Depth Of Field better when diameter is larger? (2 Viewers)

[Trinovid]

"As a conclustion we can state that the depth of focus that an observer can achieve with his binocular, depends mainly on his ability to accomodate, the magnification of the binocular and to a lesser degree on the diameter of the effective exit pupil."

Hey thanks!

As for the Japanese one; “Other than the first word, I can’t understand that at all. Oh well…”

 

[Trinovid]

Is Latin allowed?

Yeah, of course. All the birds got Latin names!

 

[Maljunulo]

I give up.

I’m out.

 

[Scott98]

I have a Swaro SLC 8x42 and a Zeiss Terra 8x25 and found the DOF of the 8x42 way better.

I've noticed the same thing - the bigger the aperture, the more DOF at the same magnfication

 

[Tringa45]

This seems like a weird technical contrarian hill to try to die on but I'll give it one more go explaining why the question doesn't even make sense without considering the user (and thus the exit pupil).

What is depth of field? A simple definition would be something along the lines of "The range of distances for which objects can be brought into acceptable focus". The key here is "brought into acceptable focus". This begs two questions. Brought into focus where? And brought into focus how? Binoculars are inherently afocal instruments meaning they broduce no net convergence or divergence of the optical beam. This means binoculars don't actually bring anything into focus, the image is formed by the users eyeball. Brought into focus where? Or rather where is the focus measured? Well that would be the imaging plane, or in the case of visual optical instruments...the retina of the user!

The difference from user to user in perceived depth of field is accounted to their own visual accommodation (how much they can focus their eyeballs) but even without any visual accommodation (changing the focal length of the eye) depth of field will be different for different entrance pupil sizes which in the case of binoculars is controlled by the exit pupil/objective diameter (until your exit pupil exceeds the entrance pupil dilation). You can try this on your own by punching a bunch of small holes of different sizes in a peice of paper, looking at an object at infinity and holding some text much closer to your face then looking through. The smaller the hole the more in focus the two objects will appear simultaneously (that is until diffraction comes into play...).

Well, it would be possible to quantify DoF, but I agree that it wouldn't make much sense.
Köhler (or was it König?) stated that a 3,4 arcminute circle of confusion would be perceived as a point source by most observers.
Consequently, if a binocular were adjusted for theoretical focus on a point source (coincidence of objective and eyepiece focal planes) at some arbitrary distance (10 m?), then one could define the range of distances inside and outside of focus which would produce circles of confusion of 3,4'.
However, whatever the distance chosen it wouldn't be very relevant to practical binocular use and it suffices to know that magnification is the overwhelming factor affecting DoF.
As already explained, accommodation plays a very minor role and I don't think exit pupil is very relevant either. In poor lighting the 2,5 mm exit pupil of an 8x20 would stop down dilated eye pupils and theoretically improve perceived DoF, but under these conditions you're not going to recognize much detail through an 8x20 and I'd rather use my 8x56.

John

 

[tenex]

I have a Swaro SLC 8x42 and a Zeiss Terra 8x25 and found the DOF of the 8x42 way better.

Perhaps it's time to return to the original question. There is no theoretical reason why this would be the case, so we should ask how exactly you're judging DOF. Can you describe a certain scene observed with both, what you've focused on, which other elements seem sharp or don't, how far they are, etc? (Bear in mind that other factors may be involved too, for example field curvature reducing the area of best sharpness, so try to line elements up and do your DOF comparisons fairly close to the center.)

 

[bsantini]

Actually, yes. Since your eye’s pupil will routinely be smaller than a large objective’s exit pupil, your eye is, in effect, stopping down the objective in situations like these, which can help contribute to an enhanced depth of field.

B

 

[henry link]

I've long used a testing method that involves the use of point sources of light in the form of artificial stars to judge the size of circles of confusion directly rather than trying to infer DOF from how "sharp" objects appear to be outside the plane of best focus.

Tested that way the circles of confusion shown in all binoculars of the same magnification will be the same size as long as the exit pupil is larger than the eye's pupil. If the exit pupil is smaller than the eye's pupil then the exit pupil aperture determines the eye's effective aperture and focal ratio and therefore its DOF. Only under that condition will the aperture of the binocular have any effect on DOF.

 

[bsantini]

The statement I made is fact using a focal system like a binocular or telescope.
When the eye’s entrance pupil is smaller than the system's exit pupil, there is a stopping down of the aperture.
But the light seen at that eye pupil size is as much as can be at that magnification.

 

[Tringa45]

The statement I made is fact using a focal system like a binocular or telescope.
When the eye’s entrance pupil is smaller than the system's exit pupil, there is a stopping down of the aperture.
But the light seen at that eye pupil size is as much as can be at that magnification.

A binocular or telescope is afocal! You have misunderstood the workings of a Keplerian telescope. Focus is achieved on the viewer's retina.

John

 

[tenex]

As daylight pupil size will surely be under 3mm, it should not affect the OP's comparison of an 8x25 and 8x42 at all, and as previously remarked it wouldn't create an impression of greater DOF in the larger instrument in any case.

(And for those who may have missed Barry's self-introduction: Hello!)

 

[Tringa45]

(And for those who may have missed Barry's self-introduction: Hello!)

Alas not the first newcomer, who knows it all better than Henry.

 

[bsantini]

A binocular or telescope is afocal! You have misunderstood the workings of a Keplerian telescope. Focus is achieved on the viewer's retina.

John

Sorry. Autocorrect Typo.
I Meant to write afocal

Alas not the first newcomer, who knows it all better than Henry.

hi
I really don't want to come off that way. But I do have some training and creds to back up my thinking
For 28 years, I was product and sales manager for Teke Vue Optics, and a regular presenter at Stellafane.
Let continue the discussion

 

[Trinovid]

Alas not the first newcomer, who knows it all better than Henry.

Alas, not the first time a thread was going along nicely and you had to take it in a negative direction.

 

[Tringa45]

Sorry. Autocorrect Typo.
I Meant to write afocal

hi
I really don't want to come off that way. But I do have some training and creds to back up my thinking
For 28 years, I was product and sales manager for Teke Vue Optics, and a regular presenter at Stellafane.
Let continue the discussion

If that was a typo, then I take that back. However your post #29 appeared to contradict Henry Link, a long-standing member, who has contributed more to the understanding of optics on this forum than any other.
Nevertheless, DoF is a property of the binocular and any perceptual differences at the same magnification are either very minor or imagined.

John

 

[Tringa45]

Alas, not the first time a thread was going along nicely and you had to take it in a negative direction.

And on this thread that was your 5th post devoid of relevance or content.

 

[Trinovid]

And on this thread that was your 5th post devoid of relevance or content.

Your lack of self awareness is absolutely astonishing as you call others out for less egregious behaviors than you do routinely, especially in these two most recent triply irrelevant examples.

 

[jeanluc125]

Hello

I have several pairs of binoculars, the DOP between my canon 10x30is and my Swarovsky NL Pure 10x32 does not seem very different.
On the other hand I found that my Zeiss Dialyt 8x30B have more DOP than my Swarovsky Habicht 8x30 (DV), difference between PORRO and ROOF ?
I also compared my Swarovsky Habicht 8x30 with my ZEISS Jena Detrintem 8x30, both PORRO type, without perceiving a significant difference ?
Comparing my Zeiss Dialyt 8x30B with my LEICA Ultravid 8X20, which are both ROOF, I don't see any real difference in DOP.
Hopefully I could contribute ....

Jean-Luc

 

[jeanluc125]

J'ai aussi remarqué des différences de DOP avec les mêmes jumelles,
que ce soit avec mon NL Pure 10x32 ou mon ZEISS Dilalyt 8x30B que j'utilise le plus souvent, selon l'ensoleillement, plus il y a de lumière, plus mes pupilles rétrécissent et plus j'obtiens de DOP. C'est très important pour moi.

 

[jeanluc125]

in english: (excuse me...)
I also noticed differences in DOP with the same binoculars,
whether with my NL Pure 10x32 or my ZEISS Dilalyt 8x30B that I use most often, depending on the sunlight, the more light there is, the more my pupils shrink and the more DOP I get. This is very significant for me.