diff --git a/s3/src/main/scala/geotrellis/spark/io/s3/S3GeoTiffRDD.scala b/s3/src/main/scala/geotrellis/spark/io/s3/S3GeoTiffRDD.scala
index 328ca4065d..945de2fa2a 100644
--- a/s3/src/main/scala/geotrellis/spark/io/s3/S3GeoTiffRDD.scala
+++ b/s3/src/main/scala/geotrellis/spark/io/s3/S3GeoTiffRDD.scala
@@ -22,7 +22,7 @@ import geotrellis.raster.io.geotiff.tags.TiffTags
 import geotrellis.spark._
 import geotrellis.spark.io.RasterReader
 import geotrellis.spark.io.s3.util.S3RangeReader
-import geotrellis.util.StreamingByteReader
+import geotrellis.util.{StreamingByteReader, LazyLogging}
 import geotrellis.vector._
 
 import org.apache.hadoop.conf.Configuration
@@ -36,7 +36,7 @@ import java.nio.ByteBuffer
 /**
  * The S3GeoTiffRDD object allows for the creation of whole or windowed RDD[(K, V)]s from files on S3.
  */
-object S3GeoTiffRDD {
+object S3GeoTiffRDD extends LazyLogging {
   final val GEOTIFF_TIME_TAG_DEFAULT = "TIFFTAG_DATETIME"
   final val GEOTIFF_TIME_FORMAT_DEFAULT = "yyyy:MM:dd HH:mm:ss"
 
@@ -51,7 +51,8 @@ object S3GeoTiffRDD {
     *                       May result in a one input GeoTiff being split amongst multiple records if it exceeds this size.
     *                       If no maximum tile size is specific, then each file file is read fully.
     * @param numPartitions  How many partitions Spark should create when it repartitions the data.
-    * @param partitionBytes Desired partition size in bytes, at least one item per partition will be assigned
+    * @param partitionBytes Desired partition size in bytes, at least one item per partition will be assigned.
+                            This option is incompatible with the maxTileSize option.
     * @param chunkSize      How many bytes should be read in at a time.
     * @param delimiter      Delimiter to use for S3 objet listings. See
     * @param getS3Client    A function to instantiate an S3Client. Must be serializable.
@@ -163,7 +164,19 @@ object S3GeoTiffRDD {
     val repartitioned =
       options.numPartitions match {
         case Some(p) => windows.repartition(p)
-        case None => windows
+        case None =>
+          options.partitionBytes match {
+            case Some(byteCount) =>
+              // Because we do not have cell type information, we cannot
+              // perform the necessary estimates for the partition bytes.
+              logger.warn(
+                s"${classOf[Options].getName}.partitionBytes set with maxTileSize, " +
+                 "cannot perform partitioning based on byte count. Option ignored. " +
+                 "Use numPartitions instead.")
+              windows
+            case None =>
+              windows
+          }
       }
 
     repartitioned.map { case (objectRequest: GetObjectRequest, pixelWindow: GridBounds) =>
diff --git a/s3/src/main/scala/geotrellis/spark/io/s3/S3InputFormat.scala b/s3/src/main/scala/geotrellis/spark/io/s3/S3InputFormat.scala
index aeb221fd58..95660d6da1 100644
--- a/s3/src/main/scala/geotrellis/spark/io/s3/S3InputFormat.scala
+++ b/s3/src/main/scala/geotrellis/spark/io/s3/S3InputFormat.scala
@@ -20,9 +20,9 @@ import geotrellis.proj4.CRS
 import geotrellis.spark.io.hadoop._
 import geotrellis.util.LazyLogging
 
-import com.amazonaws.services.s3.model.{ListObjectsRequest, ObjectListing}
 import com.amazonaws.auth._
 import com.amazonaws.regions._
+import com.amazonaws.services.s3.model.{ListObjectsRequest, ObjectListing, S3ObjectSummary}
 import org.apache.hadoop.conf.Configuration
 import org.apache.hadoop.mapreduce.{InputFormat, Job, JobContext}
 
@@ -103,6 +103,21 @@ abstract class S3InputFormat[K, V] extends InputFormat[K,V] with LazyLogging {
 
     var splits: Vector[S3InputSplit] = Vector(makeNewSplit)
 
+    val s3ObjectFilter: S3ObjectSummary => Boolean =
+      { obj =>
+        val key = obj.getKey
+
+        val isDir = key.endsWith("/")
+        val isTiff =
+          if (extensions.isEmpty)
+            true
+          else {
+            extensions.map(key.endsWith).reduce(_ || _)
+          }
+
+        !isDir && isTiff
+      }
+
     if (null == partitionCountConf) {
       // By default attempt to make partitions the same size
       val maxSplitBytes = if (null == partitionSizeConf) S3InputFormat.DEFAULT_PARTITION_BYTES else partitionSizeConf.toLong
@@ -125,15 +140,7 @@ abstract class S3InputFormat[K, V] extends InputFormat[K,V] with LazyLogging {
 
       s3client
         .listObjectsIterator(request)
-        .filter(!_.getKey.endsWith("/"))
-        .filter { obj =>
-          if (extensions.isEmpty)
-            true
-          else {
-            val key = obj.getKey
-            extensions.map(key.endsWith).reduce(_ || _)
-          }
-        }
+        .filter(s3ObjectFilter)
         .foreach { obj =>
           val objSize = obj.getSize
           val curSplit =
@@ -159,7 +166,7 @@ abstract class S3InputFormat[K, V] extends InputFormat[K,V] with LazyLogging {
       val keys =
         s3client
           .listObjectsIterator(request)
-          .filter(! _.getKey.endsWith("/"))
+          .filter(s3ObjectFilter)
           .toVector
 
       val groupCount = math.max(1, keys.length / partitionCount)