Canon RP

I built a somewhat heavy lens attachment that mounts to the filter ring. This is fine with my old 85mm f1.8 as the filter ring is directly on the lens body.

I recently got a 35mm f1.8 macro lens - here the filter ring is on the lens element that moves when focusing. As a result I cannot use my lens attachment (it struggles to move the element and causes a lens error.)


  • Is there term which denotes whether the filter ring moves during focusing? (Is this implied by the "macro" notation?)
  • Can you recommend for 35mm or thereabouts lens whose filter ring is fixed to the lens body? (Or at least does not stress the internal motor when focusing.)
  • 1
    \$\begingroup\$ Can you recommend for 35mm or thereabouts lens whose filter ring is fixed to the lens body? What mount? For Canon EF-S there is a 35mm macro \$\endgroup\$
    – xenoid
    Nov 26, 2020 at 7:38
  • \$\begingroup\$ You can use a polarizer filter where you remove the glass, inserted between the lens and the attachment. The lens will make the back ring turn but not the front. Of course these are not really meant to support the weight of you apparatus. \$\endgroup\$
    – xenoid
    Nov 26, 2020 at 7:41
  • \$\begingroup\$ This is an X→Y problem. The issue probably isn't whether the filter ring moves or not, it's probably whether the lens focuses using "focus-by-wire" or a mechanical connection when manually focusing. \$\endgroup\$
    – Michael C
    Nov 28, 2020 at 16:53

1 Answer 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.

  • \$\begingroup\$ Usually, internal focusing means the front of the lens doesn’t move in and out when focusing. To a first approximation the fronts of internal focusing also don’t rotate. But many lenses that don’t rotate the front when focusing are not internal focusing and change distance to subject when focusing. \$\endgroup\$ Nov 26, 2020 at 0:52

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