This high-dynamic-range composite was created by Mike Malaska, a frequent VMC site contributor, from the Mars Express VMC images taken 11 July 2009 and shows numerous volcanoes of the Tharsis bulge on Mars.
From left to right: Arsia Mons (with cloud), Pavonis Mons, Ascraeus Mons, Ceraunius Tholus (small dark dot), and Uranius Mons (see larger subtle patch to the right of Ceraunius Tholus). (Access a labeled zoom in Mike's Flickr site.) Compare this with the October 2008 image prepared by Bogdan Stancescu that also shows the Tharsis Montes. Thanks Mike, once again, for an excellent job!
Click on 'Full story' for more details on his work and processing method, plus to see the full-size image.
First - here's the full-size image:
And here are the details. Mike writes:
To make the HDR composite image, the Mars express VMC raw images were converted to RGB .png files using Gordan Ugarkovic's VMC2RGB.exe utility. Four images with differing exposure settings were then loaded into Photoshop to create a layer stack with the dimmest image at the bottom and brightest at the top. The selected images were:
The images were converted to 16-bit RGB mode. The images were then manually aligned with the lowest image on the stack. To make this easier, key surface features were used, in this case Ascraeus Mons and Cerauius Tholus. Control points were set at the dark sky, the brightest part of the limb, a midpoint in the plain, and at the bright cloud near Arsia Mons. The contrast levels for each image in the layer stack was set with a black point (dark sky) at [5,5,5] and the brightest limb point set at (210,190,150). Layer masks were added to each image in the stack. To make a layer mask, the brightest section of the image was selected by using the Magic Wand tool starting at the bright point (limb) with a wand tolerance set at 20. The selection was expanded 10 pixels, then filled in the layer mask with black ink using the Paintbucket. The entire mask was Gaussian blurred by 10 pixels. Next, the brush tool was used to manually add either black ink or white ink to the mask. The stroke was generally along the crescent with a large brush and low flow and opacity. The layer opacity was then adjusted for best blending. Layer masking was repeated in the layer stack starting from the lowest to the highest (brightest). In this case, the darkest member of the sequence (09_192_14.11.57_VMC_Img_No_30_rgb.png) was not used.
Following the masking, a global Levels and Curves layer was added, followed by a Hue/Saturation layer. The saturation was increased to about 40. Initial adjustments were made to the levels and curves layer. Next, a 'combine all' layer was converted to a Hi-Pass filter overlay (3.5 pixel value) with the blend mode set at 'Overlay.' The curves and levels were adjusted so that the resulting coloring and contrast approximated Ted Stryk's earlier Mars Express VMC composite image.
Finally, the combined image was created as a new layer and the clone stamp tool was used to remove the known camera artifacts. A layer mask and black background were added to clip out the areas lacking proper image overlap.
The steps of the process, including thumbnails of the original images and manually created layer masks, can be seen here. An image of the final layer stack in Photoshop can be seen here, along with control point location.