function be_attachment_field_credit( $form_fields, $post ) {

	    $form_fields['be-photographer-name'] = array(
	        'label' => 'Photographer Name',
	        'input' => 'text',
	        'value' => get_post_meta( $post->ID, 'be_photographer_name', true ),
	        'helps' => 'If provided, photo credit will be displayed',
	    );

	    $form_fields['be-photographer-url'] = array(
	        'label' => 'Photographer URL',
	        'input' => 'text',
	        'value' => get_post_meta( $post->ID, 'be_photographer_url', true ),
	        'helps' => 'Add Photographer URL',
	    );

	    return $form_fields;
	}

add_filter( 'attachment_fields_to_edit', 'be_attachment_field_credit', 10, 2 );

function be_attachment_field_credit_save( $post, $attachment ) {

	    if( isset( $attachment['be-photographer-name'] ) )
            update_post_meta( $post['ID'], 'be_photographer_name', $attachment['be-photographer-name'] );

        if( isset( $attachment['be-photographer-url'] ) )
	        update_post_meta( $post['ID'], 'be_photographer_url', esc_url( $attachment['be-photographer-url'] ) );

	    return $post;
	}

	add_filter( 'attachment_fields_to_save', 'be_attachment_field_credit_save', 10, 2 );