Typo3 6.2 add a css class on a content element "image"

I add an image in the backend as content element. The type of this content element is "image". How can I add a css class to this img-tag?

I want something like this:

<img class="responsive" src="xyz.jpg"/>

Ho can I add a class on this image tag?

My approach:

temp.pics =CONTENT
temp.pics {
    table = tt_content
    select {
        selectFields = image
        pidInList.data = 52
        andWhere = colPos=3
    }
    innerWrap = class="responsive" |

}

My approach isn't really ready.