Review: Zeiss SFL (SmartFocus & Lightweight)

It's been a while since I've posted a review, but the latest offering from Zeiss intrigued me, so here we go!

Introduced in 2022, and available initially in just 40mm models, the Zeiss SFL caught the eye of many birdwatchers as they offered something rather different to other 'alpha' binoculars. While 40mm objectives were common many years ago, they have largely disappeared from the market in favour of 42mm models. According to Zeiss, reducing the objective lens diameter by 2mm has allowed them to use thinner lens elements at closer spacing, ultimately reducing the size and weight significantly compared to the likes of the Zeiss Victory SF or the Swarovski EL. Earlier this year, the 30mm models arrived, offering an even smaller and lighter option versus the 40mm models. In this review I'll be looking through all 4 options.

Optically, the SFL retains many of the best features offered by the more expensive Victory SF: superior field of view, field flattener technology, and Zeiss T* multi-layer coating. Even though the Japanese made SFL models lack the 'Ultra-FL Concept' and 'Schott HT Glass', which are present on the German made Victory SF, the SFL's 'Ultra-HD (UHD) Concept' replicates these coatings. That's a lot of jargon for anyone to take in, so I'll briefly explain what these do and how they affect the Zeiss SFL. The wide field of view perhaps speaks for itself, with the 8x models offering the widest image, but both 10x magnification models still putting up very generous views. Coupling this with field flattening technology means edge-to-edge clarity. Zeiss T* coatings improve the contrast and clarity of the image, while the UHD concept takes this a step further, resulting in an impressive 90% light transmission for all models.

Most importantly, what does this all mean in practice? Our ever-present flock of House Sparrows provide an opportunity to put the SFL to the test. In typical April style, the conditions are changing, but even as the grey clouds block out the sun, the SFLs provide a bright, punchy image. The colours are neutral yet vibrant - the chestnut brown back on the Sparrow looks vivid, while the contrast between the pale belly and black bib makes the bird really stand out in the foliage (good news for him). An interloping Dunnock skulks in the undergrowth below the holly bush, and again the SFLs offer a sharp, bright view. The field flatteners do a fine job, although not perfect; the edge of the image isn't as crystal clear as the centre, but the softening is insignificant. Try as I might, I can't see much colour fringing at all, which proves even without the fluoride lenses found in the Victory SF, chromatic aberration is controlled well by the UHD glass. In the afternoon, I'm hard pushed to notice any difference in brightness between the 30mm and the 40mm models. Even the 10x30, with just a 3mm exit pupil, appears as bright as the 8x40 with its 5mm exit pupil. Of course, this will vary depending on the user and their eyesight, and later into the day, the 8x40 will prove superior.

All models are quoted by Zeiss to achieve a superb 1.5m close focus - in my tests I found I could get marginally closer in fact with all models, between 1.3m and 1.4m. Anywhere under 2m would be considered very good, so these figures are remarkable. It's unlikely you'll find yourself often using them for subjects so close, but a lovely option none-the-less.

Moving on to build quality, it's reassuring the know the SFL are housed in a magnesium chassis, coated in a well gripped rubber armour. The exterior glass elements are protected by LotuTex dirt-repellent coatings. The eyecups are plastic, but stop firmly at each position, and are also threaded, which allows you to remove them for thorough cleaning. Should you ever need them, replacements are available from Zeiss and are easy to change without needing to send your binoculars away. The dioptre for individual eye adjustments is in the traditional position located under the right eyecup. Its not lockable, but is noticeably stiff, so it won't budge accidentally. The focus wheel sits inside the magnesium bridge, a feature not found on many binoculars, but this allows for far more natural finger placement when focusing. This is the key part of the 'SmartFocus' concept, combined with a smooth turning wide wheel which requires approximately 1.8 revolutions from close focus to infinity. Another smart feature is the position of the lugs where the strap attaches to. By moving this further up the body, these lugs don't interfere with your hands as I have noticed with other binoculars. This is often more of an issue for me with smaller binoculars, so it's refreshing to be able to use the 30mm SFL with great comfort. As previously mentioned these aren't manufactured in Germany, but rather in Japan. The build quality doesn't appear in any way inferior to the German made Victory SF, but you'll have to look elsewhere if you're after a European made model.

Ergonomically, because all models are so light, they aren't at all front-heavy and therefore balance very well in the hand. It's hard to overstate how much lighter these are compared to other 'top' binoculars, and I think it's the big selling point here. With the included padded neck-strap, even the 40mm models won't cause much discomfort at all on a long walk, but the sub-500g 30mm models are brilliant choice if you're hiking or travelling. Eye-relief should be more than adequate for most users, at 18mm for every model. As I don't wear glasses, I had the eyecups fully twisted up, and found them all comfortable to use.

The SFL models are presented beautifully in the box, and matched by the high standard of the included accessories. First to greet you opening the box is the soft, padded case, labelled as "100% recycled fabric", made from upcycled PET bottles. A detachable strap for the case is also included. The rainguard is snug but not too tight, while the objective covers tethers, once you've squeezed them over the barrels (noting they are labelled L for left barrel and R for right barrel), stay firmly in place. The actual covers then fit inside the barrels rather than outside, and hang well out the way when in use. Completing the accessories is a premium neoprene Zeiss branded lanyard, cleaning cloth and instruction manual. Zeiss offer the same 10 year guarantee with the SFL as they do with their German made models, another reassurance of their premium quality.

Scores:

Optical quality: 9/10
Build quality: 8/10
Comfort: 10/10
Accessories: 9/10
Value for Money: 9/10

Star Rating:

Conclusion:

All models offer something different, but ultimately should be on your list if you're looking for an 'alpha' binocular. Optically, the SFL only falls a fraction short of the incredible images offered by a Victory SF, Swarovski EL or NL, but these larger binoculars are considered too cumbersome by many. The 40mm SFL, weighing just 640g, is in fact not at all dissimilar to the weight of the 32mm Victory SF or NL Pure, while offering a larger exit pupil. I was impressed by each model, notably just how comfortable they are in the hand. It's hard to be too critical, but metal eyecups and a lockable dioptre would have been nice features, on an otherwise compelling pair of binoculars.

Technical Data