Image too large in container

[chizzy]

HI, Hope all is good. Could someone help me please with an example I'm using to learn from. Its a slide show that works ok with images of 600 X 400 , but when i try to use an image of 1280 X 720 i cant get it to stay in the container and it takes over the screen. I've tried using object-fit cover, contain and altering the img dimension but still get the same results when i use a larger image. THe code below is what i thought was relevant for the container and the image Any help would be appreciated …thanks

img {
float:left;
width:auto;
height:300px
vertical-align: middle;
object-fit: cover;
}

/* Position the image container (needed to position the left and right arrows) */
.container {
width:auto;
position: relative;
height:600px;
}