Leica and chromatic aberration (1 Viewer)

Tringa45 · Sep 27, 2018

ronh said:
The Zeiss FL still represents the standard in lateral CA correction, with the possible exception of the Kowa Genesis, which may use actual freakin' fluorite crystal in the objectives!, supporting the general idea of lateral CA coming primarily from air spaced objectives.

Hi Ron,

AFAIK Kowa only use fluorite crystal in their 55 mm and 88 mm scopes. The Genesis binoculars and some of their other scopes use so-called XD glass, probably containing fluorine ions.

I was at Photokina yesterday and Vixen were exhibiting a new 55 mm f5,5 fluorite apochromatic refractor. It's probably primarily intended for use with field flatteners as an astrograph and, IIRC has four elements and is the first Vixen fluorite refractor for decades. I asked the Japanese salesman/engineer if fluorite still offers advantages over FPL-53. He answered in the affirmative - I don't know.

Regards,
John (Russell)

henry link · Sep 27, 2018

John,

I'd be interested to know what the advantages of Fluorite are. I recall Roland Christen of Astro-Physics saying about ten years ago that he could make essentially the same scope, whether the material was Fluorite or FPL-53

I guess you would have mentioned any new Kowa spotting scope at Photokina? Where is that new 100mm TSN Fluorite?

Henry

Tringa45 · Sep 27, 2018

Henry,

Well one theoretical advantage of fluorite is its homogeneity, but if it's only one of fifteen elements that is probably of no consequence. Disadvantages are its vulnerability to moisture, fragility and I believe a relatively high coefficient of thermal expansion.

I didn't ask about new scopes but there was a hint that there might be new 44 mm Genesis bins next year to address some customer issues (big eye cups?).

John

ronh · Sep 28, 2018

Adhoc,
In a situation like that I would certainly have noticed lateral CA in a Leica. Any normal birder should have been irritated, but I would have probably thought "lateral CA, cool".

Tringa45,
Thanks for straightening me out on the Kowa Genesis objectives. I guess crystal would be wasted at 10.5x, but judging from most reviews, Genesis objectives must have some pretty good fluoride glass.

Hi Henry,
Golly, thanks, but if it's up to me the rabbit hole must be full of lost souls by now. I stlll look in most nights though, especially for contributions from you.

Ron

adhoc · Sep 28, 2018

Ron, I am just tripping round the rim of the rabbit hole and that is not cool :-( Maybe I should go back from these woods, relax, and wait for a report someday of a 7x that is sharp, bright, color-neutral, with no aberrations that bother, and no chromatic at all

(And smallish of course I insist.)

John Frink · Sep 28, 2018

adhoc said:
...and wait for a report someday of a 7x that is sharp, bright, color-neutral, with no aberrations that bother, and no chromatic at all (And smallish of course I insist.)

Just my opinion, of course, but I find my 7x42 UV HD+ controls lateral CA about as well as anything out there; and I've tried most of them. It's quite compact, with good ergonomics if you don't mind the thumb ridges, and a smooth focus action; what's not to like?

adhoc · Sep 29, 2018

Thanks John. That is more than, or not really, an individual's opinion there, it is how an individual actually sees the image, via his/her optical-neural system, contra other individuals via theirs! Unfortunately I do see lateral CA in Leica, and I am worried about the two situations one described and one photographed by Quincy88.

Variability among individuals in another matter, visual acuity, has provoked much haranguing by me in this forum for reviewers of binoculars to state or indicate theirs. Indeed I suggest information not only with regard to acuity but other conditions such as astigmatism, degree of cataract, etc. Most people, even most on this forum I would guess, are not aware of their acuity, and some may not be aware of the onset of those other conditions. A longish digression, but acuity and seeing CA might possibly be connected.

Mike F · Sep 29, 2018

adhoc said:
Most people, even most on this forum I would guess, are not aware of their acuity, and some may not be aware of the onset of those other conditions. A longish digression, but acuity and seeing CA might possibly be connected.

adhoc, is it possible that seeing CA is made more likely by some forms of loss of acuity? I don't know - it's just a thought.....

I'm 55 and have very good acuity AFAIK. At least opticians always talk about the fact that I have very good 'correctability' by which they mean that I have almost 20/20 vision which the right prescription. I'm am very slightly short sighted (-1.00) and have a slight astigmatism in both eyes, but otherwise no problems. I have my eyes checked regularly because there is a history of glaucoma in my family.

I can certainly induce CA in my 7x42 UVHD+ but I never see it in normal use. I've always thought that CA was largely a function of poor IPD and focus, but I'm no expert and defer to those who are. However, my only bin for years and years was a 10x25 BCA and I think that because of my experience of using that bin I am good at setting the IPD correctly. After all, if you don't set it right with a bin with an exit pupil of 2.5, you know about it pretty soon!

chill6x6 · Sep 29, 2018

ceasar said:
I almost never see CA in normal use with any of my binoculars and I use an 8x42 Ultravid Blackline often. And I don't look for it. As you know the Ultravid Blacklines still have Leica's original Ultravid coatings.

Bob

Troubador said:
If so then the CA and the level of correction applied to it must be what Leica thinks is the right balance between CA/Compact Length/Cost. Other brands have their own opinions of course. Troubadoris never complains about CA in her Ultravid 8x32 HD.

Lee

dries1 said:
P.S. leica makes a great glass, perhaps it is the vision of the persons who keep harping on CA. If Leica does not work for an individual, go with another brand, there are many today to choose from.

Andy W.

WJC said:
Bless you, Andy; you may someday qualify for curmudgeon first class. :cat: Taking your direction a little further, the whole problem may be solved by adding a few $$$$$$ to the equation. These companies are trying to keep their doors open, and they can't do that by catering to the few but vocal nit-noids

Cheers,

Bill

John Frink said:
Just my opinion, of course, but I find my 7x42 UV HD+ controls lateral CA about as well as anything out there; and I've tried most of them. It's quite compact, with good ergonomics if you don't mind the thumb ridges, and a smooth focus action; what's not to like?

There are some pretty good actual user/owners reports of said binocular model in the above comments. I'd like to add myself to the group. Go out in the field and use the dang binocular. I know of all the binoculars I have the SV 8X32 and UVHD+ 7X42 are probably #1a and #1b...

dries1 · Sep 29, 2018

That is why each person looking to buy a glass is to check it out them selves rather than rely on others opinions, which will vary. As Mike and others have said, checking the IPD is extremely important, and I would add is the fit to the facial ocular structure is important, some glass will not be a fit ergonomically after a sufficient time trial, move to another that will.
Frankly regarding acuity, I do not see CA unless I look for it in some glass, and the thought of superior acuity being able to see CA, well, is IMO hogwash. As Mike suggested, and I will push further, is more likely the other way around.

Andy W.

typo · Sep 29, 2018

dries1 said:
......
Frankly regarding acuity, I do not see CA unless I look for it in some glass, and the thought of superior acuity being able to see CA, well, is IMO hogwash. As Mike suggested, and I will push further, is more likely the other way around.

Andy W.

Andy,

Do you think you could explain those comments? They seem quite contrary my understanding about how the eye works, particularly with regard to longitudinal CA.

David

A2GG · Sep 29, 2018

chill6x6 said:
There are some pretty good actual user/owners reports of said binocular model in the above comments. I'd like to add myself to the group. Go out in the field and use the dang binocular. I know of all the binoculars I have the SV 8X32 and UVHD+ 7X42 are probably #1a and #1b...

My own 2 cents: agree with others who have said they don't notice CA in the Ultravid when out birding because they're not looking for it. Only time I notice CA is when alignment is not right. For example, when bringing the bin up to my eyes quick for a bird in a gray/white sky, if the alignment isn't right, I'll see CA round the bird. But once I correct alignment it's totally gone.

If I actually test for CA , like when I first got my Ulvid, I can see it off center in some conditions and it seems minimal to me. Lower power (7x) may help here to minimize CA compared to the 8-10x models. But ordinarily I don't notice any CA when birding b/c I'm concentrated on the birds and critters about.

IMO I think the ultravid plus 7x controls CA overall pretty well. It hasn't been any issue for me.

I also wonder how much my polycarbonate eyeglass lenses are contributing to any perceived CA. When I first got my eyeglasses I noticed CA in them, but now I don't anymore from becoming so used to them.

Alexis Powell · Sep 29, 2018

I think that seeing CA, like many aspects of visual perception, is dependent upon visual awareness, not acuity. As a long time photographer (esp. in the color slide film days), I know that my awareness of the color temperature of light, relative brightness of shadows versus highlights, effects of perspective on apparent shape, and many other factors (including aberrations induced by my optical tools, such as CA) grew tremendously in the first few years that I began taking photographs with attention to the process and its outcomes versus what I was experiencing visually when I took them. Much of becoming a successful photographer was learning to see more like the camera and film. People who are not photographers or representational artists can live their whole lives without seeing/perceiving these and many other things.

I find it very easy to find CA in most binoculars when I look for it. I also find it easy to relax, use the bins, and tune it out or remain unaware of it when I want to. But if one is buying a bin for critical observation, and frequently using it at the limits of one's acuity, I think it would be folly to buy a bin with a lot of CA, even if one could not see it (in that bin, or other bins) because the destructive effects of CA on the image are there, whether one is aware of its presence or not. It will reduce the color information and clarity of the image.

--AP

Binastro · Sep 29, 2018

I agree with Alexis's comments in post 33.

I also see CA in many binoculars if I look for it.
The 12x50 Ultravid that I just used certainly has it, looking at the moon.

But I was brought up on refracting telescopes and just ignored false colour.
My slightly younger astronomer friends hate refractors because they were brought up using Newtonians, and notice every bit of false colour.

I asked Horace Dall why I saw some colour images with strong colour differences in strong 3D.
He replied immediately that ones eyes have chromatic aberration.

In addition, I suppose that people wearing glasses using binoculars add some additional colour errors.

I also see lots of CA in short focus refractors.

My optics lecturer friend also told me that Newtonians do have a little false colour but I cannot remember the reasoning. Maybe several orders of aberrations?

In the early hours I was looking at a fox about 15 metres away that was around for a long time licking leaves and the pavement. It seemed to have trouble finding proper food. The fierce summer must have affected them with no rain for two months.
Usually they move away quickly. One managed to extract food from an overflowing secure street bin.
In the 8x32 Leica BA I could see colour in its fur even in street lighting.

A2GG · Sep 29, 2018

Even though I'm partial to the Ultravid and Leica in general, I wouldn't recommend Leica bins to someone sensitive to CA. This is the main flaw people seem to bring up about Leica binos. I would suggest Zeiss FL instead or Kowa Genesis based on high regard here for its CA control just like the FL (never tried a Genesis myself though).

Same thing with other problems like glare; I wouldn't recommend Swaro SV 8x32 since I saw it for myself.
Personally, I'd be super happy with an SV 8x32 despite its one and seemingly only flaw; I don't think I would care that much about it since it has just too much going for it overall. There's no perfect binocular out there. This has been said a ton of times here, but it's true and if looking for something perfect it will be a never ending search. I did this with handbags in the past and never found that perfect one, but stupidly spent too much money and time. I did the same albeit to lesser degree with binoculars.

dries1 · Sep 29, 2018

David, If I do not see longitudinal CA in a Leica glass, does it mean that I have low acuity?

Andy W.

typo · Sep 30, 2018

Andy,

Not necessarily, as Alexis points out, but without excellent VA you are quite unlikely to see it. I think Adhoc asks a perfectly reasonable question.

David

dries1 · Sep 30, 2018

So in a sense you are saying that observing CA is a learned process, to (achieve)/obtain visual awareness (VA), through as Alexis points out, experience with photography.

Andy W.

typo · Sep 30, 2018

Andy,

You need to step back a bit. Your eye is naturally riddled with CA, but, keeping it simple. you have learned not to see it. The brain remaps your visual information and fills in the gaps to create what you think you see, and to a significant extent, what you expect to see. How accurately it is able to will depend to some extent of the visual training you have; artist, photographer and so on. The accuracy of the correction also very much depends on the quality of the detail it receives, or visual acuity.

Just to confuse the matter further, the brain only selectively processes the available information. It uses low resolution sampling for high speed information acquisition and high resolution for slower, detailed analysis. When and where in your visual field this high and low resolution processing is applied will depend on the type of information you decide you need from the view. I'm sure that includes the presence or absence of abnormal levels of peripheral CA for example.

I'm sure for some I've oversimplified the explaination, but I hope I've explained enough for you to grasp some of the diverse reasons why there are bound to be difference in opinion about the level of CA between different users, but I hope you understand why it is quite absurd to suggest acuity is not a factor.

I repeat, I think Adhoc asked perfectly justifiable question, and I'm pleased Mike F had the grace to answer it. I hope more will follow his example.

David

paddy7 · Sep 30, 2018

When i first saw CA in binoculars, i had no idea what it was, therefore assume i wasn't 'looking for it.' I looked it up on the internet - purple/green fringing particularly.
Having been the first aberration i actually had a name for, it became the thing i subsequently looked for, or noticed almost immediately, resulting in a particularly negative response to that particular unit.
I have subsequently realised that some degree of CA can be induced in almost any optics, by really pushing the boundaries. For instance, looking at a line of distant, dark trees (at least 1km away) on a bright day at the edge of vision.
I've also found that it is more obvious in what i would call 'grey and bright' - those days of cloud cover, but reasonably high light levels.
My experience with Leica, unfortunately (as i love so much about the approach to binoculars in all other respects) has been that CA has been too obvious.
However, at Bird Fair this year, i tried the 7x42 UVHD+ and thought this was the best performer of the range in terms of control of CA. Whether this is a feature of the reduced magnification, i don't know. It instantly became my favourite Leica model.
With regard to eye position, if one has the luxury (with larger EPs or oculars) of flexibility, it seems to be possible to reduce CA, so there is some user responsibility involved before dismissing a set of bins as unacceptable, and it is apparent that users vary in their perception/acceptance of CA.
I ended up with the FL 8x32, which i still consider the champ of CA suppression.
In terms of acuity, i have measured myself at 20/15, wear glasses for reading but nothing else, and have a mild astigmatism. My eyesight is not exceptional in either direction, but there are various aberrations within optical chains i can tolerate more than i can stand obvious and easily-induced CA, for whatever reason it occurs.

Leica and chromatic aberration (1 Viewer)

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