diff --git a/rtiow/src/output.rs b/rtiow/src/output.rs
index ccf9777..8c2f6af 100644
--- a/rtiow/src/output.rs
+++ b/rtiow/src/output.rs
@@ -1,5 +1,6 @@
 use std::collections::HashMap;
 use std::fs::File;
+use std::io::BufWriter;
 use std::path::Path;
 use std::sync::Arc;
 use std::sync::Mutex;
@@ -189,6 +190,7 @@ pub fn write_images<P: AsRef<Path>>(
         };
         info!("Saving {}", binary_path.to_string_lossy());
         let f = File::create(output_dir.join(binary_path))?;
+        let f = BufWriter::new(f);
         match it {
             ImageType::RGB01 => {
                 serde_json::ser::to_writer(
@@ -200,12 +202,12 @@ pub fn write_images<P: AsRef<Path>>(
                 )?;
             }
             ImageType::Grey01 | ImageType::GreyNormalized => {
-                // TODO(wathiede): make grey scale
                 serde_json::ser::to_writer(f, &img.pix.iter().map(|v| v.x).collect::<Vec<f32>>())?;
             }
         };
     }
     let f = File::create(output_dir.join("data.json"))?;
+    let f = BufWriter::new(f);
     serde_json::ser::to_writer(
         f,
         &Data {