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Why does my 15x60 seem less sharp? (1 Viewer)

tenex

tenex

reality-based
Today I was contemplating a classic binocular, a Zeiss (West) 15x60 GAT* porro from the late 1980s, already with better oculars and coatings than the original 60s model. Alpha glass back then, its view is wide, bright, and quite nice. There's no sense of strain due to miscollimation, and of course I adjusted the diopter. But what I immediately notice is that things don't exactly seem to snap into focus, and it's not just because the travel is rather long, though it is. As I hunt, at no setting does even the center of the field ever seem to get quite as crisp or sharp as I've come to expect today. (I know there was a still later "B"GAT* model of this 15x60; did it improve on this performance, or only provide greater eye relief for glasses?)

Large objectives are supposed to offer higher resolution. So can anyone explain what this sense of less sharpness is, and why? Are the coatings not providing as much contrast as modern ones? Is it some assortment of minor aberrations that are better corrected today, with such a cumulative effect?
 
[email protected] said:
Modern binoculars are sharper because of improved coatings and better quality ED glass.
Click to expand...

No, that's not correct. The Zeiss is a porro, as far as resolution is concerned it should be as sharp as it gets. Even the old versions of the 15x60 dating back to the time before multi-coatings were introduced were as sharp as it gets sharp. Heck, even old porros *without* any coatings were sharp. And decent porros don't require any ED glass, providing the focal length of the objectives is sufficient to get rid of any CA. It's only roofs with focusing lenses between the objective and the eyepieces that do.

Four possible explanations:

[1] There's something wrong with the binocular.

[2] Binoculars with high contrast seem to be sharper than binoculars with low contrast. However, if that 15x60 is a "T*" model, I don't think that should be of any real significance. Even the first versions of the T* coatings introduced in the late 1980s were already pretty good.

[3] Often binoculars with high magnifications seem less sharp than binoculars if used handheld, simply because the handshake makes them look less sharp. This is particularly true because at 15x magnification a binocular requires much more careful focusing than a binocular with lower magnification.

[4] Any atmospheric disturbances (like warm air rising in the sunshine) and/or any dust in the air may make a binocular with higher magnification seem less sharp than one with lower magnification. In the right conditions even an 8x binocular may seem sharper than a 10x binocular.

I think (3) or (4) are the most likely explanations here.

Hermann
 
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tenex said:
Today I was contemplating a classic binocular, a Zeiss (West) 15x60 GAT* porro from the late 1980s, already with better oculars and coatings than the original 60s model. <snip> (I know there was a still later "B"GAT* model of this 15x60; did it improve on this performance, or only provide greater eye relief for glasses?)
Click to expand...

There were basically three versions of the 15x60. The first two were basically the same, except that the second version ("GAT*") had multilayer coatings and was rubber armoured. They both share the same Erfle eyepieces that were most definitely unsuitable for people who need glasses. The difference between these two versions is quite striking; the coatings *do* make a rather clear difference in actual use, even though both versions were definitely "sharp". But the difference in contrast is quite obvious.

The third version had "B"-eyepieces, making them suitable for eyeglass wearers ("BGAT*"). Many people will feel the third version is easier to use than the first two versions with their (very) short eye relief. However, I don't think the third version is any "better" than the second version - if, and only if, you can deal with the short eye relief.

I actually quite like the first version, despite their lower contrast. But the first version was noticably slimmer and lighter than the rubber armoured second and third versions, making them easier to use handheld. BTW, the production of the first version started in 1958, so it's one of the series of great Zeiss porros that included a 6x30, 8x30, 7x50, 8x50 and 10x50.

Hermann
 
I agree with you that higher magnification and atmospheric disturbances can make a binocular seem less sharp especially handheld. But I still think the increase in contrast provided by modern coatings increases the apparent sharpness. I think that is what Tenex is observing. I had several generations of the Nikon 8x32 SE and the models with the more updated coatings appeared sharper to my eyes. I have had older porro's and they are sharp but they don't appear as sharp as modern binoculars because their contrast isn't as good. Sharpness is edge contrast. From Tobias's excellent review.

http://www.greatestbinoculars.com/allpages/articles/mtf/mtfmysteries.html
 
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I think you got this absolutely right Hermann.

I would only add that at 15x the depth of field is much narrower than the 8x and 10x with which we are more familiar, so necessarily more of the view really is out of focus. Add hand-shake and atmospherics and you have a fine 'wobbly view' cocktail.

Lee
 
I'll second Hermann's and Lee's comments. I have the 7x50 B/GA T* and its sharpness of image even when compared to more modern 7x50's is highly noticeable and really quite amazing.
 
I agree with Arthur.

A good cleaning often helps. Over the years we have read lots of comments about how much brighter and sharper their binocular is after somebody had Swarovski (usually it is a Swarovski) clean it.

Bob
 
You could eliminate #3 and #4 on Hermann's list by tripod mounting the binocular and examining a sharpness target indoors or not too far away outdoors.

I think it's likely there is something "wrong" that would be revealed by a high magnification star test. I have three old Zeiss Porros (6x30, 8x30B and 10x50). All of them star test poorly. I don't have time now to go into detail about the defects that vary among them, but the common fault in all six telescopes, even by the loose standards of binocular optics, is excessive spherical and chromatic aberration. The patterns are so similar that I have to conclude that the thing they all have in common, the air spaced tele-objective design, is at fault.

To a certain extent this is the story with most binoculars. Optics that are mediocre to poor when objectively tested are rendered visually acceptable by low magnification and by the eye's pupil accepting rays from only the central part of the objective lens in daylight, the latter especially beneficial to large exit pupil/low magnification binoculars like 7x50s. I haven't seen any of the 15x60 versions, but I would be very surprised if their star tests look any different, and more than the other models they are stuck with the aberration revealing disadvantages of relatively high magnification and small exit pupils.
 
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Just looked briefly with single coated 1960s 15x60 Zeiss.
These were completely overhauled and cleaned by Zeiss.

Dull day.
Image not bright.
Main lack of sharpness is hand holding.

Minimal false colour on axis, but dull late afternoon in winter.
Some false colour near the edge.
Pincushion distortion pronounced.
Curved field, sharp at edges when refocused.

My eyes a bit tired.

So must repeat on a sunny day and star test at night.
But previously I have thought this to be a very good binocular.

It was much brighter than the Canon 18x50 IS.
 
4mm EP in the Zeiss versus a 2.77mm EP in the Canon. A lot of difference. All the Canon's are not real bright because of their smallish EP except for 10x42 IS-L. How is the contrast and resolution on the Zeiss compared to the Canon?
 
Hermann said:
Four possible explanations:
[1] There's something wrong with the binocular.
[2] Binoculars with high contrast seem to be sharper than binoculars with low contrast...
[3] Often binoculars with high magnifications seem less sharp than binoculars if used handheld, simply because the handshake makes them look less sharp...
[4] Any atmospheric disturbances (like warm air rising in the sunshine) and/or any dust in the air may make a binocular with higher magnification seem less sharp than one with lower magnification...
Click to expand...

Thanks, I've been trying to figure out why it's been so long since I used this Zeiss. It was mainly #3, and perhaps also some #2 and #4 (in warm winter sun over snow). As soon as I put them on a tripod I got the great view I wanted. Even a monopod helps tremendously. I wasn't sure what was going on because somehow my idea of hand-shake was a sharp image that just jumped around until steadied better. But beneath that really obvious motion there must be a subtler level of unsteadiness, even when I think I'm doing pretty well, that gives an impression of unsharpness. I didn't understand that clearly before.

The problem with this Zeiss is it really begs to be handheld, and seems built for that. I suppose that would work well for any practical purpose, spotting game or whatever, but when I just want to admire the view it's not going to be ideally sharp. I presume the same would be true of any 15x.

Also, I have a simple tripod adapter that may not be the most convenient, as the bino has to be upside-down, requiring reversing the diopter and leaving less room for the nose. Are there better ones?
 
[email protected] said:
Sharpness is edge contrast. From Tobias's excellent review.
Click to expand...

He mentions something else that may be relevant: a design difference between the 32mm Leica I'm used to, which emphasizes "micro"contrast more, and this Zeiss. I think I may also see this, looking (as I was yesterday) at bare tree branches in the distance. But at least that's a minor thing, not so frustrating.
 
Troubador said:
I would only add that at 15x the depth of field is much narrower than the 8x and 10x with which we are more familiar, so necessarily more of the view really is out of focus.
Click to expand...

Yes, this may also have been part of my problem "cocktail"... although none of that seems very disturbing anymore once the glass is on a tripod.
 
Today 17.25 UT.

Zeiss 15x60 old, but completely overhauled by Zeiss.

~12 day moon, very large >33 arcminutes maybe. Perigee tomorrow 09.00UT 33'45", second largest of 2018.
Clear sky, transparent.

Green false colour around limb with moon central in field, but I forgot to place the limb dead centre.
Green and mauve fringes to limb off axis nearer edge.
Moon seemed really large.

Field is curved. Moon is out of focus near field edge, but one can focus and get it sharp again. I have little accommodation.

Contrast may be lowish, but severe light pollution and I didn't compare with say a 15x56.

Some change in shape nearer edges but not drastic.

Earlier, in late sunshine, a white pillar at 120m looked white and had no central false colour but green and mauve near field edges.

I consider this Zeiss 15x60 to be a fine binocular, despite the old design.

There is rarely any sign of atmospheric degradation here at 120m with binoculars, even with a scope at 100x magnification things are usually stable terrestrially. Maybe in mid summer heat the atmosphere gets unsteady.
I do see degradation viewing the Sun with the H alpha scope at 32x as the Sun gets higher than 25 degrees elevation. I usually observe early morning or late afternoon.

The Canon 18x50 IS handheld with the IS on is in a different league to any non stabilised binocular regarding resolution.
I don't use tripods with binoculars. The whole point to me is the freedom to hand hold.
 
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tenex said:
Thanks, I've been trying to figure out why it's been so long since I used this Zeiss. It was mainly #3, and perhaps also some #2 and #4 (in warm winter sun over snow). As soon as I put them on a tripod I got the great view I wanted. Even a monopod helps tremendously. I wasn't sure what was going on because somehow my idea of hand-shake was a sharp image that just jumped around until steadied better. But beneath that really obvious motion there must be a subtler level of unsteadiness, even when I think I'm doing pretty well, that gives an impression of unsharpness. I didn't understand that clearly before.

The problem with this Zeiss is it really begs to be handheld, and seems built for that. I suppose that would work well for any practical purpose, spotting game or whatever, but when I just want to admire the view it's not going to be ideally sharp. I presume the same would be true of any 15x.

Also, I have a simple tripod adapter that may not be the most convenient, as the bino has to be upside-down, requiring reversing the diopter and leaving less room for the nose. Are there better ones?
Click to expand...

I use my Fujinon 16X70, rested on a partly raised car window, and can see a very significant difference over 10X. The view is nowhere as "immersive" or as "brilliant" but I can see quite a bit more.

That said, I prefer to use my Swarovski EL SV, but use the Fujinon when I can't quite see what I want to. If I still can't see it, I look at something else.
 
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Binastro said:
I consider this Zeiss 15x60 to be a fine binocular, despite the old design...
I don't use tripods with binoculars. The whole point to me is the freedom to hand hold.
Click to expand...

I agree completely. Even 10 years ago I felt I could do that, despite a bit of jitter. Somehow I wish I could have found the problem to be in the binocular.
 
I just re-read, in a 1965 book called Binoculars and All Purpose Telescopes, by Dr. Henry Paul, about the subject of "Dirty Optics". He wrote of dust, moisture, mold, etc., eventually penetrating the insides of older binoculars in the era before binoculars were made with waterproofing and "airtight" qualities. Perhaps disassembly and cleaning of all optics would improve the image. But what price glory?
 
fleurviola said:
I just re-read, in a 1965 book called Binoculars and All Purpose Telescopes, by Dr. Henry Paul, about the subject of "Dirty Optics". He wrote of dust, moisture, mold, etc., eventually penetrating the insides of older binoculars in the era before binoculars were made with waterproofing and "airtight" qualities. Perhaps disassembly and cleaning of all optics would improve the image. But what price glory?
Click to expand...

Good Job, Fleurviola:

It is disheartening that it has taken 19 posts to get to the culprit. But, don't think that modern sealing will solve the problem. 'Make things better? Yes. Solve the problem? No. I have worked on many good military binos from the sandbox of the Middle East wherein the sand is on par with being at least as fine as flour and which can "fog" optics in a relatively short time ... and does. :cat:

Bill
 
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