<div class="container">
  <div class="box">
    <img src="https://source.unsplash.com/1000x800">
    <span>CSS</span>
  </div>
  <div class="box">
    <img src="https://source.unsplash.com/1000x802">
    <span>Image</span>
  </div>
  <div class="box">
    <img src="https://source.unsplash.com/1000x804">
    <span>Hover</span>
  </div>
  <div class="box">
    <img src="https://source.unsplash.com/1000x806">
    <span>Effect</span>
  </div>
</div>

.container {
  display: flex;
  width: 100%;
  padding: 4% 2%;
  box-sizing: border-box;
  height: 100vh;
}

.box {
  flex: 1;
  overflow: hidden;
  transition: .5s;
  margin: 0 2%;
  box-shadow: 0 20px 30px rgba(0,0,0,.1);
  line-height: 0;
}

.box > img {
  width: 200%;
  height: calc(100% - 10vh);
  object-fit: cover; 
  transition: .5s;
}

.box > span {
  font-size: 3.8vh;
  display: block;
  text-align: center;
  height: 10vh;
  line-height: 2.6;
}

.box:hover { flex: 1 1 50%; }
.box:hover > img {
  width: 100%;
  height: 100%;
}