Innovative Technologies: ZEISS T* Coating

Confidence in the Thoughest Conditions

Science and innovative technologies, but primarily the close contact to passionate hunters lead to pioneering developments over and over again. This makes your “ZEISS” a reliable companion even under the toughest conditions.

Designed to withstand the forces of nature in extreme hunting and outdoor conditions, these high-performance optics also provide robustness and reliability expected by demanding users the world over. Electronics and additional innovative functions increasingly create new ways of experiencing nature and passion than never before.

T* coating – An outstanding feature of all ZEISS products

The historical invention of anti-reflective coatings by Professor Smakula is just a single event – an event that launched an entirely new epoch in the field of optics. Image brightness, twilight performance, and brilliance were redefined by the T* coating and are still an outstanding feature of all ZEISS products.

The difference lies in the transmission

Although a high-quality branded 8 x 56 pair of binoculars and any simple 8 x 56 pair have the same exit pupil, the stand hunter will notice a major difference at dawn and twilight. The difference lies in the transmission. This value indicates the percent of incidental light that exits through the eyepiece again. The different impact of exit pupil and transmission on image brightness can be illustrated as follows: the exit pupil refers to the size of the window from which light exits the binoculars. On good branded or cheap binoculars having the same data, this window is generally the same. The transmission value, however, identifies the transparency of this window. Is it clear and bright or cloudy and dark?

First-rate binoculars and riflescopes provide transmission values over 90%; measurements on the ZEISS Victory HT 8×54 showed a value of more than 95%. In practice, differences of 1 to 2% are unnoticeable. A 5% increase, however, provides decisive reserves in dwindling light and enables considerably longer observation and reliable aiming.

  • Standard Glass
  • SCHOTT HT Glass

Around the world, binoculars and riflescopes from ZEISS are considered the most powerful in their market and are preferred for use in difficult lighting situations. This is closely linked to the term T* coating which has become synonymous with maximum light intensity and brightest images.

Reflections on glass surfaces

In general, a variety of factors always results in a loss of light in optical devices. Reflections and antireflective coatings on the glass surfaces have the greatest impact because a small portion of light is reflected every time the light passes from air to glass (and vice versa). Without an effective coating, this would be 4% for each glass surface; over 6% on elaborate binoculars with large refractive indexes. High-quality ZEISS binoculars include up to 12 lens elements on each side plus two prisms. Depending on the number of cemented elements, 16 to 20 glass-air surfaces may be used. Without an effective coating, the transmission would be considerably less than 50%; the images would show low contrast and be dull.

T* multi-coating

Initial tests were conducted at Carl Zeiss Jena (patent allowed in 1935) and resulted in a method of applying a transmission coating to glass. At that time the T coating – a single coat – was born. It was replaced by the T* multi-coating at the end of the 1970s. The current, constantly enhanced and unique ZEISS T* multi-coating on all glass-air surfaces is not simply a fixed recipe but also an innovative multi-coat procedure with a typical six-coat structure that is individually matched to the single lens elements and glass materials. More than 100 layers evaporated in high vacuum on each side of the binoculars are, therefore, a common sight on ZEISS binoculars.

Twilight adjustment

The T* coating accounts for the increased blue sensitivity of the eye in deep twilight and further optimizes light efficiency when required the most.

The patent of Carl Zeiss for the invention of the coating of glass surfaces. Image: © ZEISS Archiv

Effect of the prisms

In addition to increasing transmission, the coating also serves as an effective, hard surface sealant that protects the partly sensitive optical glass. In addition to reflections the type of prism system plays a key role in image brightness on all binoculars. Therefore, all twilightcapable roof prisms of Carl Zeiss use the outstanding Abbe-König prism system. Although it is somewhat larger and heavier it does not need a light-swallowing mirror coating like the standard Schmidt-Pechan system. All light deflections inside the prisms take place as total reflections that, unlike a mirror, do not show a loss of light. This applies to Porro prisms as well, which also provide a very good foundation regarding image brightness.

Measurement

Transmission determining is relatively difficult, which is why the values rarely appear in test reports. The transmission values for spectral colors (different wavelengths) are determined individually by means of nearly 500 measurements. The result is assessed with the sensitivity of the human eye regarding colors (sensitivity curve). The eye is most sensitive to the green spectral range. Accordingly, these colors have the greatest influence. High infrared or UV transmission, on the other hand, is not included in the assessment because it is not perceived by the eye. The final result is a value known as day transmission.

Day and night transmission

While the cones in the retina are responsible for daytime vision primarily, it is the rods that take over at night or in very low light.

This results in a different sensitivity curve regarding colors: the maximum sensitivity moves to the blue spectrum. If the measured spectral transmission curve is assessed using this night sensitivity now it provides the night transmission. Night or day makes no difference to the binoculars but to the sensitivity of the eye.

Choosing the right Hunting Optics

The Perfect Companion

The most important factors when choosing your scope are your particular hunting preferences and the conditions in which you hunt. All-rounder or specialist – this crucial decision will depend not only on what scopes you already have, but also on what, where and how you will want to hunt in future.

  • If you will be hunting in daylight, what you need most is flexibility when it comes to magnification. The key aspects to consider are the terrain (flat country, mountains) and the type of hunting (hide, stalking).
  • Riflescopes with excellent optical performance are the number one choice if you will be hunting at twilight or by moonlight.
  • Reliable aiming, fast reactions and short distances: when on driven hunts, sights with a large field of view and low magnification allow you to aim with both eyes, thus increasing the reliability of your shot.
  • Various types of game and hunting, different times of day or environments: all-rounders with excellent optical clarity and a wide zoom range really come into their own here.
  • For high-precision shots over long distances, long-range scopes with extreme magnification and pinpoint ballistic settings are what you need.
  • If you are hunting in the mountains, it is important to have the flexibility to take long-distance shots, as well as to adjust your ballistic settings to suit the game. A product such as the ZEISS Victory Rangefinder System can be a great help here too.

Do you need more advice in your quest to find the perfect scope? Then visit our digital product advisor.

Finding the perfect binoculars

Good binoculars are like a loyal companion.

For the most part, hunting is not about the hunt itself; it is about being able to experience nature and, in particular, to view the game.

What constitutes the right binoculars will depend on the type of hunt, time of day and, last but not least, the hunter and their requirements. When hunting on the move, factors such as size, weight and ease of use are really important, on top of the optical considerations.

  • If you are hunting game that is on the move, you often have to act fast. Compact, lightweight binoculars that are really easy to use would be ideal here.
  • During the day, what hunters need most is to have a good overview through a wide field of view, along with good magnification, so they can aim at game properly.
  • In poor light, when hunting at night or at twilight, a good pair of binoculars with large lenses and good light transmission will allow hunters to get the most out of their hunt.
  • In order to measure distances accurately for an exact shot, the binoculars will need to offer enhanced technological features that are easy to use, on top of the optics themselves.
  • A built-in image stabilisation function will enable you to see clearly over extremely long distances – even without a tripod.

Do you need more advice in your quest to find the perfect binoculars? Then visit our digital product advisor.

Every detail at a glance – choosing the perfect spotting scope

Whether used to view game or simply see nature in a different way: spotting scopes give hunters and nature-lovers a unique perspective and enable them to take precise aim. Spotting scopes are usually needed to take accurate images over long distances, but sometimes they serve to pick up details on smaller animals that are already visible to the naked eye. So why do I need a spotting scope?

When deciding whether you need a spotting scope, as well as the performance data of the optics in question, such as maximum magnification, zoom range or field of view, it is recommended that you consider other factors too: for example, weight, dimensions, setting options, handling or ability to extend the product with corresponding accessories.

  • If used for aiming at game, the mobility of the spotting scope is important, as well as its optical performance: it should be lightweight, compact, robust and with no bells or whistles.
  • If used for viewing game, simple handling and maximum optical performance are the order of the day.
  • If used for identifying animals, when it is all about extreme magnification, a wide field of view and true-colour reproduction, every tiny detail counts.
  • Whether it will be connected to a camera or used for digiscoping – with the right spotting scope, you can record your sightings as photographs or moving images.

Do you need more advice in your quest to find the right spotting scope? Then visit our digital product advisor.