[X] My Assistant

[EDG]

This post by ugordan on my Ganymede mosaic intrigued me, and I just want to check something here.

It sounds like ugordan's software can just linearly interpolate between (say) a Green filter and a Violet filter image to create a (hopefully reasonably accurate) simulation of what a Blue filter image might look like - and then doing the same with other filters means that a simulated "true colour" image can be constructed.

e.g. (use http://pds-rings.seti.org/voyager/iss/inst...a1.html#filters as a reference). Let's say we had a Green filter image and a Violet filter image of Ganymede where a given pixel had a DN (data number, or 8-bit pixel brightness, from 0 to 255) of 69 in Green and 51 in Violet. Green peaks at 585 nm and Violet peaks at 400 nm, and we want to interpolate an image taken with a Blue filter which would peak at 480 nm. Blue is 80/185 of the way between the two (on the Violet side), which means that the DN of that pixel in Blue should be (69-51)*(80/185)=7.78, or 8 DN higher than the Violet DN, which is a DN of 59.

So if I create a program that can do that interpolation across the whole image, would the result be reasonably accurate simulation of an image actually taken with that filter ? That assumes of course that the surface responds linearly to visible light wavelengths, which isn't necessarily true. But then, I'm not wanting to do this for scientific analysis or anything - this is just for aesthetic purposes really, to try to construct simulated "true colour" images.

And could it be possible to extrapolate a reasonably realistic Red filter image by seeing the difference between (say) Green and Orange and extending that further (linearly) into the red?

Looking at this site it seems that the human eye's sensitivity peaks at 558, 531 and 419 nm for red, green and blue respectively, so (assuming this approach works) would interpolating to those wavelengths instead of the ones described in the ISS filter descriptions actually produce a result that is more like what the human eye would see rather than an eye tuned to Voyager's wavelengths?