I just received a dual lens coupler in the mail and threw this together (very quickly) for a test of the magnification. This is a little "too much" (most things I want to photograph are larger than 1mm) and it's really hard to get the image in focus while working so close to the object (and relying on manually raising/lowering the tripod).
Lumix G6
Primary lens: Lumix 45-200 @200mm f5.6
Secondary lens: Lumix 14-45 @14mm f3.5
I only started in photography a few weeks ago and these are the only two lenses I have. I think using the 14-45mm as the primary and maybe a 14mm prime as the secondary would give me a better scale to work with.
Photo of the space between two millimeter marks on a tape measure (not cropped).
Photo of the ad hoc workspace. I used an iphone turned sideways with the light turned on.