I think Zeiss prioritized size and weight over the optics in the SFL 8x50. I thought the SFL 8x50 was very short for a 50mm when you look at other large aperture binoculars like the FL 8x56 and how long they are. They are long so they have a slower F-Ratio, which helps with the CA.
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SFL 50mm Second Look - does first impressions really last? (2 Viewers)
- Thread starter HenRun
- Start date
Big aperture lower magnification binoculars generally have a smaller FOV and you are right 58 degrees is decent, but the problem lies in the shortness of the binocular which creates more CA.
Why less F O V with larger aperture?
How come that a Xx30 bino of the same line (almost always, what I've seen) have larger F O V than a Xx40, or even more than a Xx50? It can't just be to compensate for less light gathering, can it? ;) (I mean, that's what the lesser weight does!) :-O
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temmie
Well-known member
I know when I look through bins with more CA in the center, birds don't look as sharp and crispy. But if we're talking about e.g. CA on the outer edges that you have to speficially look for off-center, it would maybe not be as big of a dealbreaker (for me).
Big aperture lower magnification binoculars generally have a smaller FOV and 58 degrees is decent, but the problem lies in the shortness of the binocular.
So after 10 pages we know the 50mm SFL have more CA than the 40mm, and the 50mm UVHD 
Good to know. I'm allergic to CA as well. Especially at this price point.....and considering my $90 80's Nikon 10x50 porros don't have it. Probably less of an issue for hunting and astronomy. For hunting the 50mm SFL is 6 or 7 ounces lighter than the 54mm HT? And lower cost.
I actually have three pairs of Nikon 50mm porros, 7x50SP, 10x50 Gold Sentinel, and 12x50 SE, and none of them have any CA in the middle. The 12x50 SE is the same weight as the SFL. No chemicals sprayed on the lenses either. The 7x50SP is missing a focuser though.....could be a problem for birding
Good to know. I'm allergic to CA as well. Especially at this price point.....and considering my $90 80's Nikon 10x50 porros don't have it. Probably less of an issue for hunting and astronomy. For hunting the 50mm SFL is 6 or 7 ounces lighter than the 54mm HT? And lower cost.I actually have three pairs of Nikon 50mm porros, 7x50SP, 10x50 Gold Sentinel, and 12x50 SE, and none of them have any CA in the middle. The 12x50 SE is the same weight as the SFL. No chemicals sprayed on the lenses either. The 7x50SP is missing a focuser though.....could be a problem for birding
Yarkho
Optics afficionado
Thanks again HenRun for providing us with wit and information.
From experience I would venture to guess that the violet-green CA has a way of disappearing when observing vegetated areas. So the SFLs 50 will likely make many a hunter happy. Us optical enthusiasts, not so much.. I too am generally unwilling to pay €2k and see violet fringing.
From experience I would venture to guess that the violet-green CA has a way of disappearing when observing vegetated areas. So the SFLs 50 will likely make many a hunter happy. Us optical enthusiasts, not so much.. I too am generally unwilling to pay €2k and see violet fringing.
I usually never consider CA as a problem with binoculars at normal handholdable magnifications. Maybe I am insensitive to that.
But I am still pretty demanding when it comes to spottingscopes and telescopes. Here we are talking about much higher magnifications, though.
But I am still pretty demanding when it comes to spottingscopes and telescopes. Here we are talking about much higher magnifications, though.
Ignatius
Inactive member
This lengthy discussion about CA begs one question as far as I am concerned: if it is true, that some a very susceptible to it, and others almost immune, what are the actual optics/physics involved? I am not talking about the varying focal legths of a lens depending on the wavelength of the light, but about why some eyes/brains perceive that easily while others are kind of blind to it.
It doesn’t “disappear” ……. you just don’t see it, due to loss of contrast, but the light is still smeared out and makes the image mushy.
CA is more than a nuisance. It, like all aberrations, degrades the image. Whether it is enough to see, depends greatly on the viewer.
henry link
Well-known member
How did you do this figuring? Looking at the Zeiss specifications it appears that you simply divided the physical length of the binoculars by their apertures. Did you really think that would work?
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Isthatascratch?
Well-known member
So after 10 pages we know the 50mm SFL have more CA than the 40mm, and the 50mm UVHD
I actually have three pairs of Nikon 50mm porros, 7x50SP, 10x50 Gold Sentinel, and 12x50 SE, and none of them have any CA in the middle. The 12x50 SE is the same weight as the SFL. No chemicals sprayed on the lenses either. The 7x50SP is missing a focuser though.....could be a problem for birding
I don’t know…I have the tropical and (as you know) the depth of field is good like the SP so just focus on the trees etc and bosh ..lovely clear image!
Yarkho
Optics afficionado
The eye lens yellows over time due to UV exposure and people lose sensitivity to violet. On top of it there are differences in individual color vision. My color vision is perfect (tested) and having worn glasses since I was 5 yr old, i can still (barely) see the Sun in Ca II K 396.8nm filter.
I once visually tested a 94mm f/5.5 triplet "apochromat" that an older reviewer described as CA-free. Yet I was shocked to see Montes Apeninnus on the Moon bathed in a sea of violet. And I will say on record that I do saw some CA in Meostar B1+ 10x42 HD. Not to mention the various NL Pures. (But in both it is very very low in the centre, and I have to consciously search for it).
Maljunulo, I know about the "disappearing" in vegetation - there is very little high-contrast areas, not to mention whites, so violet is almost never present and green just gets lost in the surrounding green. Hunters will have no problems with CA.
I once visually tested a 94mm f/5.5 triplet "apochromat" that an older reviewer described as CA-free. Yet I was shocked to see Montes Apeninnus on the Moon bathed in a sea of violet. And I will say on record that I do saw some CA in Meostar B1+ 10x42 HD. Not to mention the various NL Pures. (But in both it is very very low in the centre, and I have to consciously search for it).
Maljunulo, I know about the "disappearing" in vegetation - there is very little high-contrast areas, not to mention whites, so violet is almost never present and green just gets lost in the surrounding green. Hunters will have no problems with CA.
tenex
reality-based
There will be so many more mundane factors involved, like an individual's typical circumstances and use, how much attention they pay to the outer field where CA is worse, and so on. I suspect that in a controlled test you'd find that the vast majority can see it, though in practice they're not bothered much.
I was going to ask how you could have "figured" this without obtaining the actual focal lengths of the optical components from Zeiss, but Henry already solved the puzzle. A new standard in worthless posting, which is really saying something here.
It has been explained many times: the moderators consider the ignore feature an adequate solution, and seem to feel that anyone who doesn't just use it is causing unnecessary trouble themselves.
The unfortunate exception is that when the individual starts a thread, you will see no evidence of its existence, and will therefore miss any worthwhile post that somehow happens to be made in it. I have my own alternate method using browser css that I'll share if anyone wants to PM me.
NDhunter
Experienced observer
Hunters also see and know what CA is, and it may be a surprise to many is that hunters spend
more on high end optics that most birders do. Large objective binoculars such as 50 and 56 are mainly a hunting size, "think low light". CA is found in most all binoculars when pushing for it
on high contrast areas, especially near the edges. This is not news.
For most users it is mostly not very important, but when you look for it, you will see it.
I have nothing to add about the new Zeiss 50, but it is nice to have choices. And I like
to see Zeiss in the game, bringing new products to the marketplace.
Jerry
Ignatius
Inactive member
Yup. And exactly that is what I was asking after - what is it that makes some more prone to CA than others, specifically since CA is decidedly a physical phenomenon that can be explained and defined exactly. Or does this fall into the realm of neuroscience or cognitive science? Which would presumably put it way beyond this forum.
Ok. I'll get my coat.
Certainly part of it.
I asked Zeiss to send me the Focal Length's of all the SFL's and using those specifications will probably be a little more accurate than this equation. The Zeiss SFL 8x50 with a Focal Ratio of 3.2 has quite fast optics and probably for that reason will be more prone to aberrations like CA, although it would probably be bright.
Unit Focal Length = Eye Relief x Magnification
Focal Ratio = Unit Focal Length / Aperture
So the SFL 8x50 binocular with a 20 mm eye relief would have a focal length of 160 mm and a Focal Ratio of 3.2.
"Good Morning Dennis,
This is a great resource for that information: https://skyandtelescope.org/observing/stargazers-corner/simple-formulas-for-the-telescope-owner/
To summarize:
Unit Focal Length = Eye Relief x Magnification
Focal Ratio = Unit Focal Length / Aperture
So a 10x42 binocular with a 18mm eye relief would have a focal length of 180 mm and a Focal Ratio of 4.285
Best Regards,
David Eickelmann
Customer Service
Swarovski Optik North America Ltd.
2 Slater Road
Cranston, Rhode Island 02920
United States
Tel. +1 800 426 3089
[email protected]
SWAROVSKIOPTIK.COM"
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I've been surprised by how well the IF focusing works. No, you can't turn the CF knob on the fly, but the graduated scale on the IF"s enables you to preset the focus quickly for a given situation, and the DOF is large enough for it to work well most of the time.
i.e., for astronomy infinity the 7x50's IF's are set to -.8 for me. For most terrestrial situations, I can turn them to "0" and most things are in focus. If you're observing things closer-up, you can turn them to +1 and go with that. So they can be quite useful for many birding situations. Focusing is more like setting the temperature on an oven. You pre-heat for whatever meal you're cooking
Please stay on topic, which is the SFL 50mm. Members and outsiders that come to read these threads don't want to have to filter through a bunch of unrelated posts. Thanks!I've been surprised by how well the IF focusing works. No, you can't turn the CF knob on the fly, but the graduated scale on the IF"s enables you to preset the focus quickly for a given situation, and the DOF is large enough for it to work well most of the time.
i.e., for astronomy infinity the 7x50's IF's are set to -.8 for me. For most terrestrial situations, I can turn them to "0" and most things are in focus. If you're observing things closer-up, you can turn them to +1 and go with that. So they can be quite useful for many birding situations. Focusing is more like setting the temperature on an oven. You pre-heat for whatever meal you're cooking
