I am using a 5D MKii and 50mm f1.8 stm. The issue is focusing and recomposing when using wide open aperture. I understand the reason of changing the focus plane, distance by moving the camera while recomposing, also the vey shallow depth of field and other factors. This topic has been debated since long (I have been searching Google and doing some reading) and several advice are on forums, blogs etc. 5DMkii being almost 10 yrs old the focusing system is not as advanced as other newer models, and its center focus point is only the most sensitive "cross type" and other focus point are not as accurate. Some people suggested to manually focus by using live view and zooming 5x or 10x then take the shot. Some suggested to avoid recomposing at all, etc. I am relatively new to portrait photography and still learning.
There are great examples of stunning portraits in this forum and I am sure some of our senior and portrait experts can give me some advice on how to minimize focus missing while recomposing using my existing gear. Please excuse my poor writing.
Looking forward to hear from you.