SFL 8x30 worth it? (1 Viewer)

[dries1]

Sometimes if ones eyes are allowed to approach close the exit pupil one can perceive a larger window. Perhaps on the FL your anatomy does not allow you to do the same. I believe the SFL has more generous eye relief.

 

[MiddleRiver]

Sometimes if ones eyes are allowed to approach close the exit pupil one can perceive a larger window. Perhaps on the FL your anatomy does not allow you to do the same. I believe the SFL has more generous eye relief.

Both eyepcs are limited to where they are in contact with eyeglasses. And in both cases I'm seeing the full field-stop.
I realize it's not like a projected image, but I'm having trouble visualizing why a larger eyepiece seems to correlate with a more expansive/immersive view. Words matter and maybe I'm using the terms incorrectly.

 

[dries1]

Sorry did not know you wear glasses. Immersive is one thing, colors contrast etc. however expansive was not something I noticed with the 8x30. Colorful, but not expansive.

 

[MiddleRiver]

Sorry did not know you wear glasses. Immersive is one thing, colors contrast etc. however expansive was not something I noticed with the 8x30. Colorful, but not expansive.

Relative terms: more expansive than the FL's.

 

[dries1]

In other words I did not think the view of the SFL showed me a bigger window than the FL.

 

[tenex]

But the SFL feels like I'm looking through a larger porthole or at least my eye is closer to the 'display', even tho the image portrayed is the same.

I just don't know what the effect is that you're trying to describe here, whatever the language. But if you wear eyeglasses, of course some eyepiece designs may work better with them than others.

 

[Swedpat]

My post never mentions SF or NL. I compared FL and SFL.

FOV for 8x32FL and 8x30SFL is 140m/1000 and 139.4/1000 respectively, according to B&H specs.
Wearing glasses, I can see the field stops on both and I can confirm that the FOV (real world, counting fenceposts or bricks or whatever) is virtually the same.
The SFL has a distinctly larger diameter hunk of glass at eye-piece. 24mm vs 19mm diameter (rounding to the nearest mm).
My math says the SFL ocular area is 60% larger.

I'm not sure how to explain the optics. But the SFL feels like I'm looking through a larger porthole or at least my eye is closer to the 'display', even tho the image portrayed is the same. Or at least that's the way I perceive it. Are you saying that if I'm seeing the full view (field stop just on edge of 'hard'), the view formed on my retina is still diff?

Since this 'effect' is something I note comparing bins and in fact it's often not correlated to FOV, then please explain it to me. Because I'm genuinely interested.

There is a strong relation between eye lens size and eye relief. 24mm lens for SFL is awesome.
And I wonder if you are describing the same as I use to say "open window".
Even if you see the edges of the field it's not instantly sufficient. You need to come 1-2mm closer in order to get the field evenly illuminated, or how to say. Otherwise there is a partial "shadowing" of the image.
Are we talking about the same thing?

 

[Ignatius]

There is a strong relation between eye lens size and eye relief. 24mm lens for SFL is awesome.
...

Is that something that could be expressed as a constant? I might try to get a some figures together to test that with the few binos I own.

 

[Swedpat]

Is that something that could be expressed as a constant? I might try to get a some figures together to test that with the few binos I own.

I am not sure exactly. And it may differ between different ocular designs. But in general wider FOV requires bigger lens to obtain a given ER.
And in general at a given AFOV a bigger lens provides longer ER.

 

[Ignatius]

In the few binos I own I found that relationship to be between 0.7 and 1.0 when one divides ER by ocular dia. However 0.9 and 1.0 are outliers while 0.8 has a frequency of 3 and 0.7 of 4. So this is probably worth nothing.

 

[Patudo]

I get the sense that high end binos have evolved to have larger diameter eyepieces - regardless of ER or FOV - which makes the size of the 'tv screen' larger in front of your eyeball. That makes it seem - even when comparing two binos with equal FOV - more immersive and less tunnel like. The SFL's belong to this trend (if not by a large margin), and specially the 8x40's seem much 'bigger' when I bring them to my eyes.

But the SFL feels like I'm looking through a larger porthole or at least my eye is closer to the 'display', even tho the image portrayed is the same. Or at least that's the way I perceive it. Are you saying that if I'm seeing the full view (field stop just on edge of 'hard'), the view formed on my retina is still diff?

This is a pretty interesting topic - I'm no optical designer, but think several factors are at play here.

ocular lens size - I agree this generally seems larger in many modern binoculars and recall reading somewhere that (as Swedpat mentions) it has to with eye relief, which modern designs tend to have more of these days. There is also (I think?) a relationship between ocular lens size and field of view. I think larger ocular lenses are positively viewed by many of us as we are conditioned to think more glass = better. But so long as it is wide enough to deliver the exit pupil is delivered to your eyes, the diameter of the ocular lens should not really matter. I have two Zeiss 8x30 porros, the 'B' model with a narrow 110m field of view and the non-B with 150m. The eye lenses of the non-B, which has very little eye relief, are significantly smaller. Go figure...

The 8x40 seeming much 'bigger' might be an effect of the larger exit pupil. I notice something similar when going from a 4mm to a 5mm exit pupil, and anything larger is almost incredibly effortless and comfortable.

The other factor is that with some binoculars you can place your eye closer to the glass, and in so doing "move the field stop further out", than others without getting blackouts, or before blackouts start to happen. This gives the impression of a wider view even if the FOV is not that great. There is a relationship with eye relief here, in that binoculars with long eye relief require you to move the binocular further from your eyes (via spacing the eyecups or other means), otherwise blackouts will happen. But differences between eyepiece designs probably also affect this as well. With one of my porro binoculars (Leitz 8x30) I can move that field stop a little "further out" than with the Zeiss West non-B, and I've always found it a little more satisfying to use for that reason despite both binoculars having the same FOV (which I've checked on landmarks etc).

Anyhow - just some random thoughts. I think our experiences all show how individual binoculars can be in terms of which ones fit best with our eyes.

 

[henry link]

The relationship between eyelens diameter, eye relief and apparent field of view has been discussed here a few times. The geometry is simple.

The Zeiss SFL 8x30 compared with select current 8x30/8x32 roof binoculars

Size and weight ; the retro more equal to a 8x30. According to B&H: SFL 8x30: 459g Leica 7x35: 590g SFL 8x40: 641g So the 7x35 are much closer to the 8x40. Length is: SFL 8x30: 11.9cm Leica 7x35: 13.2cm SFL 8x40: 14.5cm So the 7x35 are exactly in the middle.

www.birdforum.net

 

[MiddleRiver]

The relationship between eyelens diameter, eye relief and apparent field of view has been discussed here a few times. The geometry is simple.

The Zeiss SFL 8x30 compared with select current 8x30/8x32 roof binoculars

Size and weight ; the retro more equal to a 8x30. According to B&H: SFL 8x30: 459g Leica 7x35: 590g SFL 8x40: 641g So the 7x35 are much closer to the 8x40. Length is: SFL 8x30: 11.9cm Leica 7x35: 13.2cm SFL 8x40: 14.5cm So the 7x35 are exactly in the middle.

www.birdforum.net

So if two bins have same AFOV, the one with the larger eye-lens dia will provide greater ER. Got it. That's consistent with my 8x30SFL and 8x32FL.
Question: if user needs (random numbers) 15mm ER but bins provide 20, and assuming user keeps optical axis in perfect alignment with eye etc., what is perceived different or what are the effects of moving from 15 to 20mm? I assume you'd see the fields stop in both cases, but one image would look 'bigger' if only because of peripheral vision? i.e. assume eye is kept fixed. Is THAT why i perceive the one with 'excess' ER to be 'a bigger picture'?

 

[Paultricounty]

Don't know. And not having luck finding it.

It sounds like I'm not understanding FOV... And I'd love someone to explain AFOV to me and why - with what I think is the same 'view' - one design can seem more or less peephole than another.

MiddleRiver, this may help , and it’s what I go by for an explanation of FOV and AFOV. It was written by Henry Link years ago, I saved it in my binoculars file, so he gets all the credit here.

“
The real field is that slice(in degrees) of the 360 degree real world that the binocular or telescope takes in. I like that system better than the meters at 1000 meters specification because it can easily be converted to apparent field by simply multipling the real field by the magnification. So an 8x binocular with a 7.5 degree real field has an apparent field of 60 degrees(8x7.5=60).

Maybe you can think of it like this. When you're looking through the binocular, all the stuff in the real field appears to be 8 times larger than it really is, so the field itself must appear to be 8 times larger than it really is, thus "apparent field", the size the field appears to be to the eye.

It's useful because it tells you immediately, without the need to refer to magnification or real field or anything else whether the binocular or eyepiece in question has a "narrow", "standard", or "wide" field. Apparent fields of perhaps 38 to 48 degrees are narrow, mostly only encountered at the low magnifications of zoom eyepieces now. 50-55 used to be considered standard, but I think in binoculars most people prefer a wider apparent field than that now. Wide fields go from about 58 to 72 in birding optics. Most wide field binoculars fall between 60 and 65”

Paul

 

[Paultricounty]

The relationship between eyelens diameter, eye relief and apparent field of view has been discussed here a few times. The geometry is simple.

The Zeiss SFL 8x30 compared with select current 8x30/8x32 roof binoculars

Size and weight ; the retro more equal to a 8x30. According to B&H: SFL 8x30: 459g Leica 7x35: 590g SFL 8x40: 641g So the 7x35 are much closer to the 8x40. Length is: SFL 8x30: 11.9cm Leica 7x35: 13.2cm SFL 8x40: 14.5cm So the 7x35 are exactly in the middle.

www.birdforum.net

Hi Henry, I couldn’t find the link from your post of an old discussion on FOV/AFOV, hope you don’t mind I copied and pasted.

Paul

 

[Declan Joseph Deasy]

A related question: what is Zeiss’s flagship binocular? SF 8x42?

 

[MiddleRiver]

A related question: what is Zeiss’s flagship binocular? SF 8x42?

Just based on retail $, I would say yes. Based on IQ some might argue otherwise.

 

[Maljunulo]

Just based on retail $, I would say yes. Based on IQ some might argue otherwise.

Image Quality?

 

[Maljunulo]

Threads like this are always fascinating and intriguing.

Of all the subjective topics we discuss here, whether or not something is “worth it” surely is among the most subjective. Not only does it involve the usual variations in how our individual brain processes an interprets the inputs from our individual senses, it incorporates our views of money (its value) and how much of it we have.

All in all, a quantity which is completely impossible to measure, let alone agree on.

 

[Ignatius]

Image Quality?

Could always be the other one.