Multiple Lens Folding magnifiers
Multiple lens folding magnifiers are general purpose magnifiers. They typically have multiple lens which when used in combination provide various levels of magnification.
Use a multiple lens folding magnifier where flexibility of magnification over quality of image is wanted.
Each lens is designed to reproduce the best image when used by itself. As you add additional lenses to increase the magnification the glass of the lens added and the layer of air between the lenses distort the magnified image and bends each color of light passing through by a different amount.
Triplet loupes are designed to overcome this distortion of the image and colors by using 3 separate pieces of glass specifically chosen work together to correct the image and color and those individual lenses are bonded together to remove the air gap, making one solid lens.
Coddington's and doublet use two lenses bonded together to partially correct the image and the color rendition of the loupe.
Multiple lens folding magnifiers do not have a flat image from edge to edge nor do they reproduce true color.