Reprocessing Historical Images - II, Restoring images from antiquated and/or poor quality sources |
Reprocessing Historical Images - II, Restoring images from antiquated and/or poor quality sources |
Aug 29 2008, 03:34 PM
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Interplanetary Dumpster Diver Group: Admin Posts: 4405 Joined: 17-February 04 From: Powell, TN Member No.: 33 |
I figure that it is time for another thread like this. I still find it astonishing to see the versions of a lot of images that are reproduced over and over again. For example, this is the last mosaic of Triton taken before the close encounter began. The version on the Planetary Photojournal is on the left, my version on the right. Clearly, this image was produced as part of the "instant science" campaign. They did a superb job getting images to the public in a speedy manner, but they are extremely rough, since the team was busy running the spacecraft. However, it is this version that keeps being recycled. Worse, the version on the photojournal is clearly scanned from a printed copy, causing further degradation.
Here is a similar comparison, this time using Proteus (still 1989N-1 on the Planetary Photojournal!). This discussion started in the thread about Viking crescents but was getting off topic, so I thought I would start a new thread here. -------------------- |
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Sep 2 2008, 06:10 PM
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Member Group: Members Posts: 106 Joined: 26-September 05 Member No.: 508 |
Ted, let's take your Proteus image as an example, due to its low DN values and high noise ratio there is a mathematical limit to the information that this image can hold. When I look at the NASA version my brain realizes that this is a noisy picture and interprets it accordingly. When I look at your version which looks perfect and as if taken under ideal conditions, my brain interprets all the details as real and that is the problem. Not only the real craters, but also any chance alignment of light and dark pixels looks like real features.
Also some of the real information that our brains would have no difficulty seeing it from the noisy background is also lost in the softening process. Try removing noise from Cassini SAR images, you will not be able to see many of the fine details. This is a little bit like restoring historical artefacts to the limit that will make them look newly made. You will both lose information and add false information at the same time. Maybe you can make the noise removal only at the last stage of your processing workflow and display two versions. |
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