SHADOW-FREE MOTH (& BUTTERFLY) IMAGES

Tony Thomas, mothman@nbnet.nb.ca

 You are visitor number   since 16 December 2003 

Copyright Tony Thomas 2003

Tony Thomas asserts his moral rights to be identified as the author of this work, including text and images.

Also see the settup used by Cliff Ferris

Goal

Many otherwise good images of spread moths are spoilt by unsightly shadows (an admittedly personal bias) especially when 2 light sources are used and each lamp is at a 45 degree angle to the moth. 4 or more lights will usually eliminate most of the shadows. Mounting a spread moth on a glass sheet by inserting the pin into a small piece of modelling clay and then illuminating the glass from below will remove the shadows created by 2 lights above the moth. However, this method severely degrades the image; the moth looks as though it has become greasy. A simple method to eliminate shadows is to photograph the moth against a black background, but finding a non-reflective pure flat black background is not easy (black velvet is often recommended) and a black background is not always desirable.

I describe the method I use to get shadow-free images using 2 lamps. A listing of components, the rationale for choosing them and alternatives are given in an appendix.

2 Basic Needs + 1

The two basic needs are to have i) a large diffuse light source, and ii) the moth at a significant distance from the background so that the illumination can get behind the spread moth and eliminate any shadow. A third need is strictly personal. I like to work in a vertical position so that I can look directly through the camera eyepiece without bending my neck. This dictates that the light-box needs to be vertical rather than in the more usual horizontal plane. However, this latter need has been solved by a few manufacturers whose digital cameras have monitors or lenses that swivel.

i) Large Diffuse Light Source

I meet this requirement by the use of 2 daylight compact fluorescent bulbs, each with a built-in reflector and each of which gives a beam spread of 80 degrees (Fig. 1 ).

Fig.1. Some components for shadow-free lighting showing just 1 of the 2 lamps.

Each bulb is housed in a gooseneck lamp that is positioned at the edge of a white plastic funnel of top diameter 16 inch, bottom diam. 4 inch and depth 10 inch. The funnel is attached to a 1/4 inch plywood sheet that I clamp to a L-shaped board that supports the funnel such that the top opening is vertical (Fig.1). I have not yet got around to making a permanent supporting base!

ii) Moth-holder, Background Distance

The moth-holder is a 9 inch long disposable glass pipet (Fig. 2) with an internal diameter of about 1mm at its narrow tip.

Fig. 2. Moth-holder. This styrofoam block is for illustration only, the actual block is a 4-inch diameter disk of similar styrofoam.

A 4 inch diameter disk of 1 inch-thick closed-cell styrofoam with a very small centered hole is jammed into the inside base of the funnel. The tip of a 9 inch pipet is then passed through the disk from the outside base of the funnel so that the wide bottom half of the pipet sticks out of the funnel base (Fig.1). With this type of pipet, 4 inch of the tip projects inside the funnel. The disk acts as a support for the pipet and keeps the pipet in the center line of the funnel. An ice-cream container conveniently fits over the outside base of the funnel to protect the pipet from breakage.

With the foam disk and pipet in place at the base of the funnel a square piece of background paper, 5-7 inch on a side with a central hole for the pipet to pass through, is pushed down to touch the block. Because the paper is larger than the block it can be deformed into the shape of a shallow bowl with the bottom center touching the block and the edges curving up onto the funnel. Stick the 4 corners of the paper to the funnel with Scotch tape. Such a concave surface greatly reduces shadows. The paper is easily replaceable and thus a variety of colours can be used; darker for a light moth, lighter for a dark moth.

A spread moth is simply pinned into the glass tubing (Fig. 2). If the pin is extremely loose in the pipet (a #0 pin for example) or if the moth rotates to an unacceptable angle, carefully force some modelling clay (available from most toy stores) into the tip of the pipet BEFORE the pin is inserted.

Final Set-up

I place the light-box described above on a table and use a digital camera on a table-top tripod equipped with a focusing rail (Fig. 3).

Fig. 3. Final set-up showing position of lamps and table-top tripod. Focusing rail rotated 90 degrees to show detail. In use, the focusing rail is rotated to point towards the moth.

Results

The Arctiid image, Fig.4, is exactly how it was captured by a digital camera that had its white balance pre-set to the above system. Normally, I would completely fill the frame with an image this size but purposely left a lot of white space around the image to show the total absence of shadow. There IS a gradation of illumination from the top left corner to the bottom right - caused by my sloppiness in not accurately positioning the lamps - easily corrected in Photoshop.

Fig. 4. An actual image using the above set-up, completely un-retouched except that it has been compressed from its original 14MB .tif format to a 100K .jpg (with consequential loss of image quality). Note the total absence of shadow.

APPENDIX: List of components, with ideas for alternatives

  1. 2, 20-watts Sylvania Gro-Lux Daylight Electronic Compact Fluorescent bulbs with built-in reflectors. These bulbs give excellent colour fidelity with my camera's white balance pre-set. They produce an even soft light. Although designated as ''daylight'' the bulbs do not give satisfactory colours with 35 mm daylight film. Substituting 2 electronic flashes with diffusers for the bulbs will give correct colours with such film. 2 gooseneck lamps with wide lamp holders that accommodate the above bulbs. The flexibility of the stems allows for easy orientation and adjustment of the bulbs.

  2. Plastic funnel, 16 inch top diameter, 4 inch bottom diam, 10 inch high, white inside. This is the light-box. I consider the funnel a critical part of the technique. My feeling is that the surfaces of the light-box should converge towards the moth to concentrate the light. The actual shape of the funnel is not critical, a 4-sided pyramid works equally well. The limiting factor for the funnel/pyramid is the diameter/width of the widest opening. The built-in reflectors of the bulbs have a diameter of 5 inch, 2 bulbs therefor occupy 10 inches of opening. Space between the reflectors has to be wide enough to accommodate the camera lens. Six inches is enough for my digital camera, a SLR with macro-lens may require a couple of inches more.

  3. 16 inch x 24 inch sheet of 1/4 inch plywood with a 13 inch diam. hole, and an L-shaped base for supporting the funnel horizontally.

  4. 9 inch long disposable glass pipet. I consider the pipet a critical part of the technique. This is the most difficult requirement for the average collector who has no access to a scientific laboratory. These pipets break easily and if you have access to this type of pipet buy a package of 100.

  5. 1 inch-thick closed-cell styrofoam insulation, 4 inch diam. disk

  6. 5-7 inch square of background paper, white or coloured, to form a concave surface inside the funnel.

  7. Table-top tripod with adjustable legs and centre-post. Such a small tripod in capable of holding a digital camera but would be too small for a SLR with macro-lens.

  8. Focusing rail. Very useful accessory that allows for minute adjustments in both longitudinal and horizontal planes. Another advantage is that it allows the camera to be moved forward 3.5 inch from the tripod head. The camera lens can be projected into the funnel to get closer to the moth; a useful feature when photographing a small moth.

  9. Digital camera with close-focus capability, and the ability to set the white-balance for different light sources.