diff --git a/CDTools/datasets/ptycho_2d_dataset.py b/CDTools/datasets/ptycho_2d_dataset.py
index c5bc416..0902602 100644
--- a/CDTools/datasets/ptycho_2d_dataset.py
+++ b/CDTools/datasets/ptycho_2d_dataset.py
@@ -28,10 +28,12 @@ class Ptycho2DDataset(CDataset):
     def __init__(self, translations, patterns, axes=None, *args, **kwargs):
         """The __init__ function allows construction from python objects.
 
-
         The detector_geometry dictionary is defined to have the
         entries defined by the outputs of data.get_detector_geometry.
 
+        Note that the created dataset object will not copy the data in the
+        patterns parameter in order to avoid doubling the memory requiement
+        for large datasets.
 
         Parameters
         ----------
@@ -62,7 +64,11 @@ class Ptycho2DDataset(CDataset):
         super(Ptycho2DDataset,self).__init__(*args, **kwargs)
         self.axes = copy(axes)
         self.translations = t.tensor(translations, dtype=t.float32)
-        self.patterns = t.tensor(patterns, dtype=t.float32)
+        
+        self.patterns = t.as_tensor(patterns, dtype=t.float32)
+        if self.patterns.dtype == t.float64:
+            raise NotImplementedError('64-bit floats are not supported and precision will not be retained in reconstructions! Please explicitly convert your data to 32-bit or submit a pull request')
+
         if self.mask is None:
             self.mask = t.ones(self.patterns.shape[-2:]).to(dtype=t.bool)
         self.mask.masked_fill_(t.isnan(t.sum(self.patterns,dim=(0,))),0)
@@ -147,10 +153,13 @@ class Ptycho2DDataset(CDataset):
         # Load the data that is only relevant for this class
         patterns, axes = cdtdata.get_data(cxi_file)
         translations = cdtdata.get_ptycho_translations(cxi_file)
-
         # And now re-do the stuff from __init__
-        dataset.translations = t.Tensor(translations).clone()
-        dataset.patterns = t.Tensor(patterns).clone()
+        dataset.translations = t.tensor(translations, dtype=t.float32)
+
+        dataset.patterns = t.as_tensor(patterns)
+        if dataset.patterns.dtype == t.float64:
+            raise NotImplementedError('64-bit floats are not supported and precision will not be retained in reconstructions! Please explicitly convert your data to 32-bit or submit a pull request')
+
         dataset.axes = axes
         if dataset.mask is None:
             dataset.mask = t.ones(dataset.patterns.shape[-2:]).to(dtype=t.bool)
@@ -210,8 +219,21 @@ class Ptycho2DDataset(CDataset):
                 return meas_data * mask
 
         translations = self.translations.detach().cpu().numpy()
-        nanomap_values = (self.mask.to(t.float32) * self.patterns).sum(dim=(1,2)).detach().cpu().numpy()
+        
+        # This takes about twice as long as it would to just do it all at
+        # once, but it avoids creating another self.patterns-sized array
+        # as an intermediate step. This can be super important because
+        # self.patterns can be more than half the available memory
+        nanomap_values = np.ones(self.translations.shape[0])
 
+        chunk_size = 10
+        for i in range(0, self.translations.shape[0], chunk_size):
+            nanomap_values[i:i+chunk_size] = \
+                t.sum(self.mask * self.patterns[i:i+chunk_size],dim=(1,2))
+
+        # This is the faster but more memory-intensive version
+        # nanomap_values = (self.mask * self.patterns).sum(dim=(1,2)).detach().cpu().numpy()
+    
         if logarithmic:
             cbar_title='Log Base 10 of Diffraction Intensity'
         else:
diff --git a/CDTools/tools/data/data.py b/CDTools/tools/data/data.py
index 2462cbd..ea59ac3 100644
--- a/CDTools/tools/data/data.py
+++ b/CDTools/tools/data/data.py
@@ -317,7 +317,6 @@ def get_dark(cxi_file):
     return darks
 
 
-
 def get_data(cxi_file, cut_zeroes = True):
     """Returns an array with the full stack of detector data defined in the cxi file object
 
@@ -350,10 +349,12 @@ def get_data(cxi_file, cut_zeroes = True):
         pull_from = 'entry_1/instrument_1/detector_1/data'
     else:
         raise KeyError('Data is not defined within cxi file')
-    data = np.array(cxi_file[pull_from]).astype(np.float32)
 
+    data = cxi_file[pull_from][:]
+    
+    # Use maximum in-place to avoid allocating any more memory than is needed
     if cut_zeroes:
-        data[data < 0] = 0
+        np.maximum(data,0,data)
 
     if 'axes' in cxi_file[pull_from].attrs:
         try:
diff --git a/CDTools/tools/polarization/polarization.py b/CDTools/tools/polarization/polarization.py
index d8dbe06..dd5a58b 100644
--- a/CDTools/tools/polarization/polarization.py
+++ b/CDTools/tools/polarization/polarization.py
@@ -217,5 +217,5 @@ def apply_half_wave_plate(probe, fast_axis_angle):
 # print(exitw[:, 0, :, :])
 # print('y', exitw[:, 1, :, :])
 
-a = t.ones(2, 4)
-print(t.sum(a, dim=1).shape)
\ No newline at end of file
+#a = t.ones(2, 4)
+#print(t.sum(a, dim=1).shape)