Can anyone tell me why the photos returned by the Mars Express look more like paintings/drawings than a photo?

Here is an example from todays (Jan 29) Astronomy Picture of the Day:

http://antwrp.gsfc.nasa.gov/apod/astropix.html

Also, the perspective of the above photo looks like it is taken very close to the ground looking sideways. How do they accomplish this? (I am guessing they point the camera at the horizon rather than straight down?) I am wondering why it looks like it is so close to the surface when it is 220 miles or so up, I guess it is perspective.

That particular image is computer generated view, from yet another computer generated image created from the original data. That's why they don't look like real images - because they aren't.

But even ones like this and this look more like paintings than the photographs they presumably are.

__________________
Everything I need to know I learned through Googling.

I've been wondering the same, and came up with the following possibilities:

a) stereo images combined on a small scale creating impression of more "depth"
b) postprocessing with some kind of embossing, again to give virtual impression of "depth" in 2d photos
c) result of the wider gamut of the input - The filters used are not regular RGB, but actually similar to those on the rovers (e.g. red filter extended to near-IR, and the other two filters also have deviations in that they record more than regular RGB filters). This added data might give the photos a peculier, non-standard look since the software will convert non-visible data to visible, presumably.

__________________
Quid quid latine dictum sit, altum viditur.

Look fine to me. Maybe we are not used to looking at colour images from Mars orbit.

Alternatively, the stereo component of the HRSC has much lower resolution than the multispectral part. This might cause some odd effects in composites.

Jon

No atmosphere on the horizon is the main problem. The daytime sky is solid black instead of the light blue that it really is. Or is it sorta reddish. How bout pinkish red?

__________________
Lighten up! This is a stellar board! Author: duh.

"The Sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do..." Author: Galileo supposedly.

At max resolution there does seem something strange about how the colours are constructed - patches of green and red rather than half tones. I assume this is a technical artefact. Any suggestions?

Jon

Can anyone tell me why the photos returned by the Mars Express look more like paintings/drawings than a photo?

I think the photos look like paintings because of the highly saturated colors. Load the images into an image editing program, reduce the saturation, and see if the photos then look more like orbital photos to you.

Thanks for the info!

I figured it had something to do with the post-processing, just wanted to get some other opinions.

Hmmm, One of the strange things about the Mars Express HRSC(High Resolution Stereo Camera) is that it is a linescanning camera where the CCD arrays are mounted in a way that makes each CCD image the surface for a different angle.

There are nine CCD lines in the HRSC I belive; IR, red(actually 750nm, so its similar to the L2(near IR) filters on the Spirit/Opportunity pancams), green, blue, the grayscale nadir channel(straight down), stereo 1 and 2 channels(one angled for +18,9 degrees and one for -18,9 degrees from the nadir channel, both grayscale), and two grayscale photometry channels(similar angling to the stereo channels). All CCDs have a resolution of a little over 5100 pixles and a FOV of 12 degrees, if i remember correctly, and can image 10m pr pixel... The instrument also has a 1024x1032 CCD for the Super Resolution Channel, that can image 2,3m pr pixel...

The stereo channels are grayscale, so they probably use the colour info from the R, G, and B channels to make colour maps for the software that renders the 3D images, and since the red, green and blue are not taken form the same angle, I guess they may have to do some recomputing of them to make one colour image from the top down viewpoint, so I guess they might just use the same software to render that too...

__________________
Game over, you lose, we hope you enjoyed playing the exciting game of Thermodynamics...