I would export the two images to Photophsop as JPEG or TIFF files by using the picture feature of Imaris. Once in Photoshop you can superimpose the two images as two layers. This would let you play with the transparency of each layer and adjust contrast and gamma of the two layers separately. I don't see the advantage of doing this in Imaris, but you could try to convince the software that your two images are two optical sections in a confocal stack.

I would export the two images to Photophsop as JPEG or TIFF files by using the picture feature of Imaris. Once in Photoshop you can superimpose the two images as two layers. This would let you play with the transparency of each layer and adjust contrast and gamma of the two layers separately. I don't see the advantage of doing this in Imaris, but you could try to convince the software that your two images are two optical sections in a confocal stack.