macroring1 wrote:Thank you for the response.
Just one last question, how do I do with the shadows that occur at certain places? With the new light box they are reduced compared to before but some still are there. On the two examples up there there is no shaddow anywhere. How is this achieved? I even added a white panel around my lens (cutout from an old light box)
Shall I try with a tele lense from further away or staying with my 100mm L macro is my best option?
I am not sure we are talking about the same thing, but in my experience the "shadows" are reflections of surrounding dark objects on mirrored/polished surfaces of the subject. You can eliminate them with a light cube/tent that completely surrounds the subject, except for the reflections of the dark front of the lens (mostly the front element itself).
You can indeed reduce somewhat the size of this particular reflection by using a lens of long focal length, as long as you have enough space inside the light tent/cube, but this is not effective if you replace the lens with one of longer focal length but equal speed. For example, if you replace a 50 mm f/2.8 lens with a 300 mm f/2.8, the much larger front element of the 300 mm will largely negate the advantage of the increased subject-to-lens distance. Using a 300 mm f/4 (or even a 300 mm f/5.6 or f/8, assuming you can find one) will be better. Finding a large enough light tent is the next problem.
I remember one or more of the habitual posters on this site experimenting with a beam splitter to eliminate this type of reflection in macrophotography of shiny convex beetles. The principle is using the beam splitter in front of the lens to provide a coaxial illumination of the subject, adjusted in intensity to match the illumination through the light tent/diffuser (in principle, the goal is to completely surround the subject with a uniform light source, without a dark opening for the lens). This is the only way I know of to eliminate this type of dark reflection, but in practice it is difficult to get everything right. It may also reduce the image contrast through flare from the beam splitter surfaces, especially if an uncoated beam splitter is used, like a microscope cover glass. It may potentially also introduce some optical aberrations, although probably not a noticeable problem with a lens stopped down to f/8-f/11 and focused in the close-up range.
Other traditional ways that may help to reduce the dark reflections are experimenting with different amounts of tilt of the subject to try and find an orientation that minimizes the problem, and retouching the dark reflections away in post-processing.