I have both ports and both lenses and have been to Lembeh (although not with the OMD EM5, but with a Nikon D200). I have also used the Subsee +5 and +10 diopters with the M77 flip diopter ring. You can easily use the 60 mm lens in the 12-50 port without any problem. I definitely would not buy the 60 mm port. The 60 mm lens functions much like the 105 mm lens in the 1.5 crop factor cameras. The 12-50 mmn lens functions more like the 60 mm lens in the 1.5 crop factor cameras. So which one you like will depend on what you like to shoot. I couldn't get the +10 diopter to work with the 12-50 lens (at it's maximum focal length) without some vignetting. Also you have to get so close, you will be touching the subject. For me, the diopters are only useful on the 60 mm lens. The +5 on the 60 mm lens didn't seem to provide much more difference in magnification from the 60 mm lens by itself. So my configuration is the 12-50 port, 60 mm lens, and+10 diopter. Now that I've said all of this, I've only shot about 3 dives with this set-up. I took it with me to Raja Ampat last month, but found 12-50 and my wide angle lenses more useful. Going to Lembeh, you will definitely use the 60 mm lens.......and probably the diopter. Hope this is helpful.
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