WALTER DIONI CANCÚN, MÉXICO
** Amalgamate, is a technical term indicating the fusion of two superimposed images, producing a synthesis of both images. To do this, an image that has background defects produced by shading due to dust or other impurities in the light system, is digitally merged (amalgamated) with a second picture taken from the same field of view having first withdrawn the object photographed.
For the procedure to be effective the last image must be subsequently inverted. Thus, in the third image (the correction screen) the dark spots of the background will be now represented by light spots of corresponding density. By merging digitally the original image and the correction screen image with clear spots, neutralises the corresponding dark spots of the first. Usually the result is spectacular, producing a much cleaner background than the original photo. Of course junk included into the preparation (not at the background) are not removed by this method.
The existence of this technique makes it sensible to routinely take an image of the background, by displacing the slide with the subject, before photographing interesting subjects. If you do not need it, it is easy to discard. But often to the more careful photographer will escape details that are discovered later. The technique also helps, and it is not a less important feature, to remove or conceal the existence of unwanted light gradients, many times present in images captured with the low power objectives.
function of an important utility, doesn't seem to be widely used by most microscopists.
Let me therefore briefly present here its application in Motic (as well as Photoshop
I often use this program because it is an integral part of the processing software of the DC-3 camera included in my microscope. A click on the appropriate icon opens the “amalgamation box”.
final image is almost always something light in tone and low in contrast, but the Autocorrect Tools of any image editor, or
simply the "gamma"
correction can retrieve a good image.
I detail the technique applicable with the Motic software so that anyone who wants to experiment with another image processor has an initial guide.
Photoshop and PhotoPaint
Both Photoshop and PhotoPaint have amalgamation software in their Images menu.
But offer many more options than the Motic, and the interested microscopist should try some (especially the “Superposition” commands, which in turn have options that offer various possibilities). In either program you should open simultaneously the already inverted “correction screen” image, and the image to correct.
Then open the menu IMAGES, and select Calculations, or Calculate, which opens the job options. Select first and second images in the dialog box, and apply Overlay. The degree of intensity of the overlay can be graduated, and this will depend on the photographed subject and the density of the “correction screen”. I got good results using 90 %.
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Published in the February 2010 edition of Micscape.
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