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Where premium quality meets exceptional value. ZEISS Conquest HDX.

Zeiss SFL 8x40 review from Australia (2 Viewers)

mgp13

Well-known member
Australia
Although many reviews of the Zeiss SFL have been posted, I'd like to share my quick perspective from using the 8x40 variant in southern Australia. This review is based on two weeks of intensive field use.

To begin with, the first thing I noticed about the field is its brightness. The view through these binoculars is beautifully bright and yet they mostly remain easy on the eyes. After two hours using these binoculars to scan a reflective lake at midday I noticed only slight eye fatigue. Only when looking directly at the sun's reflection on the water did I feel any discomfort. I have not sampled all the binoculars available on the market but I'm inclined to believe the brightness of these binoculars in the 8x40 variant is on par with the best. Flowers and foliage are beautifully rendered, as are the yellow highlights of the locally abundant New Holland Honeyeater. The pale eye of this species reflects gorgeously through this binocular at close range, something I did not appreciate as much through my Leica Trinovid HDs. Zeiss claim 90% light transmission for the SFL and I certainly can't argue with that. My mind boggles thinking there are binoculars out there that achieve 91-92% or more, and I imagine any benefit of that must exist only in very low light. In any daylight the SFL with 90% transmission is more than bright enough for birding.

The next thing I noticed about the view and which also puts this binocular above the Leica Trinovid HD from which I upgraded is the contrast. It is immensely satisfying to see blacks rendered in such an inky tone. Looking into some bushes, the bright green of the foliage contrasts beautifully with the darkness of the branches beneath. I also found myself benefiting from the contrast when viewing quite distant shorebirds. The SFL easily separates browns from blacks even under challenging lighting conditions. In all conditions the contrast is simply superb and is a clear stand-out feature of the view through the SFL 8x40.

The clarity is absolutely outstanding. Again it gives the SFL 8x40 a clear advantage over the Leica Trinovid HD (I should add that while I don't consider the comparison completely fair, since the SFL is more of an alpha contender and much newer to the market, these two binoculars retail for a similar price in Australia. The SFL 8x40 retails for about $1480 USD in Australia, compared to $1350 USD for the Leica Trinovid HD in either 8x42 or 10x42. Zeiss Conquests retail for around $1150-1250 USD here). Birds and vegetation are rendered stunningly sharp through these binoculars, particularly once one has a feel for the Smart Focus mechanism. Again I am inclined to think the clarity and sharpness is among the best available - I struggle to imagine how it could be much better.

Much is made of Leica's unrivalled ability to render colours but the Zeiss SFL is virtually on par here. Yellows and reds do not "pop" to quite the same extent but colour rendition is nevertheless quite outstanding and clearly better than any non-Leica binocular I've tried. I would describe the colour rendition as extremely accurate and only very slightly over-saturated (in a good way) compared to a natural naked-eye view. While the Leicas may have the edge in sheer colour rendition the Zeiss SFL offers the better view due to its brightness and contrast. Ultimately it offers the more attractive view of the two. I highly doubt anyone could fault the colour rendition of these binoculars, even long-time Leica users. I am inclined to think the superb contrast and colour rendition must owe something to the state of the art coatings of these particular optics.

I had to push hard to detect any chromatic abberation in the view through these optics - mostly it is completely absent. To detect trace amounts of CA I had to really look for it, and even then it was minimal. It is safe to say CA should not be an issue for most users of this binocular. I have to add that CA is not something that ever bothered me with the Leica Trinovid HD despite the reputation of this variant for high levels of CA. It is something that only becomes obvious under unusually harsh lighting conditions in any case.

The field of view of the SFL 8x40 (140m @ 1000m) is very immersive and is more than enough for most users of binoculars, except perhaps those who are habituated to the 155-159m offered by the very latest Swarovski and Zeiss variants. I am highly impressed by the largely flat field and again I suspect it is only Swarovski EL and NL users who could possibly find anything to complain about in terms of edge sharpness. The edge sharpness of the field blows the Leica Trinovid HD out of the water and if the inclusion of "Field Flattener" technology in the SFL is the reason for this then I think it's fair to say It's likely superior to that of the Zeiss Conquest also. "Rolling ball" effect is almost absent due to some minor edge distortion although under some long-distance viewing conditions it can be noticed if one is really looking for it.

The depth of field is quite spectacular through the SFL 8x40 and means one will not miss potential bird activity in the near background of the image. Only very small adjustments of the Smart Focus wheel are required to bring that background into view. The result is a feeling of immense ease in using these binoculars. On the downside for some, the very deep field produces ugly bokeh in most conditions. I personally find this preferable to the shallow field and blurry background ("good" bokeh) of the Trinovid HD. In a camera, ugly bokeh is undesirable but in a binocular it makes sense - the deeper the field, the better.

The ergonomics of the SFL 8x40 are a standout and in my opinion an area where this binocular has a clear advantage over most binoculars on the market. The light weight (640g) and long barrels combined with the position of the Smart Focus wheel give these binoculars a supremely easy and comfortable feel in the hand. This model also excels at one-handed use - I was easily able to follow swallows in flight while I had one hand on my tripod over my shoulder. It gives me reason to believe the SFL is particularly well suited to being an 8x. I imagine the 10x40 would not offer quite as stable or wide an image for one-handed use.

I absolutely love the Smart Focus system. The smallest and finest adjustments are required to bring subjects into perfectly sharp view. Switching from near focus to very distant focus has perhaps never been easier in a binocular, with only a few nudges of the focus wheel required. The wheel itself also has an immensely satisfying, easy and yet high-quality feel to it.

Build quality seems excellent across the board and the binoculars feel very well-built. The eye cups are sturdy and comfortable and the twist mechanism has a high quality feel to it. However, I am able to tell these binoculars will not age as well as the outstandingly-built Leicas. I do believe Leica have an edge when it comes to build quality and I do wish Zeiss would try to take a leaf out of their book in this department. While the overall build of the SFL is certainly very good and non-Leica owners might even consider it extremely good, my own feeling is that at this price bracket the build quality should be absolutely without fault. The rubber armouring is attractive and no doubt durable, but will likely discolour with age, which is something that has never happened to my Leicas. The armouring attracts dust and fingerprints much more than the Leicas also. In all, the less-than-perfect build quality is the only thing about these binoculars I would change if I could.

Overall I am extremely happy with the SFL 8x40 and believe given their price they are extremely strong contenders for best value in a binocular. They offer a gorgeous and addictive view and supremely good ergonomics that together I believe must place them very close to the best alphas available. I foresee many years of enjoyable birding through this high quality glass. Thanks for reading this review.
 
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I should add that while I don't consider the comparison completely fair, since the SFL is more of an alpha contender and much newer to the market, these two binoculars retail for a similar price in Australia.
This sort of local variation must really vex manufacturers who've designed a model to a price point relative to others. I wonder what accounts for it.
The depth of field is quite spectacular through the SFL 8x40 and means one will not miss potential bird activity in the near background of the image. Only very small adjustments of the Smart Focus wheel are required to bring that background into view. The result is a feeling of immense ease in using these binoculars. On the downside for some, the very deep field produces ugly bokeh in most conditions. I personally find this preferable to the shallow field and blurry background ("good" bokeh) of the Trinovid HD. In a camera, ugly bokeh is undesirable but in a binocular it makes sense - the deeper the field, the better.
As the only other one here who's mentioned "ugly bokeh" in SFL I'm glad to see it brought up again. I agree that it seems "busy" rather than "smooth", but actually this means only an illusion of greater DOF (which depends only on magnification). At 10x, I felt it became difficult to know what I had focused on, especially in a busy/leafy environment. (The fact that things look less blurry doesn't mean they're actually sharp.) SFL is the only binocular in which I've ever noticed this, so the question arises whether it was deliberate or somehow just the result of other optimizations. I hesitate to imagine that Zeiss were actually trying to give a misleading impression of greater DOF than competitors.
 
This sort of local variation must really vex manufacturers who've designed a model to a price point relative to others. I wonder what accounts for it.

As the only other one here who's mentioned "ugly bokeh" in SFL I'm glad to see it brought up again. I agree that it seems "busy" rather than "smooth", but actually this means only an illusion of greater DOF (which depends only on magnification). At 10x, I felt it became difficult to know what I had focused on, especially in a busy/leafy environment. (The fact that things look less blurry doesn't mean they're actually sharp.) SFL is the only binocular in which I've ever noticed this, so the question arises whether it was deliberate or somehow just the result of other optimizations. I hesitate to imagine that Zeiss were actually trying to give a misleading impression of greater DOF than competitors.
You lost me… bokeh (variation) in binos?
I thought we’d agreed DOF was set by magnification.
Looks like I need remedial review of a bunch of old threads!
 
Nice smooth bokeh behind the point of best focus is just a positive way of saying that an optic is spherically over-corrected. That may be OK in the case of fast medium resolution camera lenses, but it's quite undesirable in high resolution telescopes. Well corrected telescopes (and binoculars) should show identical (and not especially smooth) bokeh on both sides of focus, reflecting identical diffraction patterns both inside and outside of focus.

In the real world most binoculars and spotting scopes have low focal ratio objectives that are under-corrected, with diffraction discs in front of focus showing bright centers that grow dimmer and softer toward the disc edges. That's the kind of diffraction disc that produces smooth bokeh. In that case there will always be hard bokeh on the other side of focus made from diffraction discs with dim or missing diffraction rings in the center that grow brighter and harder toward the disc edge. Whether the smooth bokeh is in front of focus (under-corrected) or behind focus (over-correction) it's always a good indiction of of a bad thing - high spherical aberration.
 
Sure enough, background bokeh tends to be a bit uglier than foreground in binoculars. So perhaps Zeiss really nailed spherical correction in SFL, but why do so many others tend to be under-corrected -- does this involve challenges of aspheric grinding?
 
Nice smooth bokeh behind the point of best focus is just a positive way of saying that an optic is spherically over-corrected. That may be OK in the case of fast medium resolution camera lenses, but it's quite undesirable in high resolution telescopes. Well corrected telescopes (and binoculars) should show identical (and not especially smooth) bokeh on both sides of focus, reflecting identical diffraction patterns both inside and outside of focus.

In the real world most binoculars and spotting scopes have low focal ratio objectives that are under-corrected, with diffraction discs in front of focus showing bright centers that grow dimmer and softer toward the disc edges. That's the kind of diffraction disc that produces smooth bokeh. In that case there will always be hard bokeh on the other side of focus made from diffraction discs with dim or missing diffraction rings in the center that grow brighter and harder toward the disc edge. Whether the smooth bokeh is in front of focus (under-corrected) or behind focus (over-correction) it's always a good indiction of of a bad thing - high spherical aberration.
Thanks for this elaboration Henry. Have wondered about the term, and hoped for some sort of diagram to help with my struggle to get from unfamiliar technical terminology to something a bit more ah... clear, in focus. Went to Google, found this:

Bokeh - Wikipedia.

Many years ago, was into Macro, very close up photography of technical details of things and recall these descriptions as then desirable techniques for that sort of photography. This well before 1997. The various diagrams there help with your point this not good stuff in scope or bino.

I have question re spherical aberration. I'm thinking about a granite inspection plate I own, used for machining applications, that came with a chart describing how perfectly flat, it was/wasn't, over its entire surface called out. With the term spherical aberration for a lens, are we talking the whole curve of the lens being correct or not? Or is it the case the desired curved surface has variation here and there, (like that inspection plate) that causes aberration? Or both?

Whats the difference between smooth and hard Bokeh?
 
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