diff --git a/src/openflexure_microscope_server/things/camera/simulation.py b/src/openflexure_microscope_server/things/camera/simulation.py
index f723c669..f169558f 100644
--- a/src/openflexure_microscope_server/things/camera/simulation.py
+++ b/src/openflexure_microscope_server/things/camera/simulation.py
@@ -13,7 +13,7 @@ import logging
 import time
 from threading import Thread
 from types import TracebackType
-from typing import Literal, Optional, Self
+from typing import Literal, Optional, Self, overload
 
 import numpy as np
 from PIL import Image, ImageFilter
@@ -43,6 +43,26 @@ BG_COLOR = [220, 215, 217]
 # Random Number Generator
 RNG = np.random.default_rng()
 
+DOWNSAMPLE = 2
+
+
+@overload
+def _downsample_shape(shape: tuple[int, int]) -> tuple[int, int]: ...
+
+
+@overload
+def _downsample_shape(shape: tuple[int, int, int]) -> tuple[int, int, int]: ...
+
+
+def _downsample_shape(
+    shape: tuple[int, int] | tuple[int, int, int],
+) -> tuple[int, int] | tuple[int, int, int]:
+    if len(shape) == 2:
+        return (shape[0] // DOWNSAMPLE, shape[1] // DOWNSAMPLE)
+    if len(shape) == 3:
+        return (shape[0] // DOWNSAMPLE, shape[1] // DOWNSAMPLE, shape[2])
+    raise ValueError("A shape should be a 2 or 3 element tuple.")
+
 
 class SimulatedCamera(BaseCamera):
     """A Thing that simulates a camera for testing."""
@@ -75,11 +95,11 @@ class SimulatedCamera(BaseCamera):
         """
         super().__init__(thing_server_interface)
         self.shape = shape
-        self.glyph_shape = glyph_shape
-        self.canvas_shape = canvas_shape
-        self.sample_limits = (
-            canvas_shape[:2] if sample_limits is None else sample_limits
-        )
+        self.ds_shape = _downsample_shape(shape)
+        self.glyph_shape = _downsample_shape(glyph_shape)
+        self.canvas_shape = _downsample_shape(canvas_shape)
+        sample_limits = canvas_shape[:2] if sample_limits is None else sample_limits
+        self.sample_limits = _downsample_shape(sample_limits)
         self.frame_interval = frame_interval
         self._capture_thread: Optional[Thread] = None
         self._capture_enabled = False
@@ -108,6 +128,7 @@ class SimulatedCamera(BaseCamera):
     def generate_sprites(self) -> None:
         """Generate sprites to populate the image."""
         sprite_sizes = [10, 21, 36, 40, 50]
+        sprite_sizes = [s / DOWNSAMPLE for s in sprite_sizes]
         self.sprites = []
 
         channel_block = np.zeros(self.glyph_shape[0:2])
@@ -202,9 +223,13 @@ class SimulatedCamera(BaseCamera):
         :param pos: a 3-item tuple containing the x,y,z coordinates of the 'stage'
         """
         canvas_width, canvas_height, _ = self.canvas_shape
-        image_width, image_height, _ = self.shape
-        # Scale position by RATIO to get position in base image.
-        im_pos = tuple(x * ratio for x, ratio in zip(pos, RATIO, strict=True))
+        image_width, image_height, _ = self.ds_shape
+        im_pos = (
+            pos[0] * RATIO[0] / DOWNSAMPLE,
+            pos[1] * RATIO[1] / DOWNSAMPLE,
+            pos[2] * RATIO[2],
+        )
+
         top_left = (
             int(im_pos[0]) - image_width // 2 + self.sample_limits[0] // 2,
             int(im_pos[1]) - image_height // 2 + self.sample_limits[1] // 2,
@@ -213,23 +238,24 @@ class SimulatedCamera(BaseCamera):
         # canvas edge.
         x_indices = (np.arange(top_left[0], top_left[0] + image_width)) % canvas_width
         y_indices = (np.arange(top_left[1], top_left[1] + image_height)) % canvas_height
-        z_indices = np.arange(self.shape[2])
+        z_indices = np.arange(self.ds_shape[2])
         canvas = self.canvas if self._show_sample else self.blank_canvas
         # Use npx to make each 1d index list 3D
         focused_image = canvas[np.ix_(x_indices, y_indices, z_indices)]
 
         image = fast_pil_blur(focused_image, sigma=np.abs(im_pos[2]) / 5)
 
-        if image.shape != self.shape:
+        if image.shape != self.ds_shape:
             raise ValueError(
-                f"Image shape {image.shape} does not match intended shape {self.shape}"
+                f"Image shape {image.shape} does not match intended shape {self.ds_shape}"
             )
 
         # Add noise and convert to uint8
-        image += RNG.normal(scale=self.noise_level, size=self.shape).astype("int16")
+        image += RNG.normal(scale=self.noise_level, size=self.ds_shape).astype("int16")
         image[image < 0] = 0
         image[image > 255] = 255
-        return Image.fromarray(image.astype("uint8"))
+        image = Image.fromarray(image.astype("uint8"))
+        return image.resize((self.shape[1], self.shape[0]), Image.BILINEAR)
 
     def generate_frame(self) -> Image.Image:
         """Generate a frame with blobs based on the stage coordinates."""