Amber often contains insects that have been trapped for millions of years, yet are perfectly preserved. Focus stacking with microscope objectives is ideal for bringing them back to life – at least virtually.
Yes, I admit it, I am an evolution enthusiast. I have always been fascinated by evolution, to a great extent. As far back as I can remember, I have been excited by the interactions of various life forms adapting to each other, living together and also off each other. In the coral reef, in the forest, in the meadow, in the garden, and really everywhere.
Evolutionary changes are ubiquitous. Dinosaurs become pterosaurs and conquer a new element, the air, to survive. Pterosaurs evolve into birds that occupy every conceivable ecological niche, and birds eventually become penguins, conquering another new element, the ocean. Adaptation is everywhere. Fungi interact with trees, bees with flowers, ants with aphids, gut bacteria with humans – the list is endless. These radical and ingenious adaptations run through the entire course of evolution and have ultimately generated us humans.
Microphotography with Focus Stacking as a Time Machine?
Photographing amber inclusions – the tiny insects or plant parts that were trapped in tree resin during their lifetime and perfectly preserved – allows us to glimpse into times long before Australopithecus and older precursors of humans existed. Insects trapped in amber are evolutionary documents from the logbook of evolution!
Today, after countless generations of humans, we – you and I – are the first Homo sapiens in human history to have the technology in our living rooms or hobby rooms to photographically document these tens of millions of years old witnesses of evolution in minute detail!
Insects trapped for twenty, forty, or even a hundred million years are better preserved than any mummy. Snatched from life when they touched a sticky drop of tree resin, they squirmed deeper into the sticky mass and were hopelessly trapped. They have survived entire geological ages, perfectly preserved, and we can now embark on a journey back in time with our microscope objectives and the relatively new focus stacking technique.
I extend my heartfelt thanks to Alexander Beigel, who came to see me out for a focus stacking workshop and shared his over two-decade-long passion for creating microphotos of amber inclusions. This photographic technique is ideally suited for this purpose, and he also lent me amber pieces for my first attempts, during which I followed his advice to photograph them underwater.
However, I modified his vertical approach, where he uses a water-filled dish to capture the amber from above through the water surface, and implemented it horizontally. This helped me avoid the optical distortion effects of the water surface, which become visible with even the tiniest vibrations.
Why Photograph Underwater?
Of course, you can photograph an amber inclusion dry, i.e., without water. However, you will face varying refractive indices on an irregular surface. The density of amber differs from the air between the amber and the objective lens. This means that light refraction is different before the amber and inside it. Additionally, you would likely struggle with reflections on the polished, usually convex surface of the amber. To top it off, tiny micro-scratches on the surface would become visible.
Water has a refractive index quite similar to amber. When amber is submerged in water, it forms a light-physical unit with the liquid, and the change in the refractive index occurs at a plane parallel to the objective lenses or the camera sensor. In the vertical method, this is the water surface; in my horizontal method, it's the glass pane. This way, you avoid any light reflection on the amber surface, and micro-scratches are practically invisible as the tiny depressions they cause are filled with water.
What follows is the layer-by-layer shooting with a shifted focal plane that you are used to with focus stacking microphotography.
Photographic Technique
As mentioned, you can photograph amber inclusions both vertically and horizontally. Personally, I prefer working horizontally, except when photographing snowflakes (which will also be the subject of a blog post), where I prefer the vertical method.
Admittedly, photographing in a liquid medium like water is simpler vertically because you can use a dish and photograph through the water surface. However, I find the optical distortion effects of the water surface disturbing. Moreover, with vertical work, you must wait for the moving water surface to settle after each shot, at least if you're using a mechanical shutter that moves material and causes vibrations.
Inverted Microscope
A theoretical alternative is an inverted microscope, designed for imaging in liquid media, such as in cancer research. You place a dish with a scratch-free glass bottom on the stage, filled with water containing the amber.
The shift of the focal plane from shot to shot is done manually with a fine adjustment or with a connected motor unit that is linked to a control device, something that can greatly optimize photography with any light microscope (I intend to cover this topic in a separate blog post).
Horizontal Photography
However, my preferred method is horizontal photography. For this, I use a special glass container resembling a miniature aquarium. It allows me to fix the amber pieces underwater in a specific position and photograph them through a very thin glass pane.
Conveniently, this mini-aquarium even allows me to work on multiple amber pieces or inclusions in one go, as long as they are next to each other behind the same or even different panes. In the latter case, the container is simply rotated.
Attaching the amber pieces is quite simple. I use nano tape, a double-sided adhesive tape available on rolls in different widths, which even retains its adhesion underwater after being applied dry before. A narrow piece is stuck directly in front of one of the side panes on the bottom pane to place the amber in the desired position. Then, fill the container with water and blow away any tiny gas bubbles that form with a pipette.
You probably can't buy the tank itself anywhere, but I make this aid very simply from the glass panes of medium-format slide frames, which are glued together with silicone as is usual in aquarium construction.
The Diffuser
Many amber pieces have internal stress cracks that create diffuse light refraction. These are caused by pressure on the solidified amber material, especially terrestrial amber found in the ground, subjected to physical forces through soil movement.
These stress cracks create diffuse brightening in the photo, often with interference colors. (Here you can read how they are created.) This is certainly a fascinating phenomenon if you focus on it, but here the subject is the trapped insects, and such effects are distracting. You can largely avoid this by using a good light diffuser.
The more concentrated your light beam, the more pronounced the unwanted light refraction effects. So, you need to scatter your light as well as possible, and the effects are usually gone. If some remain, often rotating the amber slightly helps, so the light reflection is no longer visible to the lens. You just need to rotate the tiny glass container a bit, and if you work with a separate monitor in live-view mode (which I always do), you can see the effect immediately, before the first shot.
What Magnification?
Focus stacking photos of amber inclusions usually require more than a macro lens can provide. If you want to see details, a magnification of 1:1 is not enough for a 3 or 4-millimeter insect. It might cover larger creatures like a bug, which can be 15, 20, or more millimeters long in amber. Most insects in fossilized tree resin are much smaller, likely because they didn’t have the strength to pull a resin-covered body part out of the sticky mass or were blown to their doom by a gust of wind. Body lengths of 2 to 4 millimeters are very common, and some inclusions are even smaller.
I mainly use a Mitutoyo M Plan Apo 5x or 10x, depending on the size of the inclusions. Higher magnifications (20x, 50x) have always been problematic for me because such detailed shots at higher magnification showed significant blurring, greatly reducing quality, even in honey-colored but otherwise clear amber. This might be different with other amber types or different lighting since amber fluoresces under UV light, visible as noticeable material clouding. Just experiment and see.
What is Amber?
Amber is fossilized tree resin released by trees in ancient geological times when injured. Depending on its geographic origin, its age can be estimated quite accurately because we now know when and where large forests existed in the past.
Baltic amber is found in countries bordering the Baltic Sea (Germany, Denmark, Sweden, Finland, Estonia, Latvia, Lithuania, and Poland). It comes from forests on the Scandinavian Peninsula and is estimated to be 36 to 54 million years old (Eocene epoch).
Bitterfeld amber, unearthed by brown coal mining and later mined intentionally, comes from forests west of today’s city of Leipzig in the Miocene epoch. It is about 20 million years old and contains a great variety of animal inclusions.
Burmese amber or amber from Myanmar is particularly old at 100 million years, dating back to the Cretaceous period. These stones sometimes contain small vertebrates like lizards, in addition to insect inclusions.
Chinese amber comes from different geological periods. For example, it formed 50 to 53 million years ago in today’s Liaoning Province, while in Yunnan Province, it is much younger, 15 to 20 million years old.
Dominican amber is 15 to 20 million years old (Miocene Epoch) and is often clearer and more inclusion-rich than other types of amber.
Mexican amber mainly comes from the Chiapas region. It is 22 to 30 million years old (Miocene Epoch) and is particularly known for its clarity, which is very advantageous for photographic work. Many insects and plant parts are included.
How to Identify Genuine Amber
When purchasing amber with inclusions online, you should always be aware that fake products can also be offered. Be especially cautious with very cheap specimens that show extremely beautiful insect inclusions and seem like a particularly affordable opportunity. It is like in real life: if something is too good to be true, it usually isn’t true. In some cases, it is simply honey-colored synthetic resin with an insect embedded in it, which is by no means millions of years old, but much younger than you are.
What Can You Do to Verify Authenticity?
You can hardly determine the age based on the enclosed insect; that would only be possible for absolute specialists. But the inclusion material reveals a lot about its origin when approached correctly:
Genuine amber floats in saltwater (0.5 liters of water and four tablespoons or 170 grams of table salt). Stones or glass sink to the bottom, while amber floats on top.
Many plastics dissolve in acetone. Rub the surface of the material with a cotton swab soaked in acetone-containing nail polish remover. If it is amber, nothing will rub off; if it is synthetic resin, it might.
Amber becomes statically charged when rubbed with natural fibers like cotton or silk. Tiny pieces of paper will then be attracted, which does not happen with glass.
Amber emits a woody-resinous smell when heated, which is absent in synthetic resin or glass.
Amber is flammable and can be ignited. However, since you probably do not want to sacrifice it for the test, you can poke it with a very hot needle in an inconspicuous spot. Amber reacts by producing smoke, which is particularly noticeable against a black surface.
Amber develops fluorescence under ultraviolet radiation. Illuminate the stone with a special lamp that emits UV radiation, and the honey yellow changes to a bluish or greenish-white hue, and the stone looks milky.
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