diff --git a/src/backend/api/routers/vision.py b/src/backend/api/routers/vision.py
index 45f1c7c..9dcfab3 100644
--- a/src/backend/api/routers/vision.py
+++ b/src/backend/api/routers/vision.py
@@ -40,14 +40,22 @@ _IMAGE_EXTENSIONS = {
     "image/png": "png",
     "image/gif": "gif",
     "image/webp": "webp",
+    "image/bmp": "bmp",          # #99
+    "image/x-ms-bmp": "bmp",     # #99
 }
 
+# #99: the Opto bench cameras save BMP and the worker decodes it (PIL), so the
+# vision routes accept it on top of files.py's list. files.py is untouched: its
+# attachments are served by extension and BMP is not meant to be shown there.
+_VISION_IMAGE_TYPES = ALLOWED_IMAGE_TYPES | {"image/bmp", "image/x-ms-bmp"}
+
 # Sniffed from the first bytes, independent of the declared Content-Type: a
 # text file uploaded as "image/png" passes the header check above and must
-# still be caught before it reaches the worker as a bare 500 (#15). BMP and
-# TIFF are included even though `_IMAGE_EXTENSIONS` does not accept them,
-# because PIL - and so the worker - can decode both; this check only refuses
-# what is not a real image at all, it does not narrow the allow-list above.
+# still be caught before it reaches the worker as a bare 500 (#15). TIFF is
+# included even though the allow-list does not accept it (PIL, and so the
+# worker, can decode it; browsers do not show it in the result); BMP is now
+# also allowed (#99). This check only refuses what is not a real image at all,
+# it does not narrow the allow-list above.
 _IMAGE_SIGNATURES: tuple[tuple[bytes, ...], ...] = (
     (b"\x89PNG\r\n\x1a\n",),         # PNG
     (b"\xff\xd8\xff",),              # JPEG
@@ -83,7 +91,7 @@ async def _read_image(image: UploadFile) -> bytes:
     is in hand - the same two-step convention `files.py::upload_file` already
     uses, reused rather than reinvented here.
     """
-    if image.content_type not in ALLOWED_IMAGE_TYPES:
+    if image.content_type not in _VISION_IMAGE_TYPES:  # #99
         raise HTTPException(
             status_code=status.HTTP_400_BAD_REQUEST,
             detail=f"File type {image.content_type} not allowed. Must be an image.",
diff --git a/src/backend/tests/test_vision_bmp.py b/src/backend/tests/test_vision_bmp.py
new file mode 100644
index 0000000..c780584
--- /dev/null
+++ b/src/backend/tests/test_vision_bmp.py
@@ -0,0 +1,109 @@
+"""#99: the vision routes accept BMP (the Opto bench cameras save it); TIFF and
+non-images stay refused. files.py (attachments) is not touched by this."""
+import io
+
+import pytest
+from PIL import Image
+from sqlalchemy import select
+
+from src.backend.config import settings
+from src.backend.models.orm.vision import VisionReferenceImage
+from src.backend.tests.conftest import auth_headers, create_test_recipe
+from src.backend.tests.test_vision_upload_limits import (  # noqa: F401 - fixtures
+    recipe_parts, redirect_uploads, worker_says,
+)
+
+
+def a_bmp() -> bytes:
+    buffer = io.BytesIO()
+    Image.new("L", (64, 64), color=0).save(buffer, format="BMP")
+    return buffer.getvalue()
+
+
+def a_tiff() -> bytes:
+    buffer = io.BytesIO()
+    Image.new("L", (64, 64), color=0).save(buffer, format="TIFF")
+    return buffer.getvalue()
+
+
+async def a_camera_task(db_session, user):
+    recipe = await create_test_recipe(db_session, user.id)
+    _, task, _ = await recipe_parts(db_session, recipe.id)
+    task.task_type = "camera_measure"
+    task.vision_json = {"schema_version": 1, "name": "p", "tools": []}
+    await db_session.commit()
+    return task
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("content_type", ["image/bmp", "image/x-ms-bmp"])
+async def test_preview_accepts_a_bmp(
+    client, db_session, maker_user, worker_says, content_type,
+):
+    task = await a_camera_task(db_session, maker_user)
+    worker_says({"t1.diameter": 10.0})
+
+    response = await client.post(
+        "/api/vision/preview",
+        headers=auth_headers(maker_user),
+        files={"image": ("p.bmp", a_bmp(), content_type)},
+        data={"task_id": str(task.id)},
+    )
+
+    assert response.status_code != 400, response.text
+    assert response.status_code != 422, response.text
+
+
+@pytest.mark.asyncio
+async def test_preview_still_rejects_a_tiff(
+    client, db_session, maker_user, worker_says,
+):
+    task = await a_camera_task(db_session, maker_user)
+    worker_says({"t1.diameter": 10.0})
+
+    response = await client.post(
+        "/api/vision/preview",
+        headers=auth_headers(maker_user),
+        files={"image": ("p.tif", a_tiff(), "image/tiff")},
+        data={"task_id": str(task.id)},
+    )
+
+    assert response.status_code == 400
+
+
+@pytest.mark.asyncio
+async def test_a_text_file_declared_bmp_is_refused_on_its_bytes(
+    client, db_session, maker_user, worker_says,
+):
+    task = await a_camera_task(db_session, maker_user)
+    worker_says({"t1.diameter": 10.0})
+
+    response = await client.post(
+        "/api/vision/preview",
+        headers=auth_headers(maker_user),
+        files={"image": ("p.bmp", b"i am not an image", "image/bmp")},
+        data={"task_id": str(task.id)},
+    )
+
+    assert response.status_code == 422
+
+
+@pytest.mark.asyncio
+async def test_reference_image_bmp_is_saved_with_the_bmp_extension(
+    client, db_session, maker_user,
+):
+    recipe = await create_test_recipe(db_session, maker_user.id)
+    _, task, _ = await recipe_parts(db_session, recipe.id)
+    await db_session.commit()
+
+    response = await client.post(
+        "/api/vision/reference-images",
+        headers=auth_headers(maker_user),
+        files={"image": ("p.bmp", a_bmp(), "image/x-ms-bmp")},
+        data={"task_id": str(task.id)},
+    )
+
+    assert response.status_code == 200, response.text
+    saved = (await db_session.execute(select(VisionReferenceImage))).scalars().one()
+    assert saved.path.endswith(".bmp")
+    assert (settings.upload_path / saved.path).exists()