Is the color true?

[rengelman]

I'm new to this discussion and I imagine this question has been asked before, but I rarely see the issue discussed. If a caption does not specifically say "false colors," should I assume that the beautiful painter-like colors in Hubble and similar photos of nebulae are "true" -- that is, if human eyes could actually look through the Hubble telescope and somehow gather the appropriate light -- would these be the colors we would actually see? If not, how are they generated? They are so esthetically beautiful that I can't help wondering if it is the cosmos itself or merely an astronomer's or technician's choice of colors that provides the artistry.

Bob E.

[S. Bilderback]

It would be the opposite; it will most likely be false color unless it says true color.
Many of the pictures are taken in wavelengths of energy not visible to the human eye, and/or many times a composite of everything from infrared to gamma rays. Many times the false-colors are exaggerated to show detail.

[astroton]

This VLT (Very Large Telescope) images show some of the same objects in yet other colours.

http://www.eso.org/outreach/gallery/vlt ... opvlt.html

[l3p3r]

A common technique is to take photos of one object in many different wavelengths, assign a colour to each wavelength and then blend all the different images together to create the stunning images we see so often on APOD

An example

[planetquinn]

I’ve wondered about the colors too. Our color sensors (cones) shut down at low light levels and we go grayscale. Does anyone know if large aperature lenses can let us see color at night?
About “true’ or “false” color: I think “color” is entirely a sensory rendering. You could say that everything is, but color seems especially so to me. It doesn’t strike me as “false” to select and compress a broader spectrum into a visible image. Similar to how insects sense UV in their eyes, and radio “telescopes” yield images. Our eyes evolved in water, and developed in response to wavelengths most abundant there--less than a full octave.
Looking at these broad-spectrum images reduced for our viewing equipment is like listening to Bach played on a kazoo over the telephone--and trying to imagine what Bach really sounds like.

[S. Bilderback]

The intensity and spectrum of the light being reflected can have a substantial determination on its perceived color. Color correction filters are used in most photography situations - a subjective artistic decision. The amazing human brain does this correction automatically (within limitations). Using single wavelength filers and a light meter, the proportions of spectral light changes greatly from indoor light to direct sun light, If you had a color wheel in front of you in ambient indoor light and walk outside into bright Sun light, you would not perceive any change to the colors, a spectral analysis would show a great difference in wavelength proportions. That's the long answer to your question, it depends on the low light source and the reflective properties of what you are looking at.

The reason it is false color is that it is not only a shift in wavelengths but also a change to the proportions of the varying wavelengths, it would be like turning up or down only the red controls on your computer monitor.

P.S. I've heard Bach pieces played on vintage instruments of the day, it is a much different sound than hearing the Boston Philharmonic Orchestra playing.

[harry]

Thank you astroton for the link

http://www.eso.org/outreach/gallery/vlt ... opvlt.html