PHOTOGRAPHING MOTHS
There is lots of good advice on the web about photographing birds in the field. There is much less information on techniques for photographing moths and I have learned a lot by trial and error…quite a lot of error, in fact. So, it seems apposite to put some of that learning back, concentrating on things that I wish I had known without the process of discovery by experiment.
So, you want to photograph moths?
I am assuming that the moths are “acquired” via a mercury vapour light trap; indeed if you want to study moths, that is a prime requirement.
When you go to your MV trap in the morning, examine the surrounding area and the outside surfaces of the trap, before you open it. Some species will not enter the trap and can be found resting outside; this is particularly true of small geometrids. If you try to move these, they will usually fly off, so they must be photographed in situ. To produce a “record” shot (i.e. the quality doesn’t matter much) for identification, the best option is to hand-hold the camera and get the job done. But if you want quality, then you need to use a tripod and cable release as described below, so the first stage is often to manoeuvre things around and get quality images of moths resting outside the trap without disturbing them. That done, you move the trap to a convenient place and begin to examine the contents.
Larger geometrids and moths of other genera are mostly passive and can be gently coaxed onto a photogenic surface. Initially I used logs, because they are steady in wind, they give good grip for the moths and provide a rustic backdrop, but sometimes the background detail spoils the image. So more recently I have transferred the moths to containers (see below for more detail), because these give a less distracting background. If the moths are frisky, then I always use a container.
This means that I have two basic set-ups. If using logs, I position these at an angle as shown in the picture below, then angle the camera on its tripod and position subject and camera so that the plane of focus of moth and image sensor are as close to parallel as possible; this ensures that all of the image will be sharp. For moths in containers the procedure is completely different and will be described later.
This is the basic setup for use with logs as background. The moth is cajoled onto the log in front
of the lens. Illumination comes from natural daylight plus the MV lamp to the left, with the reflector
positioned to even out the light from the lamp. Exposure is made with a cable release (not shown).
You need a macro lens. Without that, the image is too small and massive cropping is required to give adequate enlargement. Obviously detail is lost.
With a macro lens, the depth of field is minute, so as small an aperture as possible is essential. It pays to know the aperture of your lens at which diffraction begins to soften the image; see here, for example, for an explanation of this phenomenon and here for a procedure to determine the diffraction of your own lens. I use a Sigma 150mm 1:2.8 Apo Macro DG HSM lens, which for me is perfect. This lens begins to show diffraction at f16, so f13 is my optimum aperture. Having discovered that, you have to function in what might be called a triangle of difficulty, optimising ISO setting, shutter speed and available light.
Most moths have wings with detailed patterning, so noise is less of a problem than with smooth, clear surfaces. I find that 400 ISO gives noise on my Canon 7D that is completely manageable and can be easily corrected, provided that the exposure is right.
Do not be frightened of the need to use slow shutter speeds, provided that the moth is still – if that is a problem, see below. You MUST use a tripod and cable release. These allow perfectly sharp pictures at very low shutter speeds. There are sharp images on this site that were taken at 1/30th of a second.
Light is not a problem. If you use flash, you need a sophisticated flashgun, preferably with two heads (to prevent bias and shadow) fitted with diffusers. These are expensive. They are wonderful for butterflies or other active insects, but unnecessary for stationary moths. Remember that you already have an excellent source of illumination – you used it to attract the moths in the first place. So if the ambient light is very dull, switch on your MV lamp, place it next to your moth – about 2 feet away is fine and use a reflector on the other side of the moth to balance the light. You can buy reflectors, but a square of cooking foil scrunched up, flattened out again and taped to a piece of card is fine. You will see the light it reflects by moving the card about and targeting the reflection on the moth. Remember that, if the light from the MV lamp dominates the illumination, you may need to adjust the colour temperature in Photoshop to register the moth's colours accurately. This is another argument for shooting RAW images and for allowing subsequent adjustment of white balance. The one situation when light is a problem is paradoxical – bright sunlight is a nuisance. First, it gives stark illumination and colours are bleached out in the image. Second, it warms up the moths and they become restive.
What do you do with frisky moths? As stated above, you need a transparent container, coax the moth into it and put it in the fridge for an hour. This does not harm the moth, which will calm down. You can coat the bottom of the container with a suitable background surface so that you do not have to remove the moth to photograph it. As shown in the picture, I use frozen fruit containers and coat the bottom with mixtures of tiling grout, Polyfiller and compost. As well as providing a neutral background, this layer keeps cool and stops the moths warming up quickly and becoming frisky again.
The Cooler. This plastic box previously contained 'summer fruits' from a well-known
supermarket. The base contains a 50:50 mix of grey Polyfiller and potting compost.
It sets hard and forms a featureless rough base, which retains the low temperature
from the fridge and keeps the moth cool, calm and still whilst you photograph it in
the box.
When cooled down in this fashion some moths will not cling to the background if the box is at an angle, they just slide down, so for containers I use a different set-up. My tripod allows me to invert the head and mount the camera so that it faces directly downward (see picture). Thus I can place the container on the floor.
This is the set-up for moths in containers. Most good tripods allow the head to be inverted as shown.
The moth is in the container below, the lid is removed, reflector adjusted and the image focussed.
I always use manual focussing for moths. My camera has Live View (Canon jargon for the ability to view the live image on the rear screen, rather than the viewfinder), which is an asset. This means that I can compose the field of view, lift the mirror to Live View, magnify the image 5 times and then focus very precisely. This gives much better results than any autofocussing. I also regularly use focus stacking to get images in which all parts of the moth are sharp. This technique is explained on the Image Processing page of this site.
Finally, always sharpen the image in the computer. I find that moths give the clearest demonstration of the value of Unsharp Mask in Photoshop. To sharpen a TIFF file of a moth image I take the following steps. Magnify the image to actual pixels, open up Unsharp Mask (Filter>Sharpen). Set Amount to about 300% and start with minimum Radius (0.1) and Threshold (0). Increase the Radius stepwise until you just have maximal sharpness (usually to 0.3-0.4 pixels), then, if this has introduced edge noise, take the Threshold up to 1 or 2. I find that this always improves the RAW image considerably.
Last of all, ALWAYS release your moths into dense foliage and watch out for Robins and Magpies. These birds are smart and will quickly associate your activities with a free breakfast. I remember talking to the gardener of a hotel, who told me that Magpies inspected the hotel sign each morning because moths were attracted to its illumination at night and rested on or near the sign at dawn. I have seen Magpies trying to get at the moths visible through the transparent lid of my trap. Fortunately, they cannot do so and it drives them crazy until they give up and go away.
I hope these points help and wish you good mothing. Please mail any comments or recommended modifications.