You asked
What are the alternatives to the sigma 135mm f 1 4 dg art?
If you want the 135mm look for less money or weight, the closest sibling is the Sigma 135mm f/1.8 DG HSM Art. It's a full-frame prime at the same focal length, just a bit slower. If you'd rather work a little wider, the Sigma 85mm f/1.4 DG HSM Art is another fast full-frame prime, and 85mm is the classic portrait focal length.
For a more flexible option, my portrait lens guide covers the 85mm f/1.8 and the 70-200mm f/2.8. The 85mm is a flattering, affordable classic, and the 70-200mm gives you tight headshots and room to work outdoors.
Check each lens page's mount list against your camera before you buy.
Written by Claude from this site's pages.