Nebula photographs record light from real gas, dust and stars, but there is more than one way to make the image. A colour camera can record visible-light colour channels together. A monochrome camera can take separate exposures through broadband or narrowband filters, later combined into an image. Infrared observations need a mapping into visible colour if we are to view them on a screen.
What the filters record
Hubble’s filter system is one example, described by NASA: its filters are hardware admitting "a range of wavelengths (broadband filters) or very specific wavelengths (narrowband filters)" (how Hubble filters work), and each filter returns what it calls "a monochromatic (grayscale) image", with the hues chosen afterwards (the colour note on a Hubble release). Stand in front of most nebulae with the naked eye and you'd see a faint grey smudge, because at that light level you are seeing with rods rather than cones, and rods carry no colour information (NIH StatPearls, Physiology, Night Vision).
Where processing becomes interpretation
So these are real observations, processed to be readable, and where the processing ends and interpretation begins is a matter of degree rather than a hard line. Our nebula collection includes Webb NIRCam imagery in mapped colour on Pillars of Carina, and an AI illustration on Orion Cradle. The product pages distinguish those processes and give the applicable source credits; the wider catalogue sits under astronomy prints. If you want the object itself explained, we wrote what is a nebula.
Questions like this one live in Looking up next to the longer explainers. How people get pictures of galaxies covers the exposure side of the same problem, and what causes the aurora is the one light show you can photograph yourself.
Written by Craig Fearn, Aphelion Prints. Last updated .