There is no hard and fast answer to this, lens specs and designs change all the time, as do the filter holder requirements. However, as a rough guide, using a simple holder setup with 2 filter slots, and no lens shade a DSLR (small chip) will go down to 10mm. A 35mm & Full chip DSLR will go down to 16mm. A medium format 645 & 6×6 will go down to 35mm. A medium format 6×7 will go down to 45mm. A larger format 5×4 camera will go down to 70 – 90mm.