I rummaged through my hard drives to find some old, illustrative examples, unfortunately all taken at my highly light-polluted home, Visual Limiting Magnitude around 3.5. Left image is from an unmodded Canon 1Ds. This camera, like the human eye, has very little sensitivity to the Deep Red Ha. Hence M42 comes out with a huge boost in Blue compared to captures by an astroCCD or even film, or modded DSLRs. This lack of sensitivity to Ha makes imaging M42 with an unmodded 1Ds a very noisy affair, since, basically, one is imaging the reflected wavelengths (like a Blue sky) and Teal OIII. Only rather heroic efforts at eking out the reluctant Reds ended up in the above rendition. But the Running Man comes through easily, presumably mostly a reflection nebula. Middle image shows what happened when I put a duo-tone Astronomik UHC in the optical path to the 1Ds. Since the Ha is hardly recorded at all, the overall nebula is shrunk to visible Reds and Teal OIII only. The Running Man is now non-existent. The right image used a modded Canon 20D and the Astronomik UHC (+UV/IR Blocker), a duo-tone combo that is quite narrowband compared to the Astronomik CLS (not used above). The UHC does a good job even with this much light pollution, on a modded DSLR(!) but forget reflection nebulae (the Running Man). Reflection nebulae will take many, many hours integration time if they are ever to show up in narrow duo-tone filters.