diff --git a/phototag/helpers.py b/phototag/helpers.py
index 84bbb15..41fb508 100644
--- a/phototag/helpers.py
+++ b/phototag/helpers.py
@@ -65,12 +65,12 @@ def get_temp_directory(directory: str, start: str = "temp", append_random: int =
     return temp
 
 
-def convert_to_bytes(display_size: str) -> int:
+def convert_to_bytes(size_string: str) -> int:
     """
     Converts the string representation of data into it's integer byte equivalent.
 
-    :param display_size: A string representation of data size, a integer followed by 1-2 letters indicating unit.
+    :param size_string: A string representation of data size, a integer followed by 1-2 letters indicating unit.
     :return: The number of bytes the given string is equivalent to.
     """
-    match = re.match(r"(\d+)\s*(\w{1,2})", display_size)
+    match = re.match(r"(\d+)\s*(\w{1,2})", size_string)
     return int(match.group(1)) * byte_magnitudes[match.group(2)]
diff --git a/phototag/process.py b/phototag/process.py
index 062f68a..39ce3bb 100644
--- a/phototag/process.py
+++ b/phototag/process.py
@@ -9,7 +9,7 @@ import logging
 import os
 import shutil
 from threading import Thread
-from typing import Tuple, AnyStr, Optional, List, Dict
+from typing import Tuple, AnyStr, Optional, List, Dict, Callable
 
 import imageio
 import iptcinfo3
@@ -18,7 +18,6 @@ from PIL import Image
 from google.cloud import vision
 
 from . import TEMP_PATH, INPUT_PATH, RAW_EXTS
-from .config import config
 from .xmp import XMPParser
 
 log = logging.getLogger("process")
@@ -29,7 +28,7 @@ class MasterFileProcessor(object):
     Controls FileProcessor objects in the context of threading according to configuration options.
     """
 
-    def __init__(self, files: List[str], image_count: int, buffer_size: int, single_override: bool):
+    def __init__(self, files: List[str], image_count: int, buffer_size: int, single_override: bool, client=None):
         """
         Initializes a MasterFileProcessor object.
 
@@ -40,9 +39,10 @@ class MasterFileProcessor(object):
         """
         self.files, self.image_count = files, image_count
         self.buffer_size, self.single_override = buffer_size, single_override
+        self.client = client if client is not None else vision.ImageAnnotatorClient()
 
         self.waiting: Dict[int, FileProcessor] = {}  # FileProcessors that are ready to process, but are not.
-        self.running: Dict[int, Tuple[FileProcessor, Thread]] = {}  #  FileProcessors that are currently being processed in threads.
+        self.running: Dict[int, Tuple[FileProcessor, Thread]] = {}  # FPs that are currently being processed in threads.
         self.finished: Dict[int, FileProcessor] = {}  # FileProcessors that have finished processing.
 
         processors = [FileProcessor(file) for file in files]
@@ -76,14 +76,44 @@ class MasterFileProcessor(object):
         """
         Starts FileProcessor threads, loading zero or more threads simultaneously based on configuration options.
         """
+        available: List[int] = list(self.waiting.keys())
+        # At least 1 FP in queue and # of
+        while len(available) > 0 and len(self.running) < self.image_count:
+            # check that the smallest FP can fit in the specified buffer
+            if self.total_size + self.waiting[available[0]].size <= self.buffer_size:
+                self._start(available[0])
+            else:
+                # Could not fit under limit, thus all the subsequent items in the queue will not either.
+                # Subsequent items will be added through the _finished() callback.
+                break
+
+        # Ensure that at least 1 is in queue with single_override enabled
+        if self.single_override and len(self.running) == 0:
+            self._start(available[0])
+
+    def _start(self, key: int) -> None:
+        """
+        Starts a new FileProcessor Thread, moving the FP and creating it's thread in the running dict.
+
+        :param key: The integer key representing the FileProcessor being added.
+        """
+        fp = self.waiting.pop(key)
+        thread = Thread(
+            target=fp.run, args=(self.client,), kwargs={'callback': lambda: self._finished(key)}
+        )
+        thread.start()
 
     def _finished(self, key: int) -> None:
         """
         Called when a FileProcessor's thread has finished.
 
-        :param int key: The FileProcessor's integer key in the running array.
+        :param int key: The FileProcessor's integer key in the running dict.
         """
-        pass
+        # Remove the FileProcessor and the Thread fom the running dict.
+        fp, thread = self.running.pop(key)
+        self.finished[key] = fp
+        # Load FileProcessors if possible
+        self.load()
 
     @property
     def total_active(self) -> int:
@@ -101,7 +131,7 @@ class MasterFileProcessor(object):
 
         :return: the total number of bytes the images in the buffer take up on the disk.
         """
-        return sum(processor.size for processor in self.running.values())
+        return sum(processor.size for processor, thread in self.running.values())
 
 
 class FileProcessor(object):
@@ -167,11 +197,12 @@ class FileProcessor(object):
         else:
             self._optimize(os.path.join(INPUT_PATH, self.file_name), copy=self.temp_file_path)
 
-    def run(self, client: vision.ImageAnnotatorClient) -> None:
+    def run(self, client: vision.ImageAnnotatorClient, callback: Callable = None) -> None:
         """
         Optimize, find labels for and tag the file.
 
         :param client: The ImageAnnotatorClient to be used for interacting with the Google Vision API.
+        :param callback: Utility kwarg used for threading purposes.
         """
 
         try:
@@ -224,6 +255,7 @@ class FileProcessor(object):
             raise
         finally:
             self._cleanup()
+            callback()
 
     def _cleanup(self) -> None:
         """