Stepping up the macro game

Since I started my daily geological materials posts on social media a couple of weeks ago, I’ve constantly been thinking and researching ways to improve the quality of my mineral macro shots. I have a decent basic Canon full frame set-up of 6D (v.1) with a 100 mm 2.8/L macro lens and have been using external LED elements for main lighting but many of the objects I want to take pictures of still do not yield to the physical restrictions of optical realities.

Main issue in macro photography is the focal depth that very much starts to become an issue in the cm-scales of mineral samples. For focal depth you need more light but long exposures make magnified shots prone to shaking and other external problems. The basic set-up just hasn’t been enough to achieve all the things I’ve wanted to image and I’ve constantly been looking at some alternatives to improve the situation.

In mid-September, we took the first year students to the traditional “freshman” field trip in Southeastern Finland. One of the stops on the trip is a gem-quality topaz quarry around the town of Kotka, which has been quarried by several mineral clubs on and off for the past decades. I remember going there with my tutors when I started my studies as well.

The quarry is located in the Kymi topaz granite stock, which is associated with the ca. 1.64 Ga Wiborg area rapakivi magmatism (you can read more about rapakivi granites for example here), and it is possible to find nice amazonite, fluorite, dendritic biotite, and even beryl samples there. The main attraction, however, is the slightly bluish and, at its best, transparent gem-quality topaz. For many years, the yield of the annual trip has not been very good as most of the good samples have already been hounded from the surface and no one has been doing any recent blasting at the site. This year turned out to be a bit different…

Three of the students were able to find some very nice, rather clear and euhedral topaz crystals. The largest one was a 1,4 cm long stubby crystal, with at least five prisms {110}, {120}, {110}, {210}, and {011}, 2 or 3 bipyramides {111}, {221}, and possibly {112}, and a terminating pinacoid {001}.

I was allowed to loan the crystal to take some shots but was again not happy with the way the first round of images turned out so I was finally motivated to invest a bit to get the shot I wanted. I ended up ordering a ring flash, extension tube set, and an adjustable macro rail in order to fine-tune the focal depth for focus stacking. Below you can see some results. There is always room for improvement especially in the far end of the focus range, but with this, I already start to be quite satisfied…

Canon 6D; 100 mm 2.8/L macro; GENESIS GMR-150 macro rail; Viltrox extension tubes: 12+20+36 mm; Meike FC110 ring flash (LED-mode); ISO160, F/6.3, 1/30; focus stack of seven images (Adobe PS edits). Length of crystal: 1.4 cm.