Diffusers and Results

The creation of a light source that can be distributed in the most homogeneous way around the subject we want to photograph, is an obligatory step and subject of research and subject of the most extreme research and customizations. There is practically a diffuser for every macro-photographer 😊, with the use, as we have already written in these pages, of countless tricks and tools, ranging from white napkin, printer paper and graphic design, yogurt cans, half-dissected ping-pong balls, semi-transparent plastic sheets… (I have tried them all).

The purpose is to eliminate unwanted reflections, and obtain an optimal light diffusion, not unidirectional, without shadows, and without extreme contrasts. In this page I show the results obtained by using as a subject some quartz crystals coming from an eocenic sand, and a parasitic wasp in which the ocelli and composite eyes are clearly visible. Some quartz grains are rounded by the mechanical erosion occurred during the long transport, others show sharp angles and flat surfaces, index of the source rock is closer to the place where the sedimentation took place. The aim is to highlight how the use of different diffusers allows to eliminate unidirectional light, partially or completely. This is sometimes at the expense of a “flattening” of the image itself, but this is what is generally sought, even though in particular situations, the accentuation of the relief (and therefore the presence of incident and unidirectional light) allows us to highlight structures, especially if we photograph microfossils or subjects that have a particular surface, with the presence of nodes, pustules, channels, ridges…

The use of a diffuser implies a lower transmission of light from the source, which varies according to the support used, the thickness, the internal structure of the diffuser. As a consequence, this will require longer acquisition times and, as a result, also be subject to environmental micro-vibrations that could compromise the quality of the photo.

Photographs were acquired with a SONY A7R II camera, mirrorless, with a 2.5x Mitutoyo objective (push to 4.7x), saved in .ARW 16bit format, processed in Helicon Focus software and exported in .DNG format. Only a contrast balancing was performed on the images.

The first photo shows the result of the acquisition of the quartz sand, without the use of any diffuser. You can see the light reflections on the surface of the individual grains, coming from the two respective panels. We are in the presence of two obvious sources of light that illuminate the subjects with unequivocal direction. The light source is given by two 20W LED panels. The shutter speed required to acquire the set of photos (stack of 180 images) amounts to 1/60″.

The stacked image of the wasp shows how the absence of a diffuser creates unwanted reflections on the individual lenses of the insect. Shutter time used 1/40″.

Using a diffuser composed of a transparent plastic sheet (from a bottle of fresh orange juice…) wrapped with a sheet of classic white printer paper (90gr/m²), the resulting image is “softer”, the light more well distributed, although some surfaces, especially the flatter ones, are still source of bright spots and reflections that risk saturating in the white. The position of the two light sources is still partially perceptible. The presence of an obstacle blocks a certain percentage of light, which requires a longer shutter speed, in this case drop to 1/25″.

The use of a double diffuser (having the same characteristics as the previous one), in some contexts allows to distribute the light even better, transforming the interspace inside the two walls, in a virtual source of light itself. In this case you can see little difference between the image obtained below and the previous one (the space between the two walls of the two diffusers is probably too large). With the same shutter speed (always 1/25″), the crystals reflect the light less, although you can always recognize the position of the two light sources.

On the wasp there is a marked improvement in light diffusion: the reflections on the ocelli and the individual lenses of the composite eyes are eliminated, even though the positions of the two light sources can be seen. Shutter speed of 1/10″. The use of a double wall diffuser (in this case the walls are much more closer) affects the exposure time required to obtain a correct image.

In this test I used a “mini-diffuser” printed with 3D printer, which has double inner wall, and that was created (thanks Walter Biggi!) to be able to acquire sub-millimeter subjects (foraminifers, radiolarians, microfossils in general) without occupying too much space on the working surface. The upper hole is calibrated to accommodate different types of objectives. By virtue of what was written previously, the double wall acts as a light source, and in this case the subjects are illuminated in a very homogeneous way. At the expense of a good distribution of light around the subjects, however, there is a certain loss of light, requiring a shutter speed set to 1/40″. This type of diffuser obviously does not find application in subjects that exceed 5 millimeters in size, or that are incorporated in a matrix.

Below a detail of the diffusers used for microfossils, with single and double wall.

Finally, we come to the “Ferrari” of the diffusers, system created by OGGLAB and actually under testing phase. In this case, the light source is placed on the inner walls of a cylinder and separated from the subject by a PETG diffuser, I discussed about this system in detail here: https://enrico-bonino.eu/cylindric-led-lighting-system/

The diffused light in the latter case is optimal, and no reflections are observed from where the light originates. The use of a matte white plastic “hat”, which covers as a lid the nuclear furnace, allows to diffuse the light even from above and improve its performance. Last but not least, and not of secondary importance, is that the shutter speed jumps to 1/250″, allowing to reduce the detection of any micro-vibrations present in the shooting phase. An updated version of this acquisition system is still in progress and further tests will soon be published on these pages.

Using the cylindrical diffuser, we solve the problems on the presence of directional light that is consequently distributed evenly. Exposure times in this case go down to 1/125″ and the contrast on the fine details of some bristles is better.

The following image shows a detail of the wasp’s right eye, acquired without, with double diffuser and in the nuclear furnace.

More detailed information are available in the Holy Grail website of the extreme macro:

Happy stacking!

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