andrea tasselli:
2" filters as commonly referred here aren't really 2" but more likely between 44-43.5 mm in clear diameter (and threaded to M48) and sometimes even less so most definitely will not fit all sensors and I am considering FF sensor only but medium format sensors are just over the corner...
BTW, 2" threaded filters were and are still used for large telephoto lens of a couple of generations ago, the latest generations go for smaller ones.
You’re right and really depends on the brand but that principle also goes for 36mm, 31mm, etc..
Filter wheels also take on them around 1.5-2mm (depending on the brand) of each side of the corners where the filters are sitting. So for a 36mm filter you’ll loose 3mm, some times 4mm, etc..
I still think the best approach are the 2”, but that’s not my wallet we are talking about.
The only sensors size that those filters can’t cover are the Medium Format ones, but that is the type of camera that most of us won’t use it in the daily basis.
I’ve stopped buying 1.25” filers, 31mm and 36mm the minute that I went with fast systems.
I still use my “old” cameras, the 4/3’s sensors size who can take 1.25” easily, but starting to change the filters for me was not only a solving problem to work with the Hyperstar and the Samyang 135, but also an investment for the future since the major brands of astronomy equipment tend to upper the sensor sizes.
Best regards to all,
Cesar
