Abstract: A double-ring lens filter holder includes a limiting ring, a lock ring, a fixed filter, an adjusting ring, a rotary filter, a compression ring, and at least one guide rod. Each guide rod is mounted through a respective curved recess which is formed through the limiting ring, and each guide rod is mounted securely on the rotary filter. When the fixed filter and the rotary filter are both polarizing filters, in addition to moving the guide rod to adjust the polarizing and darkening effects, the curved recess can also limit the rotating angle of the guide rod to eliminate the cross pattern. Besides, the protruding guide rod allows the users to accurately find the position at which the rotary filter can be rotated.

Abstract: An easily assembled filter adaptor assembly has a front mounting ring, a holding ring, a rear mounting ring, multiple intermediate rings, and at least one inner mounting ring, which are detachably connected with each other. Filters are selectively held between the front mounting ring, the holding ring, the intermediate rings, and the at least one inner mounting ring. The filter adaptor assembly has a simplified and compact structure. Accordingly, volume of the filter adaptor assembly can be reduced. Furthermore, numbers of the intermediate ring and the inner mounting ring can be increased or decreased so as to adjust numbers of the filters that can be assembled in the filter adaptor assembly.