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Perceived depth of field (1 Viewer)

jules.b

Well-known member
Hello,

I have moved from 10x35 EIIs to 10x32 HG roofs. Both are great, but I didn't get on with the eye cups on the EIIs.

One thing I noticed with them EIIs was the great feeling of depth of field. I am not sure that any more was in focus with the EIIs than the HGs at any one time, but my eyes seemed to be able to change focus within the view, so that if they were focussed on something far away I could look at another, closer part of the image and focus my eyes sharply and easily on it. This is not as evident with the HGs. Any ideas what causes this effect?

Jules
 
jules.b said:
One thing I noticed with them EIIs was the great feeling of depth of field. I am not sure that any more was in focus with the EIIs than the HGs at any one time, but my eyes seemed to be able to change focus within the view, so that if they were focussed on something far away I could look at another, closer part of the image and focus my eyes sharply and easily on it. This is not as evident with the HGs. Any ideas what causes this effect?
Hello Jules,

I also have the 10x32HGs and can confirm that the perceived DOF is very shallow. I can think of at least four potential explanations for this:

1) the HGs have a "flat field" eyepiece whereas the EIIs have slightly curved focus plane. If you look at the bird on the tree, the vegetation on the ground may be more in focus with the "non-flat field" eyepiece.
2) the focuser of the HG is smooth and over-sensitive: a small touch and the image is out of focus.
3) the eyepiece of the HG seems to be corrected so that the image looks good (IMO) only when the eye pupil is on the optical axis. Move the eye a little and chromatic etc. aberrations reduce sharpness.
4) the 10x35s may be slightly brighter and having a wider FOV they bring more light in the eye. This may cause the iris to stop down more with the EIIs and increase the eye's DOF (don't know whether this is significant).

Best regards,

Ilkka
 
I cannot comment on this particular comparison. However, I noticed a similar effect when comparing the Nikon Action 7x35 with the Nikon Action EX 7x35. The Action model seems to have a better depth of field as I can focus on an object at "midrange" and yet still have some close range objects in sharp focus as well as some very distance objects. The EX version doesn't quite match that same quality. The eyepieces are totally different though the rest of bins' specs are quite similar.
 
I agree. My 10 x 35 EII's have great DOF, as do my 8 x 30 EII's which have much better DOF than my 8 x 32 LXL's.
Bob
 
Jules,

Here is a somewhat different interpretation.

jules.b said:
Hello,

I have moved from 10x35 EIIs to 10x32 HG roofs. Both are great, but I didn't get on with the eye cups on the EIIs.
I returned a very nice 8x30 E2 to EO for the same reason. Eyecups too darn wide.

One thing I noticed with them EIIs was the great feeling of depth of field. I am not sure that any more was in focus with the EIIs than the HGs at any one time, but my eyes seemed to be able to change focus within the view, so that if they were focussed on something far away I could look at another, closer part of the image and focus my eyes sharply and easily on it. This is not as evident with the HGs. Any ideas what causes this effect?
Yes, most likely you are experiencing the 3-D spatial depth perception associated with porro prism binoculars. Technically, this is not depth of field, which is a monocular property of the optics. Spatial depth perception results from the objective lenses being wider apart than your eyes, somewhat offsetting the effect of magnification that gives you a sense of greater object size. What you have described is very typical of viewing 3-D photographs, namely that the observer can "look around" within the scene. The scene, of course, is in your head.

This interpretation doesn't refute earlier comments, but I think it's most likely to be the primary explanation for your observations.

Ed
PS. More and more I use porro prism binoculars because of this depth effect, specifically an 8.5x44 Swift 804ED.
 
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FrankD said:
I cannot comment on this particular comparison. However, I noticed a similar effect when comparing the Nikon Action 7x35 with the Nikon Action EX 7x35. The Action model seems to have a better depth of field as I can focus on an object at "midrange" and yet still have some close range objects in sharp focus as well as some very distance objects. The EX version doesn't quite match that same quality. The eyepieces are totally different though the rest of bins' specs are quite similar.

Yes...
That long eye relief ep comes at an optical price.

Looking at it only from the viewpoint of pure raw optical performance I think the non EX ep is a better optical match to the objectives which, I assume, is identical in both.

The other day I was on my porch focused at infinity watching swallows at a great distance and the wire netting that encloses the porch was very nearly in perfect focus which is only 9 feet away.

SF
 
Spatial depth perception results from the objective lenses being wider apart than your eyes, somewhat offsetting the effect of magnification that gives you a sense of greater object size.
Thanks, never had that explained before. By the way, I like the reverese porros best for some reason.
 
Tero said:
Thanks, never had that explained before. By the way, I like the reverese porros best for some reason.

Tero,

Reverse porros have a lot going for them, particularly low-power configurations like Bushnell's Custom Compacts. Since the objectives are closer together than the eyes, there is a reduction in 3-D spatial depth perception. However, apparent image size becomes greater and somewhat offsets this. Because low-power configurations, e.g., 6x25, 7x26, also have inherently greater depth of focus (again, a monocular property), the combination can be very satisfying.

In the end, porro, roof, or reverse porro, a lot depends on what you get used to. I don't think there is any right or wrong to be found, just interesting explanations.

Regards,
Ed
 
"The other day I was on my porch focused at infinity watching swallows at a great distance and the wire netting that encloses the porch was very nearly in perfect focus which is only 9 feet away."

This is my experience with the EIIs -at least that I can have them focussed on infinity, and move my eyes within the view to focus on something nearer than infinity that was not on focus when I looked to infinity, without re-focussing the binos. Perhaps the 3d effect mentioned by Elkcub eneables your eyes/brain to re-focus?
 
jules.b said:
"The other day I was on my porch focused at infinity watching swallows at a great distance and the wire netting that encloses the porch was very nearly in perfect focus which is only 9 feet away."

This is my experience with the EIIs -at least that I can have them focussed on infinity, and move my eyes within the view to focus on something nearer than infinity that was not on focus when I looked to infinity, without re-focussing the binos. Perhaps the 3d effect mentioned by Elkcub eneables your eyes/brain to re-focus?
Your eyes are allowing you to see at different distances. When focused on a distant object, my left eye can easily adapt to closer objects. My right eye can no longer accomplish the same feat and the disparity between the two is why I truly appreciate high quality optics.

The beauty of the SE, EII and other binoculars with a sharp FOV is that there is less work for the eye to perform as it naturally moves around the image. Dismissing fuzzy edges as unimportant is hogwash, when your eyes no longer accommodate. I'll bet those with restricted eye accommodation are the biggest fans of wide, sharp fields of view.

John
 
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Sout Fork said:
"The other day I was on my porch focused at infinity watching swallows at a great distance and the wire netting that encloses the porch was very nearly in perfect focus which is only 9 feet away."
...

Sout,

I don't know what the near focus of all the Nikon Actions are, but this one is 16.4 ft. http://www.shopping.com/xPO-Action_Nikon_Action_Binoculars. It's hard to believe that you could have seen things at 9 ft. "nearly in perfect focus," — also with them set at infinity.

Ed
PS. Sorry, Jules, and you have been talking about 10x35 E2, which have a short focus of 5 meters = 15+ ft. Basically, I'd make the same statement about them.
 
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The optical setup (how lenses are put together) and the construction of the binoculars also has something to do with depth of field perception. To use 10x as an example, the Swift Kestrel porro 10x50 (marked HR5) has the best depth of field of any 10x i own or looked at, while Nikon EII 10x35, Leica Ultravid, Swarovski EL and SLC 10x42 and 10x50 are all different. I tried focusing all of these at 10 meters and them i looked to see how far and how close i can still see and call it "in focus": There were clear differences.
 
Luca said:
The optical setup (how lenses are put together) and the construction of the binoculars also has something to do with depth of field perception. To use 10x as an example, the Swift Kestrel porro 10x50 (marked HR5) has the best depth of field of any 10x i own or looked at, while Nikon EII 10x35, Leica Ultravid, Swarovski EL and SLC 10x42 and 10x50 are all different. I tried focusing all of these at 10 meters and them i looked to see how far and how close i can still see and call it "in focus": There were clear differences.

Luca,

I basically agree with you. The 10x50 Kestrel HR/5 is a phenomenal binocular, even by comparison to the formidable 10x35 Nikon E, 10x42 SLC, and 10x25 SLC, —which I also own. Of course, it has the largest porro prisms, widest field of view, largest exit pupil, and greatest inter-objective distance — all of which support "depth of field perception..." I don't find it any more difficult to carry around than the 10x42 SLC either.

Ed
 
Luca said:
The optical setup (how lenses are put together) and the construction of the binoculars also has something to do with depth of field perception. To use 10x as an example, the Swift Kestrel porro 10x50 (marked HR5) has the best depth of field of any 10x i own or looked at, while Nikon EII 10x35, Leica Ultravid, Swarovski EL and SLC 10x42 and 10x50 are all different. I tried focusing all of these at 10 meters and them i looked to see how far and how close i can still see and call it "in focus": There were clear differences.
Were you looking on axis at different targets or moving your attention to an object in a different part of the lens? The reason I ask is because I believe razor sharp lenses with wonderfully sized sweet spots (e.g. the SE) naturally convey a strong sense of DOF simply because it takes less eye accommodation to achieve acceptable focus. Move your attention off-axis and all DOF impressions are defined by the character of the so-called sweet spot. If the sweet spot isn't so sweet, I suspect the reported DOF isn't either!

John
 
Does anybody have a 9x40 or so porro bin? I have only found the Nikon reverse porros in 9x. I have been holding off on any 10x50s other than the Barskas, very cheap. Mainly due to the limits you run into at 10x, close focus etc, bulk.

I am not going to carry some 39 0z thing like this
http://www.eagleoptics.com/index.asp?dept=1&type=19&purch=1&pid=4456

Clearly these are more versatile
http://www.eagleoptics.com/index.asp?dept=1&type=19&purch=1&pid=3825

if they only made them in 9x, would be ideal for me.
 
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Tero said:
Does anybody have a 9x40 or so porro bin?....

Hi Tero
If you don't mind used binos, Opticron used to make a 9x35 Minerva and Swift used to make a 9x42 SPWA (I think I've got that right). Now and then the Swift turns up on eBay but I've yet to see the Minerva 9x35. Both worth picking up if the price is right. I have the Opticron 8x40 Minerva and it's a beautiful small porro with a mono-bloc body casting. Field of view is quite narrow by modern standards but the view is crisp to the edge.

Good luck with the search for 9x. I think a lot of people would buy a high quality 9x and perhaps it would end all the '8x or 10x ?' discussions ;)

Cheers
John
 
John Traynor said:
If the sweet spot isn't so sweet, I suspect the reported DOF isn't either!

John

You are right about that.

I did try to look only through the middle of the field of view (i.e., keep my eyes in the sweet spot only).

I was trying to say that magnification is not the only factor influencing depth of field perception.
 
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