diff --git a/src/main/java/org/janelia/colormipsearch/SparkMaskSearch.java b/src/main/java/org/janelia/colormipsearch/SparkMaskSearch.java
index 755e9b43..18a6d8d3 100644
--- a/src/main/java/org/janelia/colormipsearch/SparkMaskSearch.java
+++ b/src/main/java/org/janelia/colormipsearch/SparkMaskSearch.java
@@ -18,9 +18,13 @@
 
 import javax.imageio.ImageIO;
 import java.io.*;
+import java.nio.file.DirectoryStream;
 import java.nio.file.Files;
+import java.nio.file.Path;
 import java.nio.file.Paths;
+import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 import java.util.stream.Stream;
 
@@ -75,6 +79,16 @@ private ImagePlus readImagePlus(String filepath, String title, PortableDataStrea
         }
     }
 
+    private ImagePlus readImagePlus(String filepath, String title) throws Exception {
+        switch (getImageFormat(filepath)) {
+            case PNG:
+                return readPngToImagePlus(title, new FileInputStream(filepath));
+            case TIFF:
+                return readTiffToImagePlus(title, new FileInputStream(filepath));
+        }
+        throw new IllegalArgumentException("Image must be in PNG or TIFF format");
+    }
+
     private MaskSearchResult search(String filepath, ImagePlus image, ImagePlus mask, Integer maskThreshold) {
 
         try {
@@ -107,29 +121,38 @@ private MaskSearchResult search(String filepath, ImagePlus image, ImagePlus mask
      * Load an image archive into memory.
      * @param imagesFilepath
      */
-    public void loadImages(String imagesFilepath) {
+    public void loadImages(String imagesFilepath) throws IOException {
 
-        // We have to ensure each filepath ends with a wildcard, because it's very slow without.
-        // See https://issues.apache.org/jira/browse/SPARK-8437
-        StringBuffer filepaths = new StringBuffer();
+        List<String> paths = new ArrayList<>();
         for(String filepath : imagesFilepath.split(",")) {
-            if (!filepath.contains("*")) {
-                if (!filepath.endsWith("/")) {
-                    filepath += "/";
+            log.info("Loading image archive at: {}", filepath);
+            Path folder = Paths.get(filepath);
+            try (DirectoryStream<Path> stream = Files.newDirectoryStream(folder)) {
+                int c = 0;
+                for (Path entry : stream) {
+                    paths.add(entry.toString());
+                    c++;
                 }
-                filepath += "*";
+                log.info("  Read {} files", c);
             }
-            if (filepaths.length()>0) filepaths.append(",");
-            filepaths.append(filepath);
         }
 
-        log.info("Loading image archive at: {}", filepaths);
+        // Randomize path list so that each task has some paths from each directory. Otherwise, some tasks would only get
+        // files from an "easy" directory where all the files are small
+        Collections.shuffle(paths);
+
+        log.info("Total paths: {}", paths.size());
         log.info("Default parallelism: {}", context.defaultParallelism());
 
-        JavaPairRDD<String, PortableDataStream> filesRdd = context.binaryFiles(filepaths.toString());
-        log.info("filesRdd.numPartitions: {}", filesRdd.getNumPartitions());
+        // This is a lot faster than using binaryFiles because 1) the paths are shuffled, 2) we use an optimized
+        // directory listing stream which does not consider file sizes. As a bonus, it actually respects the parallelism
+        // setting, unlike binaryFiles which ignores it unless you set other arcane settings like openCostInByte.
+        JavaRDD<String> pathRDD = context.parallelize(paths);
+        log.info("filesRdd.numPartitions: {}", pathRDD.getNumPartitions());
 
-        this.imagePlusRDD = filesRdd.mapToPair(pair -> new Tuple2<>(pair._1, readImagePlus(pair._1, "search", pair._2))).cache();
+        // This RDD is cached so that it can be reused to search with multiple masks
+        this.imagePlusRDD = pathRDD.mapToPair(filepath ->
+                new Tuple2<>(filepath, readImagePlus(filepath, "search"))).cache();
 
         log.info("imagePlusRDD.numPartitions: {}", imagePlusRDD.getNumPartitions());
         log.info("imagePlusRDD.count: {}", imagePlusRDD.count());