ultravid 8x20 DoF?? (1 Viewer)

takitam · Dec 11, 2008

Hello
I'm new to this forum, learned a lot here, and after trying out some binos, I've found out that for me top quality compacts are better than mid-priced full-size binos like Vortex Viper or Swift 828. I've had Nikon hgl 8x20 for a few days, but decided to return it (that was before trying the big Vipers), which turned out to be good, because now I'll order 8x20 hgl's again and Leica's ultravid 8x20 and keep one which will be better for my eyes. I liked Nikon's depth of field and field flatness very much not to mention the sharpness, so when I tried Vipers 8x42 their depth of field and sharpness were quite dissapointing.

Can anyone tell me if small Leica's have similar DOF to the Nikons?? The closest focusing distance is 2.4m for the Nikon's, 1.8m for the Leica's, I'm asking because I've read somewhere than closer focusing distance equals shallower DOF, is that true?

elkcub · Dec 12, 2008

Hi Takitam,

Welcome to BirdForum.

You might wish to review the most recent thread dealing with DOF.
http://www.birdforum.net/showthread.php?p=1354555#post1354555

Yes, it is true that it is shallower at closer focusing distances.

Best wishes,
Ed

takitam · Dec 12, 2008

Thanks for the link.

What I meant by giving numbers of minimal close focus; 1.8m for Leica, 2.4m for Nikon was how it affects observable Depth of Field (regardless of scientifical validity of this term) in general, not at those distances precisely.

I didn't know there is such confusion regarding the term DoF, but this really doesn't change what I saw: When I focused Nikon 8x20 hgl's on a car ~10m away from me, I could still see objects ~40m away also in focus. With Vortex Viper 8x42 when I focused on a car ~10m away from me, even objects ~20m away were out of focus.

My question is: can anyone who compared Nikon hgl 8x20 to Leica Ultravid 8x20 tell me if they perceived similar DoF with both binoculars. I found out that DoF is an important feature for me.

Thank you

ceasar · Dec 12, 2008

This is an unscientific guess on my part, Takitam; but could the difference have been caused by the relative sizes of the exit pupils of the 2 binoculars (2.5mm vs 5.2mm) and the effect of the brightness of the daylight on the size of the pupils of your eyes? I don't know if it would have an effect but on a dark overcast day, your pupils could open up to 5mm but if you were using the 8 x 20 you would only be getting a 2.5mm cone of light and with the 8 x 42 the cone of light reaching your pupil would be 5mm.

I don't know if this "stop down" factor has the same effect on one's eyes for depth of field as it would have on a camera lens. Maybe someone can elaborate on this?

Bob

elkcub · Dec 12, 2008

ceasar said:
...
I don't know if this "stop down" factor has the same effect on one's eyes for depth of field as it would have on a camera lens. Maybe someone can elaborate on this?

Bob

Bob,

The eye's pupil does operate like the diaphragm of a camera lens, and determines the working aperture of the system. Like a camera, DOF increases as pupil diameter decreases, i.e., as the system is "stopped down."

It can be shown that the combined focal length of the eye plus an afocal telescope is the focal length of the eye itself. The only change when using a telescope, then, is that the DOF of the combined system becomes the eye's normal DOF scaled by the effective magnification of the instrument. If the working distance is the near focus of the instrument, then effective magnification is at a maximum and DOF is at a minimum.

Can anyone tell me if small Leica's have similar DOF to the Nikons?? The closest focusing distance is 2.4m for the Nikon's, 1.8m for the Leica's, I'm asking because I've read somewhere than closer focusing distance equals shallower DOF, is that true?
takitam is offline Report Post

As the near focus decreases there is a disproportional (nonlinear) loss in DOF. The only way to compare the two binoculars, therefore, is to focus both instruments to the same working distance.

I'm not a believer, however, that one can measure optical DOF in a telescope-binocular by observation. The reason is that the observer's eye is actively changing its focal length and aperture by accommodation and pupil response. These are both involuntary biological processes that directly affect what he is trying to estimate. This little conundrum is called "the observer effect."

Be that as it may, side by side comparisons are always worthwhile and encouraged, whatever the reason for observed differences.

Hope this helps.

Ed

Surveyor · Dec 12, 2008

Takitam, Elkcub;

I have both the LXL and Ultravid. I just ran a very uncontrolled test to try to give you some idea about your question.

I used two sample distances one about 330 meters and one about 27’ from me. I started with outside focus and carefully focused in until the far target just came in focus, left the setting alone and tried to find the close focus point. From the far target it came close to 31 m from me for both units. Using the same procedure inside at close distance, both units appeared to have about the same defocus 5.5 feet from the far target. Estimating the amount of defocus is, at best, very subjective, I know. Takitam, to me, the DOF appears very similar, but this is not a very controlled test.

Ed, this may give you some data to confirm your paper. I tried my best to keep eye pupil >3mm and both these distance indicates roughly 2-diopter depth of field. Since my accommodation is only about 2.5D on a good day, I think this is directly in line with your paper.

Best
Ron

elkcub · Dec 13, 2008

Thanks, Ron.

That's an interesting way to go about it, at least as a rough approximation. A procedural factor that might influence the results is whether you focus on the target from near to far, or visa-versa. I'd recommend near to far to create the least amount of accommodation during the process (the eye relaxes). This would also allow maximum accommodation from the target position, but as you mentioned the amount would vary with the individual. I have only about 1.5 diopter capability, if that. Of course, as you also mentioned, judging equivalent amounts of defocus might also be somewhat sloppy, er, subjective.

A similar way to go about it, might be based on a technique Henry Link mentioned some time ago, having to do with evaluating relative magnification. In this application, place two artificial stars at known distances, and focus on the distant one. For two binoculars of the same magnification, the size of the defocus disk of the near star should be smaller if the instrument has greater DOF. I use little glass balls in sunlight to keep the pupil < 2.5 mm. Otherwise, compacts have the advantage.

Also try the test with different magnifications, to see that magnification really has the only reliable effect.

I tried to develop a procedure for measuring blur disk size, but I got worried about hurting my eyes. Too many persistent afterimages.

Ed

Surveyor · Dec 13, 2008

Hi Ed,

I did focus from closer than the close target through it just until the far target came to sharp focus.

To aid in the long distance check when I got an idea of the close point of the range I placed 4 white priority mail boxes at various points close to my near target point then returned to the bino (it was on a tripod) and picked the best focused box and moved the others nearer to it and again picked the best average focus. The range for was from 30 to 32 meters, hence the 31-meter call. The shorter test was done by lining up book spines to check the text with both units.

Back when Henry was working with that test I also tried it, but a slightly different method. I used a collimator to set the infinity focus and then tried to compare the defocused size of a ball bearing about 3.5 m away. I tried this with two 6x, five 8x and two 12x bins and, as near as I could judge the defocused diameter in the field of view, the diameters were consistent with the power between instruments. Again a subjective estimate of size.

I ran this check just, primarily, to answer the question about the LXL's and Ultravids.

Have a good night.
Ron

takitam · Dec 13, 2008

Thank you very much for your answer Surveyor. I'm happy to hear that depth of field is similar for both bins. I think I've read every thread on the net about these two 8x20 binoculars but haven't tried the Leica yet. Small Nikons were great and I'm sure Leicas will be great as well.

As you have both bins can you tell your impressions about pros and cons of each (If you already have, sorry!)? Which do you prefer and why?

Edit: What is the material under the eyecups on Leica, when the eyecups are twisted up? On nikon it is metal, hope its the same with leica.

takitam · Dec 13, 2008

For people w Leica Ultravid 8x20bl what do you think about its leather case functionality in the field? Does it have a 'snap' top open or is it zipped all the way around? Sorry for my english, can't find a better way to describe what I mean.
Thank you

Surveyor · Dec 13, 2008

Hi Takitam;

The Leica have pull out eyecups, they just snap into position fully extended or fully collapsed and, as near as I can tell, are hard plastic fitted with a soft rubber ring.

I prefer the Ultravids to the LXL’s. The Ultravids are a little more compact and ergonomically more to my liking. I do not like the focus control on the objective end of the bino.

The optics are very comparable with, in my opinion, the Leica being just a little more color neutral.

http://www.birdforum.net/showpost.php?p=1352991&postcount=5

I have a BL also but do not use the clamshell case. I never used the case but seem to remember that it opened about 30 degrees and do not remember how it fastened. I replaced all the 8x20 cases with the older thin leather cases that are more compact for pocket use or use zip-loc bags to further reduce the bulk. I think Alexis Powell uses this case.

Have a good day.
Ron

Alexis Powell · Dec 13, 2008

takitam said:
For people w Leica Ultravid 8x20bl what do you think about its leather case functionality in the field? Does it have a 'snap' top open or is it zipped all the way around? Sorry for my english, can't find a better way to describe what I mean.
Thank you

The Leica eyecup under the rubber bit is plastic. I find Leica's eyecups more durable overall than Nikon's, which can have problems with rubber deterioration if not carefully maintained.

As for the clamshell BL case, I like it fine. It is fairly hard, so it protects the bino well in packing. It is held together by a snap (no zipper), so it is not perfectly sealed against sand/water (though the two sides do interlock slightly). The two sides are tethered together, so the clamshell doesn't open up all the way, just enough to easily put the bino in.

--AP

ThoLa · Dec 13, 2008

takitam said:
For people w Leica Ultravid 8x20bl what do you think about its leather case functionality in the field? Does it have a 'snap' top open or is it zipped all the way around? Sorry for my english, can't find a better way to describe what I mean.
Thank you

Looks like this: (see pics)
But there's a nylon bag for the non-leather version which you might purchase as an extra.

Cheers, Tom

takitam · Dec 13, 2008

Thank you very much for your input , you all have been very helpful:t:

Bob, sorry for not replying earlier- I must say I only know that the higher the aperture number in a camera(smaller 'hole' in the lens), the wider depth of field so it's probably the same with binos, as elkcub pointed out. As I use binoculars during daytime mostly, possible improvement of DoF in dusk conditions from 8x42 bins is of no importance to me. Besides, apart from better DoF Small Nikons were clearly sharper than big Vipers. I know I'm stating this again, but I was really surprised about it, in a positive way.

ultravid 8x20 DoF?? (1 Viewer)

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takitam

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elkcub

Silicon Valley, California

takitam

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ceasar

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elkcub

Silicon Valley, California

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The more I understand, the more I understand why I

elkcub

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The more I understand, the more I understand why I

takitam

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takitam

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Surveyor

The more I understand, the more I understand why I

Alexis Powell

Natural history enthusiast

ThoLa

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