Index: src/wp-admin/css/edit.css
===================================================================
--- src/wp-admin/css/edit.css	(revision 47290)
+++ src/wp-admin/css/edit.css	(working copy)
@@ -1424,6 +1424,40 @@
 	}
 }
 
+/* one column on the attachment editor screen */
+@media only screen and (max-width: 1200px) {
+	.post-type-attachment .poststuff {
+		min-width: 0;
+	}
+
+	.post-type-attachment #wpbody-content .poststuff #post-body {
+		margin: 0;
+	}
+
+	.post-type-attachment #wpbody-content #post-body.columns-2 #postbox-container-1 {
+		margin-right: 0;
+		width: 100%;
+	}
+
+	.post-type-attachment .poststuff #postbox-container-1 .empty-container,
+	.post-type-attachment .poststuff #postbox-container-1 #side-sortables:empty {
+		border: 0 none;
+		height: 0;
+		min-height: 0;
+	}
+
+	.post-type-attachment .poststuff #post-body.columns-2 #side-sortables {
+		min-height: 0;
+		width: auto;
+	}
+
+	/* hide the radio buttons for column prefs */
+	.post-type-attachment .screen-layout,
+	.post-type-attachment .columns-prefs {
+		display: none;
+	}
+}
+
 /* one column on the post write/edit screen */
 @media only screen and (max-width: 850px) {
 	.poststuff {
Index: src/wp-admin/css/media.css
===================================================================
--- src/wp-admin/css/media.css	(revision 47290)
+++ src/wp-admin/css/media.css	(working copy)
@@ -852,6 +852,8 @@
 .wp_attachment_holder .imgedit-wrap .imgedit-panel-content {
 	float: left;
 	padding: 3px 16px 0 0;
+	min-width: 400px;
+	max-width: calc( 100% - 266px );
 }
 
 .wp_attachment_holder .imgedit-wrap .imgedit-settings {
@@ -1207,6 +1209,7 @@
 	.wp_attachment_holder .imgedit-wrap .imgedit-settings {
 		float: none;
 		width: auto;
+		max-width: none;
 	}
 }