ART COPY 101
Fine Art Copy using the Better Light System and a few things from around your house.
by Ron Finley, Ron Finley Studios, Los Angeles
[This has been expanded a bit so that anyone who is a photographer but NOT a Better Light owner would be able to make some sense out of it, with the exception of refrences to the Zig Align.]

This is based on piece that I presented at our recent Better Light owner’s meeting on the topic of fine art reproduction. As I prepared to get up in front of a room full of people smarter than me, I thought I had better limit my talk about the ways we’ve found to use the Better Light Camera to copy even the most problematic paintings of any size. I’m neither a scientist nor optical designer, but a guy who’s made a living off photography for a lot of years and is as excited about it today as I was in college. The Better Light camera system has helped keep my fires going. In this section, "Art Copy Basics" I'm presenting a collection of art copy challenges, i.e. headaches, and how we deal with them.

Definitions (non-technical and slightly arbitrary):
Art Copy: For this discussion, we’re concerned with the full-sized (100%) high-definition direct digital reproduction of 2 dimensional (i.e. flat) including oil and acrylic paintings, watercolors, charcoal, pencil drawings, airbrush, collage, etc.
Glare: scattered light (non-coherent light) reflected by a rough or matte surface.
Specular reflection: coherent light reflected by a glossy, or mirrored surface.
Flare: the destructive, ugly halation/lens refraction caused by a specular reflection.
Highlight: the pleasing halation/lens refraction caused by a specular reflection.
The difference between a flare and a highlight? In Hollywood, it’s $2500 a day.

Lighting and the set-up:
For the purposes of discussion, we’ll assume that a pair of light banks are placed approximately 45 degrees to the plane of the art and roughly equidistant to it, and that the resultant light is uniform over a 4’ x 4’ area. We will also assume that the photographer has the skills (and preferably the owner of a Zig-Align cascading mirror system) to align both camera and painting so that the lens is both perpendicular to the painting and the film (sensor) plane of the camera.

Art Scan Challange #1: Scanning Heavily Varnished Canvases
While good for most art copy, this kind of lighting set-up referred to above can produce specular “fireworks” at the sides of glossy, paintings, particularly those with highly dimensional brush strokes, as impasto or palette knife. Many people, particularly those with vertical copy stands, partially beat this by using “cross-polarization” (polarizing acetate on the lights and a polarizer on the lens).This technique, in my opinion, is undesirable for several reasons. 1) It can affect the color of the painting , 2) it cuts down on the light available to the sensor by a huge amount (80% by my measurements), resulting in much lengthier scan times and even worse (according to Better Light Founder and designer Mike Collette), a noisier image, and 3) it greatly increases the amount of time a fragile work of art is exposed to the destructive effects of UV light. And then of course, there are those recalcitrant kicks that even cross-polarzation can’t kill.

A simpler approach, workspace allowing, can be achieved by using a longer focal length lens. Consider the typical “problem” painting below. This canvas acrylic paint is smooth, but is covered with a glossy varnish. (The square in the center is a blow-up of a section of the side of the painting). I shot this (with a full-frame SLR) without varying anything but the focal length of the lens. The approximate focal length equivalent of a 4/5 lens is in parenthesis.

One might ask if such a long lens having less-depth-of-field than a "normal" lens would require a higher f-stop to guarantee good focus. The answer, in a word, is no, since you are taking a photo of a flat object. A regular spherical lens used for 3-D photography achieves its most critical focus at a given object size (like a person) in an arc from the nodal point of the lens (picture a semi-circle of people). The wider the lens, the more severe the arc, the longer the lens, the flatter the arc, therefore the less “safety” stopping-down is required to achieve good focus across the entire field. Furthermore, if the lens has been specifically designed for copying flat artwork, the focus issue is even more moot, as these lenses have been ground same focus at the corners of the field as in the center. These “flat field” lenses were used throughout “process” photography before intermediate color separations and half-tones were done in a computer.

A note here on the nature of photographic lenses: other things being equal, the longer a focal length, the greater the circle of coverage. In any given lens “family” this increases proportionately to the focal length of the lens. For the Rodenstock APO Sironar N’s for example, at infinity, the 100mm lens has a circle of 150mm, the 210mm has a 315mm, the 300mm has a 450mm circle. Since the Better Light sensor area diagonal is only about 125mm, what is the benefit? For one thing, a larger lens circle offers an extended “sweet spot”, a non-technical term for that ultra-sharp section of the lens with minimal chromatic & spherical aberration and transmission fall-off. These evils occur more dramatically at the edges of the circle, especially in a wide-angle lens where the lens circle usually barely covers the format for which it’s marketed. I use a 360 Rodenstock APO RONAR, process lens which I find ideal. It is flat-field corrected, apochromatic, and optimized for flat art copy at large magnifications. It generates a very large circle (320mm at 1:1, more on the advantages of this in a moment) and there are no measurable transmission losses or color aberration issues across the entire field. The only downside with this lens is that the camera has to be approx. 20’ away to capture a 4’ tall image. Rodenstock ceased producing the APO Ronars in the late 1990’s as most of the “processes” they were designed for had become direct digital applications. Fortunately for Better Light owners, there are lots of these available usually on Ebay in the focal lengths 150mm, 240mm, 300mm, 360mm, & 480mm, and for very reasonable prices.