You asked
Is the voigtl nder portrait heliar 75mm f 1 8 hard to focus manually?
The site doesn't say how hard this lens is to focus by hand, so I can't give you a verdict on the feel. What it does tell you is that the Voigtländer Portrait Heliar 75mm f/1.8 is manual focus only, with no autofocus and no stabilisation, so you'll be focusing by eye every time. It's made for full frame and fits Sony E, Nikon Z and Canon RF.
At f/1.8 the depth of field is shallow, so a small focus error will show up clearly. For a broader look at portrait focal lengths, including the 85mm and 50mm options, see my Portraits page.
Written by Claude from this site's pages.