DStretch Processing Information

 

 

Do you want to help identify possible historic signatures, enhance rock art, or just use your computer to experiment with this type of processing? All you need is a standard picture from your digital camera or even a scanned photo plus some special free software. You don't even need an expensive camera - a simple point & shoot digital camera with a built-in flash will work fine. But in a dusty cave like Sandia Cave, you need to take your photos after the dust has settled. On a heavily traveled weekend it may be impossible to obtain a dust-free photo (the tiny dust spheres reflect light back into your lens and cause the spots that show up in your picture).

{Ghost hunters have called these spots "orbs", and relate them to ghosts. but they can be minimized or even eliminated by using an off-camera flash that provides side or back light. But for DStretch processing often your on-camera flash (without dust) will provide the best exposure for this special color manipulation.}

 

This photo enhancement process is called DStretch or ImageJ which is an "applet" that can provide false color replacement in some instances which can help bring out certain features. The JAVA applet requires you to have Java script on your computer which is often updated. (The older version I was using to make the images below on a 64-bit Mac had a problem with long file names that I saved.) But the links above will guide you to the latest software version for your particular system.

The program has so many processing parameters that when you get a "good" result on your particular picture, be sure to "save as" a copy which usually adds some of the parameter initials to the saved file name which will help you duplicate your results on similar photos in the future. There is a bit of a learning process here so take careful notes on what works best for your photos.

The set of pictures below give a good example of the value of this process. In 2013 Mike Bilbo was using a "special light" in the cave to help him look for possible historic signatures. He thought he could see a hand print under some graffiti and took some photos which are processed below. Now the question is "was this a historic hand print, or a more recent print?"

This is the challenge for the archaeologist that is tasked with removing the graffiti without harming the historic material under the modern spray paint.

 

Original
lds or inv or ac
ybk
yds

 

Original
 
Processed
This is a good example of when processing can help identify possible historic marks on the graffiti covered walls. The paints in this example were obviously of a different type and the processing significantly enhanced the yellow color, which is similar to the ocher dust in the cave.

The yellow colors were also emphasized in this processed photo. However this photo shows numerous round dust spots reflecting the light on the right hand side of the photo.

Prior to the initial graffiti removal, the team will attempt to get wide angle photos of the cave walls, perhaps after an initial "dust wash" with a spray of pure water.

Click HERE to see additional processed photos

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