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Thanks Cyrus.

I used the Olympus 60mm macro with 26mm of extension tubes and a 2x converter lens to shoot the first two images. This gives me roughly a 7 times magnification in full frame terms or put another way I can shoot something that is 5mm across that will fill the entire width of the image sensor. The 60mm macro lens, which I paid £300 a few years ago, on its own can capture something that is 17mm across.

I believe you use a smartphone (which will have a smaller sensor) so 100mm lens should give you lots of magnification.

Check out the camera and lens sections in my equipment post here https://peakd.com/hive-101587/@brianhphotos/focus-stacking-tutorial-part-4-equipment which might be useful for you.