East meets West – 10x Binocular Challenge
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Arguably the most popular binocular for western hunting is the venerable 10x42, ask almost any hunter and they probably have at least one 10x42 in their lineup, but what makes this magnification and objective sought after almost more than any other? I would posit that it is a combination of both the magnification – 10x being somewhat of a sweet spot especially in hunting regions with more wide-open spaces along with the objective size of 42mm offering a unit that doesn’t weigh too much but still provides a 4.2mm exit pupil, as well as the weight being kept to a reasonable level. For many reasons, having a 5mm exit pupil is more ideal for overall performance; however, most 10x50 binos are a bit on the heavy side and for this reason, I think a lot of hunters have skipped over this option. But what if I told you that there was a new 10x50 bino on the scene using premium Japanese glass that doesn’t weigh any more than one of the best Austrian 10x42’s on the market, and what if I further told you the new bino was also designed by a German manufacturer, would you be interested?
I think many would be at least curious if a 10x50 bino with the benefits of the larger objective but without the extra weight could compete with the venerable 10x42.
THE BINOCULARS
If I were to put up a poll and ask “which is the most popular 10x42 binocular on the market today” more than likely the majority would say, “the Swarovski EL 10x42”. Yes, Swaro has a new NL Pure but many still prefer their EL’s and yes, Zeiss has their Victory SF and Leica has their Noctivid but, by and large, it is Swarovski that appears to win the popularity contest and likely due to the Swarovision flat field lens technology which improves edge to edge performance, but this "flat field" also bothers some people who pan a lot. All our eyes are different, so it's good to have options. Regardless, I chose the Swarovski EL to represent some of the best glass from the “west”. In comparison, the Japanese have been making some pretty phenomenal glass (for sport optics) for the past 5ish years that have really given the German/Austrian (G/A) glass a run for their money; one of the best examples of this has been the LOW 6-36x56 scopes compared to some of the best FFP scopes on the market – true, the best is still the “best” but for less than half the cost (in some cases) the Vortex RG3, Zeiss LRP S3 and Element Theos are not that far behind. For this reason I have been curious if similar quality glass would be made available in the binocular lineup, which brings us to the primary optic for this review – the Zeiss SFL 10x50 is a brand new design from one of the best German sport optics manufacturers, but what is unique about their SFL line is that they are using some pretty premium Japanese glass and construction for a lighter weight design than is typical for the objective size and offered at a more “affordable” price than the premium German lineup.
As with my scope reviews, this review will cover the optical and mechanical characteristics of the binoculars with a few tweaks appropriate to the differences between binos and rifle scopes. The same bias is still at play, there are certain characteristics and features that my eyes prefer so throughout my review you will see me make mention of those items to better help you decide if what I “see” will be an issue for you. Also similar to rifle scopes, it is very important that you setup the diopter correctly and binos can be a bit tricky, but in general most binoculars have only one diopter adjustment and it is usually on the right barrel (with the Swarovski the adjustment is on the face of the center focus wheel but still controls the diopter of the right barrel), some mfr’s offer a locking diopter which is usually a pull (to unlock) and push (to lock) design. To adjust the diopter correctly it is generally recommended that you find an object about 50 yards away and cover the right barrel (with the lens cover or other object), keep both eyes open and look through the binoculars, you will only see the object through the left barrel/left eye and you will adjust the focus wheel until the object is as sharp as possible (recommend putting the binos on a tripod or other stable platform so you are not battling hand shake), once you are confident the left barrel is in ideal focus, cover the left barrel and open up the right barrel (be careful not to touch or bump the focus wheel) – now look at the object which will now be viewed through only the right barrel/right eye and now simply adjust the diopter until the object is in ideal focus, once done you can lock or mark the diopter for future reference but once you uncover both barrels the object should be in ideal focus for both your eyes. If you do not set your diopter correctly (for either rifle scope or binocular) you can have the best glass in the world and may not be very impressed so it is critical that you get this right from the beginning.
SPECS
The below specs are provided by the manufacturers which provides a good baseline for what these binoculars offer and how they compare.
| Manufacturer: | Swarovski | Zeiss |
| Manufacture Country | Austria | Designed in Germany, Made in Japan |
| Model: | EL | SFL |
| Glass: | Schott | Japanese UHD |
| Lens Type: | ED Fluorite (FL) | UHD |
| Prism System: | Schmidt-Pechan | Schmidt-Pechan |
| Coating: | SWAROBRIGHT, SWAROTOP, SWARODUR, SWAROCLEAN | LotuTec® / 6-Layer T* |
| Magnification and Objective: | 10x42 | 10x50 |
| Fogproofing: | Nitrogen Purged | Nitrogen Purged |
| Waterproof: | 13' water depth | 400 mbar |
| Reticle (Mil/MOA): | No | No |
| Exit pupil diameter (mm): | 4.2mm | 5.0mm |
| Eye relief (mm): | 20mm | 18mm |
| Field of view (ft/1000 yds): | 336 ft | 366.0 ft |
| Close Focus (ft / m): | 4.9 ft | 5.9 ft |
| Length (in / mm): | 6.3 in | 6.3 in |
| Width (in / mm): | 5.2 in | 5.2 in |
| Height approx. (in / mm): | 2.4 in | |
| Weight (oz / g): | 28.0 oz | 30.8 oz |
| Warranty: | Limited Lifetime Warranty. Limited 2-Year Electronics Warranty | Lifetime for any owner. 5-year first owner accidental. |
| Special Features: | Swarovision flat field technology. Large eye relief with close focus. Some don't like flat field for panning with BIF. Fantastic DOF with stunning IQ. Unparalled edge to edge sharpness.
The new EL has "Swarovision" (SV) which is just a marketing term for a field flattener and ED-glass.
The older ELs had a more traditional optical design, especially in the eyepiece. The SV has a slightly different appearance than the older EL. The SV has green on the inner barrels between the hinges, while the older EL was all black in that area.
The older EL was a very good performer. The new EL SV suppresses chromatic aberration better and has a sharper edge. | Extremely wide FOV for a 50mm objective. The SFL binoculars are up to 30% lighter than comparable products from competitors. Field flatener lens. HT lens for 90% transmission. |
MECHANICAL ASSESSMENT OF FOCUS WHEEL AND DIOPTER
Unlike riflescopes, there are fewer moving parts with a set of fixed magnification binoculars. The diopter should really be a set it and forget it option (however, if you are going through a lot of eye issues or changes it would be a good idea to check diopter every once in a while and especially if you have eye surgery). So the main mechanical feature is the focus wheel itself.
Mechanical Assessment criteria (ratings: = (equals) > (greater than) ranked highest to lowest):
Focus Wheel Adjustment ranking:
Zeiss SFL 10x50 = Swarovski EL 10x42
Both feel very refined with smooth adjustment, neither felt too tight or too loose, I would consider both to be ideal.
Focus Wheel Adjustment Forgiveness ranking:
Swarovski EL 10x42 > Zeiss SFL 10x50
What exactly is focus “forgiveness”? I define this as how much or how little you have to mess with the focus wheel at varying distances. The less you have to mess with the focus wheel the better (more forgiving), and the more you have to mess with the focus wheel is worse (finicky).
Diopter Adjustment Rankings:
Zeiss SFL 10x50 > Swarovski EL 10x42
The Swarovski has an interesting diopter adjustment point as it sits on the face of the focus wheel itself, it is not the easiest to adjust but gets the job done as a set it and forget it type of setting. The Zeiss has the more traditional diopter setting right in front of the right side eyecup and is the easier of the two to setup IMO.
Eye Cup Adjustment rankings:
Zeiss SFL 10x50 = Swarovski EL 10x42
Due to the short eye relief design of binoculars you have to get them up close and personal and for eyeglass wearers that could be an issue so most manufacturers give you adjustable eyecups. Both Swarovski and Zeiss use a design with 3 main adjustment notches and you can choose what is most comfortable while offering the largest sight picture possible. Both units were easy to adjust and for the most part held their position with multiple use.
Overall Side Focus and Diopter Mechanical Assessment Rankings:
Swarovski EL 10x42 >= Zeiss SFL 10x50
All things considered the two are pretty closely matched; however, I would say the Swaro has the slight advantage due to having greater focus forgiveness.
OPTICAL QUALITY
One of the most debated topics among the forums with regard to sport optics is how “good” is the glass in any particular optic. There are many things that can affect how our brain perceives the image through an optical lens and since we all tend to “see” things a little differently optical quality can be somewhat hard to quantify; however, I think I have a pretty good review formula that breaks down some of the different nuances of optical characteristics along with my personal preferences in each category to hopefully give you a better idea of what I’m seeing and how you might agree or disagree based on your own preference.
Optical Assessment criteria (rating lower numbers are worse and higher numbers are best):
Pop (Combination of Color, Contrast and Clarity) on resolution chart
Pop is the ability for the image to really stand out and come alive. This is the overall impression your brain receives when first looking through the optic (bearing in mind that you must have the diopter setup correctly to begin with, if you look through someone’s optic at the range which was setup for their eye then you are shortchanging yourself and possibly get a false sense of how well the optic could perform if properly setup for your eye).
Pop (Combination of Color, Contrast and Clarity) at distance >500y
How well does the overall image look when viewing objects at distance. Sometimes I have seen some optics perform very well closeup but not so great at distance and vice versa.
Contrast (High)
My high contrast target has very bright white paper with very black lines, the numbers represent the smallest value I am able to discern.
Contrast (Low)
My low contrast target has a gray background with darker gray lines, the numbers represent the smallest value I was am to discern.
Chromatic Aberration (CA) Center
A hotly debated topic – CA, which is typically seen at the edges between high and low contrast objects in what is termed fringing and usually comes in a band of color along the green/yellow and magenta/purple spectrum, some are greatly annoyed by this optical anomaly while others insist they cannot see it, one thing to know is it has little to do with your ability to hit a target, but can affect the clarity of the target (especially in lower light situations). I tested for both center CA and edge CA. One other area is CA sensitivity with lateral movement off the center of the scope, you can quickly induce CA in these situations which are often rectified by proper eye placement behind the center of the optic.
Chromatic Aberration (CA) Periphery/Edge
Many scopes may have really good performance in the center of the image, but quickly fall apart as you move toward the edge of the image which can affect your ability to accurately see and define objects towards the edges.
Color Accuracy
If you’ve ever heard the term “it’s all in the eye of the beholder” that in large part describes the experience of color for each of us. It seems our eyes have different sensitivity to different parts of the spectrum and while I tend to prefer “warmer” images and am somewhat put off by “cooler” ones, others see colors differently.
Resolution (Center)
This is different from my line resolution testing, this is how “sharp” the image appears, I’m looking for details and the optics ability to resolve those details.
Resolution (Edge)
Same thing as center resolution but now I’m focusing my eye at the extreme edge of the sight picture and determining if there is any image degradation that occurs toward the edges. An optic can have very sharp center resolution but poor edge sharpness and it will give the user the impression that the overall quality is not very good.
Resolution (Edge) at distance >500y
I added in this test because I was beginning to notice that some scopes did not perform so well in the close testing but seemed to do better at distance, I still prefer an optic that has superb edge to edge sharpness, but found that some optics did not bother me as much as I thought they would at distance.
Eyebox Forgiveness
Eyebox with binoculars is a bit different from that of rifle scopes due to different designs within each, the nature of the design of the binocular with shorter eye relief than most rifle scopes along with eyepieces that are designed for you to rest your brow against (or at least close to). That said, there is still an advantage with some designs over others and they just “feel” easier to get a good sight picture.
Depth of Field (DOF) Forgiveness
DOF forgiveness is the ability to have both near objects as well as far away objects appear “in focus” in your sight picture. An example would be to set your focus at some far distance and you notice that both an object that is closer as well as one that is further look relatively in focus.
Focus Forgiveness
How much, or rather how little, do you have to play with the focus wheel in order to get an object in focus as you change distance.
Mirage (effect)
This is another one of those terms that requires a definition. Mirage occurs because light bends to move through warmer, less dense air, this “bending” of light is the effect we see when our target appears to dance or wobble in the distance, we know the target is stationary but as the heat waves rise from the ground, the light is bent and gives the perception that the image is distorted. What I am looking for here is the ability of the scope to tame or limit the effect of mirage, within the community this is often referred to as “cutting through mirage” and some optics handle this situation better than others. Keep in mind that my results are based on what I saw on the particular day I was testing; however, different atmospheric conditions can either decrease or increase the effect of mirage by quite a large margin.
Optical quality Test Results (higher numbers are better)
Field of View (FOV)
With rifle scopes FOV can be tricky because manufacturers list FOV at only two settings – the bottom and the top magnification making the middle of the range hard to evaluate, but the vast majority of binoculars are fixed magnification so the FOV should be accurate if the manufacturer did their due diligence. There has been a growing trend of offering optics that provide greater FOV and Zeiss’s latest shows just that, offering what I believe is the most FOV of any premium 10x binocular on the market.
| Mag | Zeiss SFL 10x50 | Swarovski EL 10x42 |
| 10x | 366’ @ 1000y | 336’ @ 1000y |
Twilight Transmission (low light performance)
From about 20 minutes after sunset, I begin testing both binoculars side by side as the evening becomes darker and darker. These results are very subjective and as I have aged, I believe my eyes low light acuity has decreased. You may have very different results depending on your age and how good your eyes are. What surprised me in this test was how well the Swarovski did with only a 4.2mm exit pupil vs. the Zeiss’s 5mm exit pupil and it wasn’t until the very last of low light that I felt the Zeiss actually had an edge. Swarovski has better depth of field and better focus adjustment whereas the Zeiss has less depth the field and requires more finicky focus adjustment, but not terrible. Swarovski 42 mm objective holds its own in low light and only until the darkest light after sunset is where the Zeiss has a slight edge.
Resolution Line Chart (LPI)
It’s one thing for me to look through an optic and judge resolution based on a 1-10 ranking, but it’s quite another to look at line charts and determine how many lines I’m able to resolve at a given magnification, my resolution testing above is a good “first impression” but the line chart does not lie and provides a more quantitative result. For most results you’ll see a range – it is hard to resolve exact values with your eye and I would try to narrow it down as best I could but sometimes eye strain, perfect alignment, etc. would get in the way.
Other factors:
Sight Picture (HD)
- ZEISS SFL 10X50: Very good image.
- Swarovski EL 10x42: Excellent image.
Outer Periphery
- ZEISS SFL 10X50: Somewhat thick periphery but thinner than Swaro.
- Swarovski EL 10x42: Pretty thick periphery.
Flare/Halation (direct sun on objective at 10x)
- ZEISS SFL 10X50: Very little whiteout, excellent image fidelity with only a minor spot. I also tested with the sun behind the eyepiece and did not find any red hue that some have claimed occurs with Zeiss’s LRP line of scopes.
- Swarovski EL 10x42: Image gets washed out pretty easily, whiteout in image appears opposite of the light source location (so if the sun is in the upper left corner the whiteout will appear in the lower right section of the sight picture.)
Overall Optical Assessment Results:
Swarovski EL 10x42 >= Zeiss SFL 10x50
I happen to be one of the people who like/prefer the Swarovision flat-field technology which offers very sharp edge to edge performance, I do happen to pan with my binos as I not only use them for hunting but also for birding where I’m scanning back and forth looking for critters, as such I definitely lean towards the Swaro’s for this reason; however, the minimal edge distortion and wider FOV of the Zeiss SFL never really bothered me or caused me to feel that my FOV was hindered, it is a very well done design especially at its price point. In the end, the more expensive Austrian glassed EL has the edge, but like I’ve seen with rifle scopes and the RG3, I saw here as well, the Zeiss with the Japanese glass is not far behind at all and in some areas (like distance and halation) I actually felt the Zeiss performs better; let me clarify, at distances beyond 500 yards I felt the Zeiss actually resolved the image better providing more micro contrast detail than what I saw through the Swaro EL, this surprised me.
ERGONOMICS
Overall Ergonomic Assessment Results:
ZEISS SFL 10X50 = Swarovski EL 10x42
The overall ergonomic assessment is based on the features of the optic, how intuitive are they to use, how easy are they to manipulate. The hinge on both are outstanding and provide the right resistance allowing for proper pupil spacing without easily moving off the adjustment. Both focus wheels are easy to access from left or right hand and manipulate. Both eyecups are easy to set without fear of them getting bumped out. Both feel very good in the hands so I would rank this as a tie.
FIT & FINISH
Overall Fit & Finish Assessment Results:
Swarovski EL 10x42 > ZEISS SFL 10X50
What I’m looking for here is quality of the finish, how each piece interacts which each other, materials used and function as a working whole. I feel the Swarovski takes the overall victory in this category while the Zeiss is truly not far behind. I would say the rubber armor on the Zeiss is maybe a little “too rubbery” and tends to collect and hold dust a little more (this can actually be seen in some of the pictures). This has nothing to do with performance of the binocular as a whole but this is the fit and finish section and I think Swaro has slightly better finish on their EL.
AREAS OF IMPROVEMENT
Zeiss SFL 10x50
As mentioned above, the rubber armor has a tendency to hold dust a bit more making it a bit more difficult to keep clean. I would like to see Zeiss offer some type of flat field lens or improve upon the edge distortion some.
Swarovski EL 10x42
There is a reason the Swarovski EL is considered one of the best binoculars made, there is very little to find complaint in. I suppose it would be FOV, but Swarovski has addressed this in their (uber expensive) NL Pure line which offers best in class FOV but at 1.5x the cost of the EL.
FINAL THOUGHTS
The new Zeiss SFL 10x50 is a remarkably good design for the price, offering premium optical performance at almost half to more than half the cost of the competition. That along with the fact that you get 42% larger objective size while being the same length as the Swaro 10x42’s and not weighing more than most of them either, along with the fact it has one of the best FOV numbers out in a 10x design… this is a win win in my book. The Zeiss SFL offers brilliant pop, brightness and overall experience at an amazing street price. If you want one of the best then get the Swarovski, but you’re going to pay more for it and if you spend a lot of time looking into sunsets or sunrises you may find it frustrating due to flare. What this confirms for me is that the latest premium glass coming from Japan is very, very close to the very best glass from Germany/Austria (G/A) and offers some quality’s that might actually benefit you more than overall quality of the best G/A glass. If you want brilliant edge to edge sharpness then Swaro is your choice but if you want more accurate color, wider FOV, brighter image for lower light and better micro contrast at distance then I honestly think Zeiss is the choice. But the choice is yours, and I do not think you cannot go wrong with either.
