Does 72 mm Filter Interfere with 120 S Infinity Focus?

[Daniel81]

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Does a 72 mm lens filter on the front of the APO S Summarit 120 lens interfere with full retraction of the lens to infinity focus in any way?

Why does the lens also have a larger diameter thread edge on the front end at all?

[djmay]

11 minutes ago, Daniel81 said:

Does a 72 mm lens filter on the front of the APO S Summarit 120 lens interfere with full retraction of the lens to infinity focus in any way?

Why does the lens also have a larger diameter thread edge on the front end at all?

A filter on the lens does not interfere with focus. If you use a filter system, such as Lee Filters, you will need a clear filter (or just a ring) on the lens so that it can focus at infinity.

[LeicaR10]

Daniel81,   Here is a direct quote from Red Dot Forum, written by David Farkas, owner of the Leica Store Miami and his explanation of the S 120 lens and filters.  You can also follow the link and article to near the end and read more there.  

"One final cautionary note is that the 120mm APO-Macro has a somewhat quirky filter design. First, in addition to the correct 72mm filter threading on the front of the lens, there is also an 82mm filter thread on the outer barrel. Because the lens is not internal focusing, the inner barrel moves inside the wider outer part at infinity and past it for closer focus. This causes two issues. If you want to use a 4″ filter holder, you will need to add a spacer ring in order to achieve infinity focus. I typically take a cheap no-name 72mm filter and knock out the glass. The other concern is that if you make the mistake of mounting an 82mm filter on the outer barrel and go to focus, you might end up with a bit a of mess, with the inner part smashing through the filter."  

https://www.reddotforum.com/content/2020/04/the-definitive-guide-to-leica-s-lenses/ 

Personally, I use the Cokin 72mm Extension Ring on my S120.  Hope this helps.  r/ Mark

[SaW]

Just use adapter rings (72 ->77 & 77->82mm). You can then use the same 82mm filters and lens caps than on the other S lenses (the adapter rings do not interfere with the inner barrel move). This is my solution since day 1 with the 120mm.