<div class="conteneur">
    <div class="row">
      <div class="flex-item col-4">
        <div class="card">
          <img class="card-img" src="https://www.ibisc.univ-evry.fr/~dupont/2.jpg">
          <div class="card-body">flou artistique</div>
        </div>
      </div>
      <div class="flex-item col-4">
        <div class="card">
          <img class="card-img" src="https://www.ibisc.univ-evry.fr/~dupont/6.jpg">
          <div class="card-body">Masque d'alaska</div>
        </div>
      </div>
      <div class="flex-item col-4">
        <div class="card">
          <img class="card-img" src="https://www.ibisc.univ-evry.fr/~dupont/23.jpg">

          <div class="card-body">Tombe la neige</div>
        </div>
      </div>
      <div class="flex-item col-4">
        <div class="card">
          <img class="card-img" src="https://www.ibisc.univ-evry.fr/~dupont/3.jpg">

          <div class="card-body">Encre et collage</div>
        </div>
      </div>
    </div>
  </div>
  </div>

body{
   width: 60%;
   margin : auto;
  // background: #212529;
}

*, ::after, ::before {
    box-sizing: border-box;
}

.conteneur{   
    width: 100%;
    padding-right: 15px;
    padding-left: 15px;
    margin-right: auto;
    margin-left: auto;
      

}

.row { 
    display: flex;
    flex-wrap: wrap;
    margin-right: -15px;
    margin-left: -15px;

 
}
.flex-item {
    position: relative;
    width: 100%;
    min-height: 1px;
    padding-right: 15px;
    padding-left: 15px;
    background: white;
    
 
}

.col-4 {
    flex: 0 0 33.333333%;
    max-width: 33.333333%;
}

.card {
    position: relative;
    display: flex;
    flex-direction: column;
    min-width: 0;
    word-wrap: break-word;
    background-clip: border-box;
    border: 1px solid rgba(0,0,0,.125);
    border-radius: .25rem;
}

.card-body {
    flex: 1 1 auto;
    padding: 1.25rem;
}

.card-img {
    width: 100%;
    border-radius: 5px;
    
}
img {
    vertical-align: middle;
    border-style: none;
}