Apollo Discussions > The Reality of Apollo
Lunar Regolith Color Differences
BDL:
So I bought the book Apollo to The Moon which is by National Geographic and Smithsonian Institute of Air and Space and on the cover of the book a panorama taken by Charlie Duke of Descartes Highland. In it is John Young next to the Lunar Rover and the Lunar Module.
But what caught my eye was the unusually bright color of the regolith around it. The ground is noticeably brighter in color than photos, for example, of Buzz Aldrin in Tranquility Base.
Here’s the specific Apollo 16 panorama I’m referring to:
https://www.lpi.usra.edu/resources/apollopanoramas/pans/?pan=JSC2007e045380&zoom=True
Here’s the Apollo 11 photo I’m referring to: https://www.google.com/search?q=Buzz+Aldrin&client=safari&hl=en-ki&prmd=niv&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiBwbaK8LbfAhVLHDQIHU7-B4sQ_AUoAnoECA4QAg&biw=414&bih=617#imgrc=OrCtFTAR4v9ESM&imgdii=bLvkDKbPq2WEHM
Is the difference brightness due simple to different locations? Or was it the result of cameras?
bknight:
I'm definitely not a camera guy, but would it happen to be the way the camera is facing the sun? If you look at the foreground the regolith looks very much like the panorama, at least to me.
BDL:
--- Quote from: bknight on December 23, 2018, 05:49:24 PM ---I'm definitely not a camera guy, but would it happen to be the way the camera is facing the sun? If you look at the foreground the regolith looks very much like the panorama, at least to me.
--- End quote ---
Makes sense. Presuming the Apollo 16 mission took place at a different time on the lunar day, it’s possible that the sun had lit the regolith in just the way that would make it seem so bright.
onebigmonkey:
The Apollo 16 pan was done during the 3rd EVA, so conditions were definitely a lot brighter than for Apollo 11.
Kiwi:
--- Quote from: BDL on December 23, 2018, 04:19:46 PM ---Is the difference brightness due simple to different locations? Or was it the result of cameras?
--- End quote ---
In cases like this there are often multiple factors at work in earthbound photos: Camera, film, filter or glass in front of lens, exposure, location, angle of the sun to the ground, angle of camera to the sun, and photographer. Then there are processing factors - how the person making the finished photograph wanted it to look and the methods and materials used
By using a program called HTMLcolor to analyse the panorama, I found that whoever processed it must have deliberately made the greys as neutral as possible, because to my surprise, many of them were of exactly the same number in all three RBG values (red, blue, green).
But all the same, it was roughly over three times brighter in the down-sun portion (219, 219, 219) at the ends, than in a fairly bare part of the ground in the up-sun view (185, 185, 184) below the rover's right-hand wheel. If you didn't notice that difference, check again. It's easy for our brain to kid us that it's the same brightness everywhere in the panorama.
The astronauts generally used three different apertures for shooting panoramas. The smallest for down-sun, largest for up-sun (four times the exposure as down-sun), and in-between for the two right angles to the sun (twice down-sun).
Google lunar "lunar regolith colour/color" because right from Apollo 8 onward there were many discussions of the subject and later much controversy from hoaxland because many of the critics have never analysed their own photos or deliberately photographed a plot of ground or a piece of neutral grey carpet with a great variety of all the factors listed above.
Also look at many more photos of the moon. For instance, in the few very distant photos of the LM we can see the effect that the descent engine had in lightening the ground nearby by blowing away the topmost layer of soil. Keep in mind that in an up-sun view you are seeing a lot of shadow and in a down-sun view a lot less. That can give an illusion of darker soil when it's actually just much more shadow. It's also why we often see a "halo" around the shadow of the astronaut's chest in panoramas - almost no ground shadows at all.
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