pupil of the eye, therefore increase its focal length and increase DoF in low light if the eye's pupil is larger than the exit pupil of the bino.
That would mean, a 10x25 would have greater DoF if your eye's pupil was dilated to 4mm compared to a 10x40. That would mean that magnification is not the only factor to determine DoF.
And the post from a German astronomy forum I linked claimed that a bino that delivers more light to the eye, therefore decreasing the entrance pupil of the eye because it contracts, would increase DoF by the same mechanism that Henry described.
Not sure I'm making myself clear.

 

[Ted Y.]

Ted Y,
What are the two binoculars do you have in 8x32 and 8x42 (maybe I missed it)? Have you tested the magnification to see if they are very close ? One could be 7.8 and the other 8.2, which could make a difference for those who might be able see any difference there.

Im wondering if we’re talking about the same line from the same maker. If we’re not then there are so many factors that can give you a perception of more or less DOF.

Paul

The magnification is not verified. It is good idea, but I do not know how to do it in a reliable way for so small differences.
One binocular is Steiner, the other one is Fujinon.
I can compare the 8x32 Steiner one with another Steiner, 8x42, but not the same model.

"If we’re not then there are so many factors that can give you a perception of more or less DOF." This means the DOF depends on so many factors.

Or maybe FOV is something not depending on the human observer nor of the presence of an observer and some Apparent/Relative/Subjective FOV exists and changes for each observer?

 

[Paultricounty]

The magnification is not verified. It is good idea, but I do not know how to do it in a reliable way for so small differences.
One binocular is Steiner, the other one is Fujinon.
I can compare the 8x32 Steiner one with another Steiner, 8x42, but not the same model.

"If we’re not then there are so many factors that can give you a perception of more or less DOF." This means the DOF depends on so many factors.

Or maybe FOV is something not depending on the human observer nor of the presence of an observer and some Apparent/Relative/Subjectiv FOV exists and changes for each observer?

It would be nice to know the models of each of your binoculars. There is perceived DOF and actual DOF, if I understand it correctly. Magnification is the main ingredient for DOF. I have multiple binoculars in 7x , 8x , even a 9x , 10 and 12x magnification. The least DOF is the 12x and the most are the 7‘s. Sometimes binoculars with a curved FOV (Leica Ultravids and classics) can have a tendency to give a perception of more DOF as apposed to binoculars with field flatteners that can give a perception of less DOF.

That’s my understanding. Guys like Herman, Gigi and few others here are to me optical experts , and I generally listen and learn from there advice.

I meant Henry. Sorry Herman. 😉

Paul.

 

[Paultricounty]

The magnification is not verified. It is good idea, but I do not know how to do it in a reliable way for so small differences.
One binocular is Steiner, the other one is Fujinon.
I can compare the 8x32 Steiner one with another Steiner, 8x42, but not the same model.

"If we’re not then there are so many factors that can give you a perception of more or less DOF." This means the DOF depends on so many factors.

Or maybe FOV is something not depending on the human observer nor of the presence of an observer and some Apparent/Relative/Subjectiv FOV exists and changes for each observer?

I got it TedY. I think understand where you were going with that, basically your relating DOF to focal length based on exit pupal.

Paul

 

[Ted Y.]

It would be nice to know the models of each of your binoculars.

Ooops.
Steiner Peregrine 8x32mm, Fujinon HC 8x42mm. I have access to another one, Steiner HX 8x42mm. All are roof binoculars.

 

[henry link]

OK. Waiting for it. Thank you.

Ted and Binocollector,

It's going to be a couple of days before I can get back to this. Sorry for the delay.

Henry

 

[Hermann]

As described in other threads, the phrase "depth of field depends only on magnification" is an urban legend.
I have two 8x binoculars (32 mm and 42 mm) and the difference in depth of field is real. The practice overpower the theory.

In other words, all those studies into the depth of field of binoculars are wrong?

Sorry, that's nonsense.

Check for instance König/Köhler ³1959, Die Fernrohre und Entfernungsmesser, Berlin, Heidelberg, p. 122-125, and Merlitz ²2019, Handferngläser. Funktion, Leistung, Auswahl. Haan-Gruiten, p.155-157 for summaries.

Hermann

 

[Binocollector]

Maybe we should continue this in another thread, there was one just recently and I'll quote Holger:

Holger Merlitz' book "Handferngläser", 1st edition 2013: p. 123: "The depth of field which an observer can attain is primarily determined by the accomodation capacity of his eyes, then also by the magnification of the binocular, and to a lesser degree by the diameter of the effective exit pupil..."

So where exactly does he say that DoF is "only" determined by magnification? Or are we talking about a theoretical DoF without an observer?
Even if we rule out accommodation there still is the phrase "effective exit pupil", so...
I think it's weird that every time this discussion comes up somebody says, 'only magnification determines DoF, except for factors x, y, z.' So do factors x, y, z play a role or not? It can't be that hard to figure out.
Maybe the confusion comes from the difference between a system without an observer and a theoretical DoF that can be measured by optical devices or calculated and the actual use case of a binocular.
The problem I think is the phrase "perceived DoF" which muddies the water and makes it seem like - 'oh, it's only in your head, you're imagining things'. Or would we be able to actually determine these differences by including the eyes as an optical system in some kind of experiment?
The thing is - if we include the 'human factor' like accommodation (which in all those explanations I read is ruled out) or the eye's pupil (which is just as arbitrary to include since our eyes are all different and how far the pupils dilate is basically similar to the difference in the ability to accommodate).
So without any human factor, DoF is always the same between binos with the same magnification - be that 10x25 or 10x50 as per Henry's explanation of afocal instruments (I think I have understood that part) but as soon as a human using the bino comes into play - does 'perceived DoF' mean I could actually 'measure' a difference somehow between different instruments when I include my eyes as part of the optical system? If that would be so - then there can be indeed differences between different binos with the same magnification but different apertures and brightness and a lot of factors come into play.
So why is it 'nonsense' when someone says, 'I see a different DoF between different binos of the same magnification'?
That's what I have difficulties understanding.

 

[elkcub]

All,

We've had several discussions about DOF in the past that could profitably be reviewed. I'll single out THIS HARD TO FINE ONE, since it's embedded (starting on or around post #48) in Henry Link's thread entitled: "The World's Best 8x42: The Zeiss 8x56FL." I've copied the attachment below from post #50, which I proffer as a potentially unifying framework to reconcile what may simply be different observable aspects of DOF.

Ed

 

[Ted Y.]

@henry link

I created this thread DOF = binocular & human for DOF subject.

 

[tenex]

Maybe the confusion comes from the difference between a system without an observer and a theoretical DoF that can be measured by optical devices or calculated and the actual use case of a binocular.

No, the confusion comes from people misconstruing simple statements of fact. "Perceived" just means perceived, not "you're crazy", etc. There is no DOF property in binoculars without an observer because they're afocal, but no one said there was, etc. What we really need here is a new, separate thread on psychology instead of optics.

You can measure the DOF you perceive, but it would help to agree on a standard method (Henry has suggested one).

Edit: For some reason, when someone says "I see more DOF in this 8x bin than that one", threads here never quite resolve that by reference to the factors above: how much more? How different is the magnification, or field curvature? Does brightness differ enough to affect pupil diameter? etc. It would be nice to have a well worked out example but seems too difficult to pull all the information together.

 

[elkcub]

It might also be added that when discussing the DOF of "binoculars" it is easy to lose sight (no pun) of the fact that the concept actually refers to each telescope separately. When the two telescopes are used together as a binocular instrument, many commentators show every indication that they confound the perception of spatial depth with that of depth of field. Long story short, when evaluating DOF paralyze one eye to prevent accommodation, and close the other one to inhibit stereopsis effects.

Ed