<div class="container">
  <div class="wrapper">
    <img src="https://www.dangeloweb.it/wp-content/uploads/2020/07/gradiente-radiale-effetto-vignetta.jpg">
  </div>

  <div class="wrapper">
    <div class="vignetta"></div>
    <img src="https://www.dangeloweb.it/wp-content/uploads/2020/07/gradiente-radiale-effetto-vignetta.jpg">
  </div>
</div>

.container {
  display:flex;
}
.wrapper {
  position:relative;
}
.vignetta {
  position:absolute;
  top:0;
  left:0;
  width:340px;
  height:100%;
  background-image:
    radial-gradient(
      ellipse,
      rgba(0,0,0,0) 30%,
      rgba(0,0,0,1) 
    );
}
img {
  width:340px;
  display:block;
}