.image-container1 img {
    opacity: 0.5;/*通常は半透明*/
    transition: .3s;
  }
  
  .image-container1 img:hover {
    opacity: 1;/*ホバーで不透明*/
  }

  .image-container1{
    width:1200px;
    height:auto;
    position: relative;
}
.image-container1 img{
    width:100%;
    height:auto;
}
.overlay-text1 {
    position: absolute;
    top:50%;
    left:50%;
    transform: translate(-50%,-50%);
    padding:0;
    margin:0;
    font-size:30px;
    color: black;
}
.image-container1 :hover .overlay-text1{
    display: none;
}