Zeiss 7x42 Dialyt ClassiC Review

Forty five years ago, in 1981, Zeiss released what would become one of its most iconic and celebrated products, the 7x42 Dialyt birding binocular. The 7x42 Dialyts remained in production for the next twenty years, finally discontinued in 2004.

I ended up with a late pair as my first high-end binoculars at the very end of last century, an insurance company direct replacement for a smaller pair, the only Zeiss bino’s they stocked. By then, the Dialyts, with their long barrels, external focusing and thick black armour, seemed an oddity compared to the new vogue in small roofs. I didn’t choose them, never understood them and hardly used them. I sold them as new for less than £300 and bought some small roofs with the proceeds.

In recent years, though, I’ve noticed people extolling their virtues on the forums - virtues like a wide field, long eye relief and a bright view, that I value too. Meanwhile, the used price of Dialyts now far exceeds what I got for mine sixteen years ago. What’s going on? Is this just nostalgia or something more profound? As part of my fresh look at Zeiss products for 2021, I thought I should get a pair and find out ...

At A Glance

Magnification	7x
Objective Size	42mm
Eye Relief	16-18mm (depends on cup fold)
Actual Field of View	8.6
Apparent field of view	~60°
Close focus	~3m
Transmissivity	?85%
Length	190mm (eye cups extended)
Weight	800g measured

Data from Me.

What’s in the Box?

I unearthed a couple low-res photos of the display box for my original pair of ClassiCs:

Design and Build

Though the 7x42 Dialyt was introduced back in 1981, it was based on a design that went back much further, almost to start of the century. To me, Dialyts look like a Steampunk hybrid of the external-focusing bridge of a traditional porro prism binocular and the long straight barrels of a pair of roofs. Partly that curious shape is due to the prisms, on which more anon.

Despite their long production run, the 7x42s were not the last Dialyts to remain in production. The similar but even longer 8x56, favoured by hunters and deer stalkers, continued until around 2016.

The pair on review here is a late example, branded ‘ClassiC’, but it’s basically the same binocular as a 1980s pair, albeit with some vital but hidden improvements. Again, more on that below.

Body

The Dialyts have a unique look that I’ll admit I didn’t like in that first pair I owned over two decades ago. Back then I was a consumer of mobile phones, laptops and fast cars; to me the Dialyts had a curmudgeonly, even fugly appearance.

Now the Dialyts look retro and utilitarian, but in a good way, with that thick black rubber armour, long barrels and external focusing bridge. Whatever you think of their distinctive look, rugged they certainly are, with this pair clearly having had masses of use (so much that someone’s thumbs have worn dents in the armour under the bridge).

There has been much discussion about how waterproof the Dialyts are, but the summary seems to be that though they are well sealed and generally rain-proof, they are certainly not purged and immersion proof like most modern birding bino’s. That means they can suffer from fogging and internal damp problems, like fungus, so they need a little more care when using and storing.

Despite being long, the Dialyts are not heavy. At 800g they weigh about the same as a pair of Zeiss 8x42 SFs, an advantage of their simple design.

Focuser

Mechanically, the focuser is clearly different from a pair of modern roofs. Instead of having a focusing lens inside the barrels, these have a bridge that moves the eyepieces like traditional porro-prism binoculars. It sounds primitive, but in practice confers some real advantages like simplicity and ruggedness, lower weight and less false colour.

Some moving-bridge focusers are a stiff and horrid. Not here. The basic action is superbly smooth, light and fluid, though this pair does stick occasionally due to age and wear.

At just over 3m, close focus is up to modern (if not the very best) standards. More importantly, it’s possible to get a very comfy merge at that distance. The focuser is fast too, at just under a turn from close focus to infinity. Unlike a modern focuser it has a scale, so you can re-set preferred positions.

Dioptre is adjusted by twisting the right eye piece, as for many bino’s.

Optics - Prisms

As I said in the introduction, these are neither a Porro-prism nor a Schmidt-Pechan (a.k.a. Roof) prism binocular. Instead, they feature a type of prism called an Abbe-König, that is long and thin and gives the binoculars their distinctive appearance. Abbe-Königs have a big advantage: like porros and unlike roofs, they don’t need mirror coatings, instead bending the light by total internal reflection. However, unlike porros, Abbe-König prisms do need phase-correction coatings to avoid loss of contrast and resolution. If you only read one line of this review before buying a pair of Dialyts, make it this one:

The Dialyts only got phase correction coatings at the end of the Eighties. Binoculars with this feature modern performance and will have T*P* on the front of the bridge in red that you see on this pair. Binoculars that don’t have phase coatings will give an inferior view, yet often carry a similar price tag. Beware!

Optics - Objectives

I had imagined the objectives to be triplets, especially given that the heavy curve on the front element suggests a short focal length. But investigation with a laser suggests that, no, they’re just a cemented doublet with the crown up front.

Internal build quality and baffling looks exceptional. The barrel internals are ridged, with a knife-edge baffle and a conical baffle behind that shielding the prisms. The objectives are fronted by lens rings with micro-ridged baffles. All this attention to detail may be by belt-and-braces in the era before computer ray-tracing. A modern Victory SF has apparently less baffling but stray light suppression every bit as good.

We know Dialyts boast Zeiss’ premium T* coatings from the engraving at the back of the bridge and they have the same unique dark pink hue that Zeiss bino’s have today, eschewing the greenish tobacco coatings that Leica, SW and others seem to have settled on. Even so, the coatings are less transparent than the modern equivalent (and this is a late pair), less transparent than Fujinon’s famous electron-beam coatings of the same era too.

Coatings of current 8x32 SF and 20-year-old Dialyt compared.

Dialyts have knife-edge and ridge baffles, conical prism shields to prevent stray light reaching the eye.

Optics - Eyepieces

Just like Zeiss’ modern-premium SFs, the objectives may be simple but the eyepieces are a complex design and to good effect.

Real-world eye relief is excellent, between 16mm and 18mm, depending on how far down you’re able to fold the eye cups! It’s enough to be really comfortable and to see most of the field with specs on. Blackouts seem exceptionally well controlled and false colour isn’t sensitive to eye position either, a fault that can plague older wide-field eyepieces (such as my Nikon’s 18x70s). Overall eyepiece comfort is superior to many current binoculars.

The other reason for a complex eyepiece is to give a wide field and for a 7x binocular these have it. At 8.6°, true field is the same as the model that replaced the Dialyts, the 7x42 Victory FL. It’s more than almost any other current 7x binocular (Nikon’s wild 7x50 WX excepted).

That high eye relief needs adjustable eye cups and these have old-fashioned folding rubber ones that mostly work fine, though the thick rubber tends to ‘rebound’ after folding, reducing the eye relief. Note that replacement eye cups are still available.

Accessories

The ClassiCs would originally have had a nice branded leather strap and a logoed leather soft case. However, you often see Dialyts sold with a modern Zeiss neoprene replacement strap which fits fine.

The eyepiece cap was a rectangular Zeiss-logoed one-piece item. You can still buy replacements at the time of writing.

In Use – Daytime

Ergonomics and Handling

The long Dialyts look front-heavy, but in fact they balance in the middle of the bridge, thanks to light objectives and a lack of internal focusing gubbins. That rearwards weight distribution helps make the Dialys comfy to hold for long periods, even with finger on focuser. But most likely you’ll grasp them around the barrels for extended viewing – something that feels natural and convenient. It’s a flexible comfortable hold.

In a back-to-the-future moment, much of the handling goodness of the Dialyts has been re-booted for the current Victory SF which also have a deliberately rearwards balance point and long barrels.

If the hold is comfy, so are the eyepieces. With plenty of eye relief, minimal blackouts and a wide field, eyepiece comfort doesn’t get better. Those tulip-shaped rubber cups look a bit primitive, but work well, extended or folded.

The focuser wheel is small and slim by modern standards, but perfectly usable with gloves. It’s generally super smooth, fluid and fast; but this pair has odd moments of heaviness and stiction that may just be age and wear. Still, what with the hugely deep field, following birds on the wing is extra easy.

Adjusting dioptre by twisting the right eyepiece is easy given the snappy optics. But I did notice that the dioptre varied a bit due to some rocking of the bridge. This may just be due to sticking and wear.

The View

Please be aware that these comments apply only to a late pair with T*P* coatings. Older Dialyts without those things won’t have such a good view.

The view basically just seems modern Alpha: bright, sharp, wide, full of contrast. It takes some side-by-side comparisons to realise that all those things are a little down on a pair of modern high-end Zeiss. To be completely fair to the Dialyts, this pair has some scratching to the eye lenses, but assume brightness at least will be a little down on a pair of SFs but much better than most older roofs with their lossy, pre-dielectric mirrors.

So it’s a great view, steady, comfortable and more immersive than many tunnel-view 7x bino’s (SW Habichts, I’m looking at you!). The low power makes it steady, too. But it’s the huge depth of field that make these such a user-friendly bino’ – as usual at 7x, everything from about 50m is perfectly in focus for me and usable even down to 20m. Focus on middle-distance, move your grip to the barrel ends and just enjoy! A deep field is an underrated advantage for watching birds on the wing.

Wide field 7x binoculars like these Dialyts are a real rarity. Consequently, the Dialyts have a more expansive, airier feel than, say, a pair of current Ultravid 7x42s HDs. This has an interesting consequence for me. I’m testing a pair of Fujinon 7x50 FMRT-SX alongside and although the Fujis are optically perhaps the best 7x bino’s ever made, I actually prefer the Dialyts due to that wider field. I prefer them to those modern Ultravids for the same reason.

Flat field?

No.

Alright, let’s break that terse statement down. The field seems wide and well corrected enough during day-to-day use, but in fact some blur creeps gradually into the last half and gets significant towards the very edge. A bit worse than a modern pair of Zeiss 8x42s, it’s a non-issue for me by day. I just like that wide field and am happy to pay the price with a soft edge. But for astronomy it’s more of a spoiler – see below.

Off axis blurring is gradual, but worse at the edge than most modern Zeiss.

Chromatic Aberration

Binoculars like the Dialyts with external focusing (i.e. no internal focusing lens) tend to exhibit lower levels of false colour, which is why it troubles porro-prism bino’s so much less than roofs. So, despite simple objectives with no HD glass (or I assume not!), the Dialyts have slightly lower false colour than a pair of modern Zeiss Conquest HDs and not much more than the 8x42 SFs with their ‘Ultra-FL’ lenses.

This a great feature and it gets better. The view does deteriorate off-axis, from blur caused by field curvature and some astigmatism, but not from any significant increase in false colour towards the field edge, unlike almost any current Zeiss model.

In everyday use, I just never really noticed false colour in the Dialyts: unusual for a binocular of this era.

In Use – Dusk

Dusk brightness is excellent – the Dialyts penetrate deep into shadows. Under the brightest dusk sky, I noticed only a touch of veiling flare, a result that equals the best current models (including Zeiss 8x42 SFs, which I’d tested under identical conditions days previously).

In Use – Observing the Night Sky

A distant bright security lamp generated no prism spikes or ghosts as it often does with other bino’s, just a flare of fine spikes all around. This effect was worse in the left barrel and was due to scatter by some internal coating deterioration and scratching on the eye lens.

Stars start to distort from field curvature and astigmatism from about 50% width, but in the last 1/3 or so faint stars become blurred into a mist and vanish. I’ll discuss this in more detail in the Deep Sky section below.

Brightness and reach are just a little below the standard of a pair of Leica 7x42 Ultravid HDs I tested recently, likely due to the less transmissive coatings from twenty years ago.

The Moon

I caught a 27-day-old Moon, the very thinnest of crescents, just before dawn and very low in a bright sky. I noticed it quite by accident, gazing out the kitchen window whilst making breakfast. Despite the lowest contrast, the Dialyts showed the nearly-new Moon to perfection – crisp and sharp with no false colour and even a trace of detail, despite the challenging circumstances.

Planets

Mars showed strong natural colour and no spikes or flare, whilst brilliant Jupiter – always a tough bino’ test - showed just minor spikes.

Deep Sky

The field is exceptionally wide and encompasses, for instance, both Betelgeuse and Bellatrix. However, then both stars are near the field-stop and are very distorted into long arced lines. But the whole Hyades fit without too much distortion of Aldebaran. Similarly, Orion’s sword and belt fit with room to spare, but Mintaka and Nair Al Saif suffer distortion a little worse than through modern Zeiss.

That distortion and extinction of stars towards the edge isn’t really distracting when you’re focusing on something centre field. So the Pleiades look nice and sparkling and well populated with pinpoint stars, surrounded by some context stars I’m vaguely aware of. It’s the same for Orion’s sword region. The nebula is small at this magnification, but its nicely misty-bright, the surrounding stars brilliant and pinpoint.

No, the problem comes with really rich star fields. Looking at the Double Cluster in Perseus, I’m aware that nearby Stock 2 is already in the extinction zone, many of its stars obliterated, ditto Trumpler 2 behind. The rich star field around the cluster pair is bordered by a ring of mist with just a few bright few stars, the rest stretched to oblivion. This effect spoils rich fields a little for me.

Otherwise, brighter DSOs and their surroundings are well picked out. I enjoy the characteristic shapes of the Beehive Cluster and M35, both resolved with direct vision. I can start to make out individual star dust in Auriga clusters the Pinwheel and the Starfish. I try to spot the Crab Nebula in Taurus; I think I spotted it with averted vision, but a check with my 18x70s leaves me less sure.

Astronomy performance is similar to a modern 7x42 like Leica’s Ultravid HDs, but with a wider field. The big downside is that for sweeping Milky Way star fields, off-axis aberrations are higher than I’d like.

Zeiss 7x42 Dialyt vs Fujinon 7x50 FMTR-SX

The Fujis are a traditional mil-spec ruggedised porro – ridiculously heavy and large for a 7x50. But famously they feature outstanding coatings, very high-quality optics and a field flattener. They are still available, but the pair I tested was from the era of the Dialyts. The Fujis were a little better in most ways – brighter, sharper, higher resolution – but they have 1.3° less true field and feel much more ‘closed in’. For this reason alone, I just much preferred the Dialyts.

Buying

Zeiss Dialyts are still readily available used. The problem is that even rough ones are now rarely cheap, but have a had a minimum of sixteen years’ wear. They can still be repaired by Zeiss, but parts are expensive and Zeiss have a reputation for replacing anything that’s slightly worn.

The upshot is that a service involving replacement of optical parts (eyepieces, objectives, prisms) could cost £400-£1000, net of shipping and duties. Given that you’ll have paid £500-800 for the bino’s in the first place, a pair of Dialyts could cost as much as a pair of 8x42 SFs! Caveat emptor and all that.

Summary

Among the cognoscenti, the 7x42 Dialyts are regarded as a Zeiss masterpiece. No dissent from me. The wide, sharp, deep and bright view is exceptional, much like a recent SF’s. False colour levels are very low without HD or Ultra-FL, presumably due to the external focusing.

So the optics are great, but the Dialyts are quite light and handle well too. Many current Alpha binoculars still have less perfect eyepiece comfort than this 1981 design. Even the focuser would be excellent, given a service.

Apart from lack of full-immersion waterproofing, the only less-than-modern feature is the field-edge curvature and astigmatism. It doesn’t matter by day (to me at least), but it makes them less attractive for sweeping star-fields than they could be.

Overall, though, I really loved the Dialyts and genuinely wish I’d kept my minty originals. Which brings me to the other problem ...

Existing Dialyts are getting old and expensively high-maintenance (much like yours truly). This pair were advertised as optically sound and initially seemed so, but close inspection over the course of this review sadly revealed otherwise.

The scruffy armour was expected and cheap to replace, but not the scratched eyepieces. Even the objectives had very minor radial scratching too. Worse, the prism coatings had deteriorated in the left barrel making it just a little misty. That deterioration needed urgent attention in case it was fungal. I researched a service, but if Zeiss had wanted to replace the entire optics (certainly possible) I could have faced a £1000 repair bill. I very reluctantly returned them. As I said at the start, caveat emptor.

Record players, tape decks, valve amps; electric bikes that look like Sixties mopeds. Leica’s Trinovid Classics. Retro is everywhere. So, come on Zeiss, how about a 7x42 Dialyt re-issue? I’d buy a pair ...

The Zeiss 7x42 Dialyts are a genuinely exceptional binocular, even today, and get my highest recommendation. Trouble is, you’ll be lucky to find a really good example and any optical repairs will be expensive. And make sure you buy T*P* for a modern view.