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Fudging photographic evidence

Earth, Moon, and Jupiter as seen from the Mars Global Surveyor and Mars Orbiter Camera, here. But heavily adjusted from very thin data; see below.

-- Edward Tufte

Are the Mars images a hoax?

The page contains this note:

     A note about the coloring process: The MGS MOC high resolution camera only
     takes grayscale (black-and-white) images. To "colorize" the image, a Mariner
     10 Earth/Moon image taken in 1973 was used to color the MOC Earth and Moon
     picture, and a recent Cassini image acquired during its Jupiter flyby was
     used to color the MOC Jupiter picture. The procedure used was as follows: the
     Mariner 10 and Cassini color images were converted from 24-bit color to 8-bit
     color using a JPEG to GIF conversion program. These 8-bit color images were
     converted to 8-bit grayscale and an associated lookup table mapping each gray
     value of that image to a red-green-blue color triplet (RGB). Each color
     triplet was root-sum-squared (RSS), and sorted in increasing RSS value. These
     sorted lists were brightness-to-color maps for their respective images. Each
     brightness-to-color map was then used to convert the 8-bit grayscale MOC
     image to an 8-bit color image. This 8-bit color image was then converted to a
     24-bit color image. The color image was edited to return the background to
     black. Three separate color tables were used: one each for the Earth, Moon
     and Jupiter. Jupiter's Galilean Satellites were not colored.

The bottom of that page contains links to the unprocessed Earth/Moon and Jupiter images. This Earth/Moon picture was cut from that raw image and enlarged to 400%. The Earth appears to be less than 27 pixels in diameter. The Moon is the barely visible smudge at the bottom right corner.

-- David A. Nash (email)

Where's the Moon?

A friend wrote that he had to clean his monitor and darken the room to find the Moon. In this version I used Photoshop's "replace color" command to lighten the background and reveal the Moon.

-- David A. Nash (email)

Original vs published images

For direct comparison, here is what was photographed and what was published:

-- Edward Tufte

Messing with pixels

In enlarging the "what was photographed" images it appears that pixel interpolation was used to smooth out picture. There are a variety of interpolation methods (examples), each with advantages and disadvantages, but they all add extra shape and shade information that were not actually photographed. NASA also used interpolation in preparing the "published" images.

-- David A. Nash (email)

ET small multiples and vertical comparisons

This is also a lesson in small multiples and showing comparisons. And scrolling down to find OJ made it the most powerful wordless editorial I have seen.

-- David A. Nash (email)

Alternations to Mars photographs not mentioned in NASA public report

The main release of the photograph to the public shows only the constructed image and does not document any of the image manipulations:

-- Edward Tufte

Excellent report on image altering in scientific publication

See Nicholas Wade in The New York Times on image fudging:

-- ET

The Commissar Vanishes

It doesn't take high technology to alter photographs. The Soviets were masters of this technique, to further their political ends.

On the topic of the thread. Nearly all NASA photos gathered from space or with telescopes are altered for color. Much of this is due to the limitations of the charge-coupled device (CCD), which is usually a black and white device. To make it color, either filters are used (which discard information and energy) or split by prism to multiple CCDs with different response curves (expensive and heavier).

-- Paul Parashak (email)

Mars at 30X vertical

From Nature, an image with 30x vertical exaggeration:

Source: Baker, Victor R. 2005. Picturing a recently active Mars. Nature 434: 280-283.

Original image source: Head, J.W. et al. 2005. Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars. Nature 434: 346-351.

The same page from Nature, reduced to 3x vertical exaggeration with Adobe Illustrator:

Detail of reduced 3x text:

-- Edward Tufte

Political video ad

As Time magazine photoshopped a still picture of OJ Simpson to make him blacker, so a Clinton campaign video has altered Obama's appearance.

Looking at before and after evokes for me the steps in Final Cut Studio 2 (a film video editing program) necessary to rescale the face and make the skin tone darker. Obama's shirt remains bright white in both the original and the Clinton videos. All this suggests horizontal stretching, desaturation, and contrast adjustments.

-- Edward Tufte

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