I think that Tract is just using a marketing term, in using Schott HT in its updated binoculars
name.
Zeiss has offered the Zeiss Terra ED for several years now, and it also has Schott extra low dispersion glass, as they use it in their specifications.
Schott is a sister company of Zeiss, and Zeiss makes no special mention of glass types in their higher end.
I would like to know if having Schott glass really means anything special.
Jerry
I am surprised that you of all people would suggest this Jerry, and I seriously doubt that you are correct. If you are, I will eat my hat!
If it was just marketing smoke and mirrors by Tract without physically using the actual product, then they would leave themselves wide open to prosecution for false advertising. This is something I would have thought you would know. I don't think they are that stoopid. They would actually be using some grade of Schott HT glass somewhere in the new Toric's optical train.
Schott HT glass is a range of glass that has special 'High Transmission' properties - specifically incrementally more transmission than other types in the cooler part of the spectrum, and it is a low inclusion glass. There are many products. You can read all about it in their catalogue.
On the contrary to what you have said, Zeiss does specify what glass types it uses. It uses 'FL' glass in the FL series and HT also. The HT uses 'HT' glass as well (they say lenses, and perhaps in part of the A-K prism too), and the SF uses an 'Ultra FL' glass system (multiple FL elements). Whilst they don't specify part numbers, or grades, based on their designs and performance, you could be reasonaby sure that each of those types was the top spec offered by Schott in each of those categories at the time.
The Terra ED is a different kettle of fish. It is a budget model. There are many grades of ED glass. It likely uses amongst the cheapest and lowest spec ED glass that it could justify using the 'ED' name for.
Don't get hung up on the name Schott, there are hundreds of grades and specifications of glass available in their Catalogue. Other makers such as Ohara, Hoya, etc also have many different grades of glass available - some of which may be equal or superior to Schott. It all depends on the exact specifications, and just as importantly where and how they are used in a particular optical design.
I hope this helps clear things up for you and our newer members.
Chosun :gh: