Taking into account Lee’s comment from post #24:
i.e. “Joerg Schmidt has confirmed SF has HT glass but Zeiss are being coy about where exactly this is employed”
I did a bit of Googling . . .
The term ‘Schott HT glass’ (and ‘Shott HTultra glass’) doesn’t describe glass of a particular chemical composition,
but rather a total of 13 different glasses that have in common the highest transmittance values
See the 2 screen grabs from the Schott website:
https://www.us.schott.com/advanced_...ass/ht-and-htultra/index.html?us-origin=en-US
Also see the attached information sheet that indicates the glass is suitable for lenses or prisms (see ‘Supply Forms’)
- so Zeiss’ use verses Leica’s?
Zeiss may be understandably coy about mentioning HT glass in the SF model, since from a marketing viewpoint the primary claim of the HT model is its superior transmission
- both compared to the SF and other brands
And while the HT’s optical superiority is due to the totality of the technology it uses, since it’s named ‘HT’, it would be confusing as a marketing strategy to simultaneously:
- stress that the significant new optical technology it uses is HT glass, and
- then add . . . but so does the SF!
Of course for users this should not be a big issue. As with a sausage, you don't need to know the ingredients to enjoy the result
John