Hi there,

Unfortunately, there is no option for that. 

But if you are trying to reduce the size of the images on portfolio single pages, you can try using this custom CSS:

.port-format-item img {
    max-height: 150px;
    width: auto;
}
.port-format-item {
    display: inline-block;
    margin: 0 0.5% 1%;
}
.port-format-content {
    text-align: center;
}

Regards,
Paul