Comparing Zeiss and Swarovski 32 /30 models (1 Viewer)

denco@comcast.n · Apr 23, 2019

From Scopeviews review on the Zeiss 8x32 FL.
http://scopeviews.co.uk/Zeiss8x32FL.htm
"Flat field?
Like most Zeiss binoculars (the new SFs excepted), the field drops off at the edge more than in binos with field flatteners. The field is so wide that this isn’t a huge problem during the day and it does make for more comfortable panning."

http://scopeviews.co.uk/Zeiss7x42FL.htm
"Flat field?
The field has a large perfect sweet spot, but the field does curve off a lot at the very edge, where it is only good for context. This typical of most Zeiss binoculars"

https://www.allbinos.com/191-binoculars_review-Carl_Zeiss_Victory_8x32_T*_FL.html
"Astigmatism Very slight. 8.8/10.0"

I have never heard of the Zeiss 8x32 FL's or 7x42 FL's having a flat field. How could they if they don't have a field flattener. According to Allbino's they do not have very much astimatism either. I have always thought their softer edges was due to field curvature. That is new one on me if it is true.

Alexis Powell · Apr 23, 2019

[email protected] said:
From Scopeviews review on the Zeiss 8x32 FL.
http://scopeviews.co.uk/Zeiss8x32FL.htm
"Flat field?
Like most Zeiss binoculars (the new SFs excepted), the field drops off at the edge more than in binos with field flatteners. The field is so wide that this isn’t a huge problem during the day and it does make for more comfortable panning."

http://scopeviews.co.uk/Zeiss7x42FL.htm
"Flat field?
The field has a large perfect sweet spot, but the field does curve off a lot at the very edge, where it is only good for context. This typical of most Zeiss binoculars"

https://www.allbinos.com/191-binoculars_review-Carl_Zeiss_Victory_8x32_T*_FL.html
"Astigmatism Very slight. 8.8/10.0"

I have never heard of the Zeiss 8x32 FL's or 7x42 FL's having a flat field. How could they if they don't have a field flattener. According to Allbino's they do not have very much astimatism either. I have always thought their softer edges was due to field curvature. That is new one on me if it is true.

Not sure what you are doing here Dennis. If you are asking for an explanation for the above quoted statements, I'd say that in the case of statement #1 that the reason for the "field dropping off" is that the FL suffers from astigmatism towards the edges, that statement #2 is an incorrect attribution of the resolution fall off to field curvature rather than astigmatism, and that statement #3 is either incorrect, is correct in the grand scheme of things (compared to all bins) but not in comparison to a bin that is well corrected for astigmatism, or is somehow a measure of astigmatism averaged across the view or only near the center of the view rather than a measure from the outer portion of the FOV.

How can a bin have a flat field without having a field flattener? By building such performance into the combined result of the interactions of the other lens elements. You don't have to trust me about the degree of curvature versus astigmatism in the 8x32 FL. Obtain a unit, focus the center on something with both horizontal and vertical detail, view that same something off-axis, and see if you can touch up the focus to make it look better overall. You'll find that you can't, and that instead, only the resolution of vertical or horizontal lines improves (but not together).

--AP

denco@comcast.n · Apr 23, 2019

John. How many lenses per side do the Zeiss SF's have? If they have more than the FL that for sure would be an indicator of field flatteners.

denco@comcast.n · Apr 23, 2019

Alexis. It is just the first time I have ever heard of the Zeiss 8x32 FL having a flat field. When I had my Zeiss 8x32 FL I remember distinct field curvature and soft edges and low astigmatism. All the FL's I owned were pretty much the same in that respect. Have you ever star tested your 8x32 FL for astigmatism? That would be a good way to see if it had it. The concentric rings would be oval. I star tested my FL's when I had them and they did not show a lot of astigmatism.

Alexis Powell · Apr 23, 2019

[email protected] said:
...I remember distinct field curvature...

You either misunderstood what you saw or you are not remembering accurately.

--AP

denco@comcast.n · Apr 24, 2019

Alexis Powell said:
You either misunderstood what you saw or you are not remembering accurately.

--AP

" The 8x32 has plenty of off-axis astigmatism but it also has a _very_ flat field." I never found the Zeiss FL to have plenty of off-axis astigmatism and I remember it well and I know what astigmatism is. Albino's never observed it either so I guess they agree with me. I think you should star test your FL. It could very well be a bad sample. Maybe you are confusing astigmatism with distortion. From Allbino's reviews.

Zeiss 8x32 FL
Astigmatism Very slight. 8.8/10.0

Zeiss 8x42 FL
Astigmatism Very low. Almost point-like images of stars. 8.8/10.0
Distortion The distance of the first curved line from the field centre compared to the field of vision radius: 34% +\- 5% 3/10.0

henry link · Apr 24, 2019

Figure (c) below from page 168 of "Telescope Optics" by Rutten &van Venrooij shows the kind of high astigmatism, combined with low field curvature that Alexis is talking about.

The authors describe it this way: "the tangential and sagittal focal surfaces are symmetrically placed with respect to a plane perpendicular to the optical axis, thus avoiding field curvature altogether."

In the FLs the problem is that there is a wide spread between the tangential and sagittal foci at the field edge, so even though the midpoint between them falls close to the plane of the center focus the image at the field edge can only be focused on either the tangential or sagittal focus, not both simultaneously. In other words there is high astigmatism at the edge.

Allbinos tests for axial astigmatism only, not off-axis astigmatism.

The SF has 10 lenses per side, 7 in the eyepiece, 3 in the objective. The field flattener is a singlet.

Alexis Powell · Apr 24, 2019

[email protected] said:
...I never found the Zeiss FL to have plenty of off-axis astigmatism and I remember it well and I know what astigmatism is. Albino's never observed it either so I guess they agree with me. I think you should star test your FL. It could very well be a bad sample...

I really think that you need to take another look through the FL. Although I fancy myself a philosopher of sorts, who wouldn't normally say such things, I think that there is an objective truth to adjudicate this disagreement, and since I own the Zeiss 8x32 FL and have used it almost weekly for about 15 years, I'm quite sure that I closer to that truth than is your memory. I "star tested" my unit many years ago, and I've tried at least a dozen 8x32 FL of various vintages over the years and I've not found them to differ in this respect. You will also find plenty of others who note the astigmatism in the FL in various BirdForum threads.

[email protected] said:
Maybe you are confusing astigmatism with distortion.

Uhhh...and maybe I'm not. But hold on, maybe you're on to a bold and provocative new hypothesis. Does the Zeiss 8x32 FL have a lot of distortion? I've never heard anyone say that, nor have I noticed it myself. Have you? I guess you must have or I suppose you wouldn't have suggested it.

Hold on, let me check........Nope, it seems like astigmatism and not distortion. But why trust my own eyes? The authoritative AllBinos website (maybe you've heard of it) says of the 8x32 "Even the distortion, which was a major complaint in the 10x42 model (and that set still managed to win our big test of binoculars of that segment, mind you) was corrected well here and is no longer a problem." It seems your explanation is contradictory to what AllBinos found.

[email protected] said:
From Allbino's reviews.

Zeiss 8x32 FL
Astigmatism Very slight. 8.8/10.0

Zeiss 8x42 FL
Astigmatism Very low. Almost point-like images of stars. 8.8/10.0
Distortion The distance of the first curved line from the field centre compared to the field of vision radius: 34% +\- 5% 3/10.0

Yes, I saw this and I already responded to it (in a previous post). To reiterate, either the AllBinos measurement is incorrect, is correct in the grand scheme of things (compared to all bins) but not in comparison to a bin that is well corrected for astigmatism, or their measure is a measure of astigmatism averaged across the view or (most likely, I think) from near the center of the view rather than being a measure of the outer portion of the FOV.

--AP

Alexis Powell · Apr 24, 2019

henry link said:
...Allbinos tests for axial astigmatism only, not off-axis astigmatism...

Bingo!

Thanks, Henry, for this and for the rest of your post (sent while I was still writing my reply to Dennis).

--AP

denco@comcast.n · Apr 24, 2019

Still a lot more distortion on the Zeiss 8x32 FL versus a flat field binocular like the Nikon 8x32 EDG. I have had them both and I can substantiate that. The FL's I have had had soft edges compared to flat field binoculars like the EDG or SV. If it caused by off-axis astigmatism that is news to me. It could be other things also. There is no objective proof that it is. IMO astigmatism whether off-axis or not is not something to be desired in an optical system.

Zeiss 8x32 FL
Distortion The distance of the first curved line from the field center compared to the field of vision radius: 56% +/- 5% 6/10.0

Nikon 8x32 EDG
Distortion The distance between the first curved line and the field center compared to the field of view radius: 86% +\- 5% 10/10.0

Off-axis astigmatism must not be seen with a star test because the FL's I have star tested have been quite good. I usually star test most binoculars I have just to see if they are good performers or not. The only way you could tell if a binocular has off-axis astigmatism would be if you could not focus the edge or else I would think it would probably be field curvature. How do you know it is not Coma or even your own eyes causing the astigmatism? Isn't everybody eyes astigmatic to some extent? I just don't see how you can prove it is off-axis astigmatism. It is interesting that the Zeiss SF has less lenses per side than the 10x32 FL maybe that is an indicator that the 10x32 FL does have some sort of field flattener.

A2GG · Apr 24, 2019

Dennis (post 50),

I believe it's the 10x32 FL that's alleged to have the field flatteners and not the 8x32.
That's what Lee mentioned he heard and he is trying to get a final answer on this through
his contacts.

Alexis Powell · Apr 24, 2019

[email protected] said:
Still a lot more distortion on the Zeiss 8x32 FL versus a flat field binocular like the Nikon 8x32 EDG. I have had them both and I can substantiate that. The FL's I have had had soft edges compared to flat field binoculars like the EDG or SV. If it caused by off-axis astigmatism that is news to me. It could be other things also. There is no objective proof that it is. IMO astigmatism whether off-axis or not is not something to be desired in an optical system.

Zeiss 8x32 FL
Distortion The distance of the first curved line from the field center compared to the field of vision radius: 56% +/- 5% 6/10.0

Nikon 8x32 EDG
Distortion The distance between the first curved line and the field center compared to the field of view radius: 86% +\- 5% 10/10.0

Off-axis astigmatism must not be seen with a star test because the FL's I have star tested have been quite good. I usually star test most binoculars I have just to see if they are good performers or not. The only way you could tell if a binocular has off-axis astigmatism would be if you could not focus the edge or else I would think it would probably be field curvature. How do you know it is not Coma or even your own eyes causing the astigmatism? Isn't everybody eyes astigmatic to some extent? I just don't see how you can prove it is off-axis astigmatism. It is interesting that the Zeiss SF has less lenses per side than the 10x32 FL maybe that is an indicator that the 10x32 FL does have some sort of field flattener.

Wow Dennis, since you clearly trust no one but yourself (and maybe AllBinos, sometimes), I'll say again, you owe it to yourself to assess the 8x32 FL again yourself. Keep us posted on your findings if you do that.

FYI, flat field has little to do with distortion. Some flat field bins, like the Swarovski 8.5x42 EL SV (which has a flat field as well as very little off-axis astigmatism) have quite a bit of distortion.

--AP

denco@comcast.n · Apr 24, 2019

Gilmore Girl said:
Dennis (post 50),

I believe it's the 10x32 FL that's alleged to have the field flatteners and not the 8x32.
That's what Lee mentioned he heard and he is trying to get a final answer on this through
his contacts.

Thanks, for that. I mentioned the 10x32 FL as possibly having field flatteners at the bottom. Up above I was talking about distortion in the 8x32 FL.

denco@comcast.n · Apr 24, 2019

Alexis Powell said:
Wow Dennis, since you clearly trust no one but yourself (and maybe AllBinos, sometimes), I'll say again, you owe it to yourself to assess the 8x32 FL again yourself. Keep us posted on your findings if you do that.

FYI, flat field has little to do with distortion. Some flat field bins, like the Swarovski 8.5x42 EL SV (which has a flat field as well as very little off-axis astigmatism) have quite a bit of distortion.

--AP

I trust you Alexis I just don't agree with you all the time which is ok.

I feel the Swarovski 8.5x42 SV is one of the most distortion free binoculars I have used and Allbino's says so also giving it a perfect 10 on distortion. I think we have a fundamental difference in our definition of distortion. But I will try the Zeiss FL again if I get the chance. I am especially interested in trying the Zeiss 10x32 FL to see if it does have a flat field as some say. There was a thread on it over at Cloudy Nights and they were saying the 10x32 FL is a hidden secret because it does have low distortion and a flat field so maybe Lee is correct. I once compared the Swarovski 8x32 SV, Nikon EDG 8x32 and the Zeiss 8x32 FL and I liked the SV best, EDG 2nd and FL 3rd because I like sharp edges and I preferred the ergonomics of the SV because it is smaller and slimmer than the other two. On-axis the FL is an excellent binocular but it does have softer edges. It would be nice if Zeiss would make an 8x32 SF. That would be an interesting binocular with most likely a huge FOV and sharp edges. That is what I LIKE!!

Swarovski 8.5x42 SV
Distortion The distance of the first curved line from the field center compared to the field of view radius: 91% +\- 3% 10/10.0

https://www.allbinos.com/251-binoculars_review-Swarovski_EL_8.5x42_Swarovision.html

henry link · Apr 24, 2019

Dennis,

Everything about the astigmatism in the FLs was beat to death long ago. Try wading through this old thread:

https://www.birdforum.net/showthread.php?t=184977&highlight=astigmatism+sagittal

If you want examples of objective techniques for distinguishing between astigmatism and field curvature go to my posts #52 and #59 on page 3.

As for distortion, Allbinos apparently recognizes only one kind, pincushion. They seem to be unaware that as pincushion distortion decreases angular magnification distortion increases and that's the stuff that causes "rolling ball". There is no such thing as a distortion free binocular.

denco@comcast.n · Apr 25, 2019

henry link said:
Dennis,

Everything about the astigmatism in the FLs was beat to death long ago. Try wading through this old thread:

https://www.birdforum.net/showthread.php?t=184977&highlight=astigmatism+sagittal

If you want examples of objective techniques for distinguishing between astigmatism and field curvature go to my posts #52 and #59 on page 3.

As for distortion, Allbinos apparently recognizes only one kind, pincushion. They seem to be unaware that as pincushion distortion decreases angular magnification distortion increases and that's the stuff that causes "rolling ball". There is no such thing as a distortion free binocular.

Thanks, for the thread link but I already read through it. It seems there are always trade offs in optics. Actually, pincushion distortion is the one I care most about since I am not bothered by rolling ball. Allbino's probably consider pincushion to be the most important distortion for most people but there are a lot of people that are bothered by AMD and it's effects. You can't improve one thing without something else getting worse it seems in optics. I don't care for astigmatism or field curvature in my binoculars. I guess that is why I prefer Swarovski SV's in general.

Swissboy · Apr 27, 2019

Finally - after more than two months - got my 8x42 FL back from Zeiss. It looks and feels like new. So I guess those 380 Swiss Francs I need to pay are OK. Still have the 8x32 FL on loan from Zeiss, and it's clearly the 42 model that wins on all aspects except for weight.

Troubador · Apr 29, 2019

[email protected] said:
It is interesting that the Zeiss SF has less lenses per side than the 10x32 FL maybe that is an indicator that the 10x32 FL does have some sort of field flattener.

Dennis

SF has exactly the same number of lenses as FL10x32 i.e. 11. See drg below. Don't forget the field flattener has two lenses.

The evidence for a 'field flattener' fitted to FL 10x32 is overwhelming (see below) but note that Henry's idea that it was fitted primarily to boost magnification from 8x to 10x is almost certainly correct as 32s traditionally sell fewer than 42s and doing this would have allowed the two FL 32s to share the same eyepiece and so keep costs down.

The evidence for a field flattener in FL 10x32 is as follows:

1. A senior sports optics executive has said there is one.

2. https://shop.zeiss.co.uk/ZEISS-Victo...d4047006323104 Scroll down and look on the left for the pic of a Pied Kingfisher and title Newly Developed Ultra-FL Lens and it states clearly here that a field flattener is fitted.

3. https://www.zeiss.com/sports-optics.../competences/lens-concepts.html#lens-concepts Go to the final paragraph about multiple lenses and here it states FL 10x32 has 11 lenses in each optical tube. The sectional drawing published years ago by Zeiss of FL 8x32 and posted elsewhere on this thead shows clearly that the 8x32 has only 9 lenses. The extra 2 lenses of 10x32 will be the Smyth-Barlow doublet commonly used as, and referred to as, a field flattener.

4. The weights on the website for these models show 10x32 is 10grams heavier than 8x32.

Lee

dries1 · Apr 29, 2019

Sorry, but all this back and forth over a 10X32 made years ago?

Andy W.

denco@comcast.n · Apr 29, 2019

Lee. I believe the evidence does definitely indicate a field flattener in the 10x32 FL. There was a post over on Cloudy Night's where the member said the 10x32 FL was a hidden secret because it was sharp to the edge and a great binocular. I think it is like you say you have to go up a little higher in the Zeiss ranks to get a correct answer. I will have to try a Zeiss 10x32 FL sometime. I am getting into 10x32's lately. I have always avoided them because the popular opinion is they are fussy and not that great frankly. Will let me tell you that opinion is incorrect if you are dealing with alpha's. I have the Swarovski 10x32 SV and the Nikon 10x32 EDG and they are both excellent 10x's and not fussy at all and the handling and size and weight is so much nicer than a 42mm. Trouble with the Zeiss 10x32 FL is you never see one discounted. Kind of like a Swarovski. Even though the FL was introduced years ago it is still a top alpha binocular and probably will be unless Zeiss makes an SF in a 32mm. The FL is still Zeiss's best 32mm binocular. I consider the FL in the top three 32mm's along with the SV and the EDG.

Comparing Zeiss and Swarovski 32 /30 models (1 Viewer)

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