Used alone, the 200mm Micro-nikkor focuses down to only 1:1, the same as most other true macro lenses offered by Nikon, Canon, Sigma, and other lens manufacturers. But compared to a Nikon 105mm, the 200mm would require almost twice the working distance, the water between the front of the housing port and the subject. And too often this extra water distance would result in a less sharp image. The advantage of using this lens with T6 close-up lens is that the water distance is reduced to a workable 8-18" while the maximum magnification is increased to 1.8x life-size, a very significant increase over the1.0x of the lens alone. And does this while maintaining a maximum aperture of about f4 to f5.3 for focusing accuracy and viewfinder brightness.