.pic Merge 1.4 will now merge TIFF stacks generated by NIH-Image. However the images are inverted with respect to NIH-Image when merged. This is because NIH-Image designates white pixel values as 0 and black pixel values as 255: for many other programs (including .pic Merge) the reverse is true. To circumvent this problem, after doing all image enhancement in NIH-Image that you wish to perform (such as LUT enhancement etc) use the "invert" macro within the "Stacks" macro set and save the inverted version.