What lens term indicates a non-rotating, fixed front filter ring during focusing?
Asked 11/25/2020
2 views
2 answers
0
I have a Canon EOS RP and built a fairly heavy attachment that mounts to the lens filter threads. This works on my EF 85mm f/1.8 because the filter ring is fixed to the lens body. On my 35mm f/1.8 Macro, the front section with the filter threads moves during focusing, and the extra load causes problems.
What term should I look for in lens specs to indicate that the front filter ring does not move during focusing? Is this related to the lens being labeled "macro"?
Also, when shopping for a 35mm-ish lens, what feature or wording should I look for if I need the filter mount to stay fixed and not put stress on the focusing motor?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
5y ago
2 Answers
1
"Internal focusing" is the term for that and it is rather common. Certainly a lot more so than "internal zooming" which makes a lens bulkier for transport and thus is comparatively rare for large zoom ranges. Off the cuff I remember the Panasonic DMC-FZ50 as a superzoom camera with both internal focusing and zooming.
To have either action "internal", the position of the front lens group cannot significantly involved in the zooming or focusing action. Since macro lenses are focusing at very short distances (while having a much larger focusing range than a "normal" lens with additional closeup lens at the front would have), sacrificing space in front of a principal focusing group by adding a non-focusing group may be particularly unwanted, so they are a slightly more likely candidate for non-internal focusing.
Originally by user95069. Source · Licensed CC BY-SA 4.0
user95069
5y ago
0
Generated from our catalog & community — verify before relying on it.
The key term to look for is internal focusing. That means focusing happens by moving lens groups inside the lens, rather than moving the front section. A lens with internal focusing typically has a fixed, non-rotating front filter ring, which is what you want for a heavy attachment.
This behavior is not implied by macro alone. In fact, macro lenses often have large focus travel and may extend or move the front section during focusing, so “macro” does not guarantee a fixed front ring.
When shopping, look for specs or descriptions such as internal focusing or IF. Also check whether the front element or filter ring rotates or extends during focusing. If your attachment is heavy, a lens with a fixed front and internal focusing will be the safer choice.
Recommended products
UniqueBot
AI5y ago
Your Answer
Related Questions
Can reverse-mounting a lens on its filter thread damage it, and how heavy a lens is safe?
Can a 58mm UV filter touch or damage the front element on the Canon EF 100mm f/2.8 Macro USM?
How can I safely remove a stuck screw-on filter from a lens?
Are screw-on wide-angle and macro converter attachments safe to use on a kit lens, and how is the image quality?
Does a screw-on 2x close-up adapter change minimum focusing distance?