Dust.
Thanks guys, appreciate the responsesDust is so hard to avoid! When photographing diamonds and jewelry, we make it a point never to touch the jewelry with our bare hands to avoid damaging the extra fine polish that we have on our pieces. We will use rubber tipped tweezers to hold the jewelry and steam it clean within a minute of putting it in the photobox and so often as we are focusing we see...
DUST! The very act of blowing the dust off the jewel sets dust to flying and it quickly seems almost magnetically attracted to whatever we are trying to photograph. The two specs that you circle in your diamond picture both appear to be dust to me, I have tens of thousands of their twins here in my photography box.
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