Focus Stacking With The 75Ard1

The Rodenstock 75mm f/4.0 Apo Rodagon D M1:1 (75ARD1) duplication lens is a pretty amazing piece of glass, and in normal use at apertures of f/8 or so achieves adequate depth of field at around 1:1 magnification to give an excellent result on Cents. But at this aperture the lens is limited by diffraction, so there is a resolution and sharpness penalty paid to get good depth of field. Luckily, the lens has superb flatness of field and sharpness even wide open at f/4, but unfortunately depth of field at this aperture is not adequate to produce good sharpness on the field of a Cent at the same time as the high points of the design features. Luckily there is software out there that allows you to stitch together several photos taken at different focal planes, allowing a composite photograph that is in perfect focus with optimum sharpness across a much wider depth of field than can be achieved with a single image. This focus stacking technique takes a bit of practice to get best results but I have found is worth the effort.

Here is a focus stack of 5 images of a 57-D Lincoln Cent taken with the 75ARD1 at f/4 to show the finished product of this technique:



Notice that while the rims, devices and fields are all in good focus using the focus stacking technique, the background is unfocused. This is due to the composite images all being done at f/4, so the background is never in focus on any of the images that focus on the coin. I certainly could have included a focused background image that would have then been included in the composite image, but I focused only on the coin, and actually like the unfocused look of the background.

For those who have been following my posts, this cent is different from the one I usually use to test different photographic techniques. I thought it might be time to give the rest of the coins from the same outstanding roll of 1957-D Lincoln Cents a chance at being photographed.